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• Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

  - by vmiazzo

  Hi, Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not good for high availability. When 1 IP goes down clients will continue to use it for minutes. A load balancer is often suggested as a better choice. Both claims are not completely true: When the traffic is HTTP then, most of the HTML browsers are able to automatically try the next A record if the previous is down, without a new DNS look-up. Read here chapter 3.1 and here. When multiple data centers are involved then, DNS RR is the only option to distribute traffic across them. So, is it true that, with multiple data centers and HTTP traffic, the use of DNS RR is the ONLY way to assure instant fail-over when one data center goes down? Thanks, Valentino Edit: Off course each data center has a local Load Balancer with hot spare. It's OK to sacrifice session affinity for an instant fail-over. AFAIK the only way for a DNS to suggest a data center instead of another is to reply with just the IP (or IPs) associated to that data center. If the data center becomes unreachable then all those IP are also unreachables. This means that, even if smart HTML browsers are able to instantly try another A record , all the attempts will fail until the local cache entry expires and a new DNS lookup is done, fetching the new working IPs (I assume DNS automatically suggests to a new data center when one fail). So, "smart DNS" cannot assure instant fail-over. Conversely a DNS round-robin permits it. When one data center fail, the smart HTML browsers (most of them) instantly try the other cached A records jumping to another (working) data center. So, DNS round-robin doesn't assure session affinity or the lowest RTT but seems to be the only way to assure instant fail-over when the clients are "smart" HTML browsers. Edit 2: Some people suggest TCP Anycast as a definitive solution. In this paper (chapter 6) is explained that Anycast fail-over is related to BGP convergence. For this reason Anycast can employ from 15 minutes to 20 seconds to complete. 20 seconds are possible on networks where the topology was optimized for this. Probably just CDN operators can grant such fast fail-overs. Edit 3:* I did some DNS look-ups and traceroutes (maybe some expert can double check) and: The only CDN using TCP Anycast seems to be CacheFly, other operators like CDN networks and BitGravity use CacheFly. Seems that their edges cannot be used as reverse proxies. Therefore, they cannot be used to grant instant failover. Akamai and LimeLight seems to use geo-aware DNS. But! They return multiple A records. From traceroutes seems that the returned IPs are on the same data center. So, I'm puzzled on how they can offer a 100% SLA when one data center goes down.

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• Command-line video editing in Linux (cut, join and preview)

  - by sdaau

  I have rather simple editing needs - I need to cut up some videos, maybe insert some PNGs in between them, and join these videos (don't need transitions, effects, etc.). Basically, pitivi would do what I want - except, I use 640x480 30 fps AVI's from a camera, and as soon as I put in over a couple of minutes of that kind of material, pitivi starts freezing on preview, and thus becomes unusable. So, I started looking for a command line tool for Linux; I guess only ffmpeg (command line - Using ffmpeg to cut up video - Super User) and mplayer (Sam - Edit video file with mencoder under linux) are so far candidates, but I cannot find examples of the use I have in mind.   Basically, I'd imagine there's an encoder and player tools (like ffmpeg vs ffplay; or mencoder vs mplayer) - such that, to begin with, the edit sequence could be specified directly on the command line, preferably with frame resolution - a pseudocode would look like: videnctool -compose --file=vid1.avi --start=00:00:30:12 --end=00:01:45:00 --file=vid2.avi --start=00:05:00:00 --end=00:07:12:25 --file=mypicture.png --duration=00:00:02:00 --file=vid3.avi --start=00:02:00:00 --end=00:02:45:10 --output=editedvid.avi ... or, it could have a "playlist" text file, like: vid1.avi 00:00:30:12 00:01:45:00 vid2.avi 00:05:00:00 00:07:12:25 mypicture.png - 00:00:02:00 vid3.avi 00:02:00:00 00:02:45:10 ... so it could be called with videnctool -compose --playlist=playlist.txt --output=editedvid.avi The idea here would be that all of the videos are in the same format - allowing the tool to avoid transcoding, and just do a "raw copy" instead (as in mencoder's copy codec: "-oac copy -ovc copy") - or in lack of that, uncompressed audio/video would be OK (although it would eat a bit of space). In the case of the still image, the tool would use the encoding set by the video files.   The thing is, I can so far see that mencoder and ffmpeg can operate on individual files; e.g. cut a single section from a single file, or join files (mencoder also has Edit Decision Lists (EDL), which can be used to do frame-exact cutting - so you can define multiple cut regions, but it's again attributed to a single file). Which implies I have to work on cutting pieces first from individual files first (each of which would demand own temporary file on disk), and then joining them in a final video file. I would then imagine, that there is a corresponding player tool, which can read the same command line option format / playlist file as the encoding tool - except it will not generate an output file, but instead play the video; e.g. in pseudocode: vidplaytool --playlist=playlist.txt --start=00:01:14 --end=00:03:13 ... and, given there's enough memory, it would generate a low-res video preview in RAM, and play it back in a window, while offering some limited interaction ( like mplayer's keyboard shortcuts for play, pause, rewind, step frame). Of course, I'd imagine the start and end times to refer to the entire playlist, and include any file that may end up in that region in the playlist. Thus, the end result of all this would be: command line operation; no temporary files while doing the editing - and also no temporary files (nor transcoding) when rendering final output... which I myself think would be nice. So, while I think that all of the above may be a bit of a stretch - does there exist anything that would approximate the workflow described above?

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• Long connection times from PHP to MySQL on EC2

  - by Erik Giberti

  I'm having an intermittent issue connecting to a database slave with InnoDB. Intermittently I get connections taking longer than 2 seconds. These servers are hosted on Amazon's EC2. The app server is PHP 5.2/Apache running on Ubuntu. The DB slave is running Percona's XtraDB 5.1 on Ubuntu 9.10. It's using an EBS Raid array for the data storage. We already use skip name resolve and bind to address 0.0.0.0. This is a stub of the PHP code that's failing $tmp = mysqli_init(); $start_time = microtime(true); $tmp-options(MYSQLI_OPT_CONNECT_TIMEOUT, 2); $tmp-real_connect($DB_SERVERS[$server]['server'], $DB_SERVERS[$server]['username'], $DB_SERVERS[$server]['password'], $DB_SERVERS[$server]['schema'], $DB_SERVERS[$server]['port']); if(mysqli_connect_errno()){ $timer = microtime(true) - $start_time; mail($errors_to,'DB connection error',$timer); } There's more than 300Mb available on the DB server for new connections and the server is nowhere near the max allowed (60 of 1,200). Loading on both servers is < 2 on 4 core m1.xlarge instances. Some highlights from the mysql config max_connections = 1200 thread_stack = 512K thread_cache_size = 1024 thread_concurrency = 16 innodb-file-per-table innodb_additional_mem_pool_size = 16M innodb_buffer_pool_size = 13G Any help on tracing the source of the slowdown is appreciated. [EDIT] I have been updating the sysctl values for the network but they don't seem to be fixing the problem. I made the following adjustments on both the database and application servers. net.ipv4.tcp_window_scaling = 1 net.ipv4.tcp_sack = 0 net.ipv4.tcp_timestamps = 0 net.ipv4.tcp_fin_timeout = 20 net.ipv4.tcp_keepalive_time = 180 net.ipv4.tcp_max_syn_backlog = 1280 net.ipv4.tcp_synack_retries = 1 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 4096 87380 16777216 net.ipv4.tcp_wmem = 4096 87380 16777216 [EDIT] Per jaimieb's suggestion, I added some tracing and captured the following data using time. This server handles about 51 queries/second at this the time of day. The connection error was raised once (at 13:06:36) during the 3 minute window outlined below. Since there was 1 failure and roughly 9,200 successful connections, I think this isn't going to produce anything meaningful in terms of reporting. Script: date /root/database_server.txt (time mysql -h database_Server -D schema_name -u appuser -p apppassword -e '') /dev/null 2 /root/database_server.txt Results: === Application Server 1 === Mon Feb 22 13:05:01 EST 2010 real 0m0.008s user 0m0.001s sys 0m0.000s Mon Feb 22 13:06:01 EST 2010 real 0m0.007s user 0m0.002s sys 0m0.000s Mon Feb 22 13:07:01 EST 2010 real 0m0.008s user 0m0.000s sys 0m0.001s === Application Server 2 === Mon Feb 22 13:05:01 EST 2010 real 0m0.009s user 0m0.000s sys 0m0.002s Mon Feb 22 13:06:01 EST 2010 real 0m0.009s user 0m0.001s sys 0m0.003s Mon Feb 22 13:07:01 EST 2010 real 0m0.008s user 0m0.000s sys 0m0.001s === Database Server === Mon Feb 22 13:05:01 EST 2010 real 0m0.016s user 0m0.000s sys 0m0.010s Mon Feb 22 13:06:01 EST 2010 real 0m0.006s user 0m0.010s sys 0m0.000s Mon Feb 22 13:07:01 EST 2010 real 0m0.016s user 0m0.000s sys 0m0.010s [EDIT] Per a suggestion received on a LinkedIn question, I tried setting the back_log value higher. We had been running the default value (50) and increased it to 150. We also raised the kernel value /proc/sys/net/core/somaxconn (maximum socket connections) to 256 on both the application and database server from the default 128. We did see some elevation in processor utilization as a result but still received connection timeouts.

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• Publishing an Excel spreadsheet using Microsoft SBS 2008 to a web page that is viewable by mobile ph

  - by Dave Heath

  I am getting well out of my “superuser” depth here and would love some support. At work we have an Excel workbook (*.xls format circa Office 2003) which maintains our “engineers” timesheet. This handles what events we are doing across the year and how many “work units” it is. As far as a workbook goes, it is fairly simple with just a few =SUM(range) cells and some linked across sheets (12 sheets, one for each month) It is stored on a server, in a folder that provides “management” with full access and “engineers” with read-only access. The workbook itself is read-only for “engineers” and full access for “management”. I think these permissions are controlled through Active Directory. The workbook is protected with a password, assumingly to allow “management” to edit it even if they are working at a terminal logged in as an “engineer”. This protection prevents “engineers” from going to certain cells to see formulae and therefore editing them. The workbook has a macro which saves and closes it ten minutes after opening. This is to stop other “management” from being locked out by any one person who has logged in with editing privileges. I hope this is making sense to someone... :S Now then, we have Microsoft Small Business Server 2008. We have a shiny new web-based login for when we are offsite so we can get to Exchange webmail and our internal site (which uses Sharepoint 3.0). “Management” would like to be able to publish this timesheet automatically after changes (they don’t want to have to do anything different to what they are currently doing) so that using an iPhone “engineers” can check on it while out of the office. I am currently having a look at “Excel Services” for Office 2007 on TechNet but I am not sure if I am running down the right garden path at the moment. < EDIT This seems to suggest that I have to have Sharepoint Server 2007, with no mention of Sharepoint 3.0... ... "MOSS builds on WSS by adding both core features as well as end user web parts" - Wikipedia entry for Microsoft Office SharePoint Server (MOSS) this is not good news... "...and using the ASP.NET APIs, web parts can be written to extend the functionality of WSS." Wikipedia entry for Windows Sharepoint Services. Could this bring back what I need? Is this good news? Do I need to start learning ASP.NET? This link here implies that we need MOSS to do what I want and the bosses say we aint' getting it. http://serverfault.com/questions/20198/what-is-some-cool-things-you-can-do-with-sharepoint-2007/22128#22128 Back to the drawing board. < /EDIT Please could someone suggest some “further reading” for me to help point me in the right direction or to put me back on the right track. Many thanks. I will try to keep this up to date with how I get on.

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• AWS Load balancer connection reset

  - by joshmmo

  I have an ELB set up with two instances. The issue I have with it is that when I do not add www. to it, the ELB just hangs. This is some info I get when I spider with wget: Spider mode enabled. Check if remote file exists. --2013-06-20 13:40:54-- http://learning.example.com/ Resolving learning.example.com... 54.xxx.x.x53, 50.xx.xxx.x71 Connecting to learning.example.com|54.xxx.x.x53|:80... connected. HTTP request sent, awaiting response... No data received. Retrying. when I add www. it works great. I have a GoDaddy SSL cert that I added to the listener section that covers 3 domains, www.learning.example.com, files.learning.example.com and learning.example.com. These are my listener settings: - HTTP 80 HTTPS 443 N/A N/A - SSL 443 SSL 443 Change canvasNew (Change) My EC2 instances are running apache2 on Ubuntu 12.04. I will be happy to post my vhosts file if needed. However, when I ran the server with the domains pointing to just one EC2 instance things worked fine. How can I fix this issue for learning.example.com? Why does www work just fine? A second question would be what is the difference between instance protocol and load balancer protocol? EDIT: Here are the dig results for learning.example.com from yesterday. I changed the DNS entry to point to one instance to make sure it was the elb. When I switch it back I will do it for www.learning.example.com ; <<>> DiG 9.9.1-P2 <<>> learning.example.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20210 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;learning.example.com. IN A ;; ANSWER SECTION: learning.example.com. 2559 IN CNAME canvas-22222222222.us-west-1.elb.amazonaws.com. canvas-22222222222.us-west-1.elb.amazonaws.com. 60 IN A 54.xxx.x.x53 canvas-22222222222.us-west-1.elb.amazonaws.com. 60 IN A 50.xx.xxx.x71 ;; Query time: 83 msec ;; SERVER: 10.x.xx.20#53(10.x.xx.20) ;; WHEN: Thu Jun 20 13:40:47 2013 ;; MSG SIZE rcvd: 137 EDIT 2: Here is some more info that might be helpful. Port Configuration: 80 (HTTP) forwarding to 443 (HTTPS) Backend Authentication: Disabled Stickiness: Disabled(edit) 443 (SSL, Certificate: canvasNew) forwarding to 443 (SSL) Backend Authentication: Disabled So I switched everything to one EC2 IP address to bypass the elb to make sure things are working. It's running great. www and the non-www url work perfectly fine. Its only when I switch things to the ELB that learning.example.com hangs and www.learning.example.com works. Hopefully you can get some ideas flowing.

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• iptables rule(s) to send openvpn traffic from clients over an sshuttle tunnel?

  - by Sam Martin

  I have an Ubuntu 12.04 box with OpenVPN. The VPN is working as expected -- clients can connect, browse the Web, etc. The OpenVPN server IP is 10.8.0.1 on tun0. On that same box, I can use sshuttle to tunnel into another network to access a Web server on 10.10.0.9. sshuttle does its magic using the following iptables commands: iptables -t nat -N sshuttle-12300 iptables -t nat -F sshuttle-12300 iptables -t nat -I OUTPUT 1 -j sshuttle-12300 iptables -t nat -I PREROUTING 1 -j sshuttle-12300 iptables -t nat -A sshuttle-12300 -j REDIRECT --dest 10.10.0.0/24 -p tcp --to-ports 12300 -m ttl ! --ttl 42 iptables -t nat -A sshuttle-12300 -j RETURN --dest 127.0.0.0/8 -p tcp Is it possible to forward traffic from OpenVPN clients over the sshuttle tunnel to the remote Web server? I'd ultimately like to be able to set up any complicated tunneling on the server, and have relatively "dumb" clients (iPad, etc.) be able to access the remote servers via OpenVPN. Below is a basic diagram of the scenario: [Edit: added output from the OpenVPN box] $ sudo iptables -nL -v -t nat Chain PREROUTING (policy ACCEPT 1498 packets, 252K bytes) pkts bytes target prot opt in out source destination 1512 253K sshuttle-12300 all -- * * 0.0.0.0/0 0.0.0.0/0 Chain INPUT (policy ACCEPT 322 packets, 58984 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 584 packets, 43241 bytes) pkts bytes target prot opt in out source destination 587 43421 sshuttle-12300 all -- * * 0.0.0.0/0 0.0.0.0/0 Chain POSTROUTING (policy ACCEPT 589 packets, 43595 bytes) pkts bytes target prot opt in out source destination 1175 76298 MASQUERADE all -- * eth0 10.8.0.0/24 0.0.0.0/0 Chain sshuttle-12300 (2 references) pkts bytes target prot opt in out source destination 17 1076 REDIRECT tcp -- * * 0.0.0.0/0 10.10.0.0/24 TTL match TTL != 42 redir ports 12300 0 0 RETURN tcp -- * * 0.0.0.0/0 127.0.0.0/8 $ sudo iptables -nL -v -t filter Chain INPUT (policy ACCEPT 97493 packets, 30M bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 131K 109M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 1370 89160 ACCEPT all -- * * 10.8.0.0/24 0.0.0.0/0 0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable [Edit 2: more OpenVPN server output] $ netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface default 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 10.8.0.0 10.8.0.2 255.255.255.0 UG 0 0 0 tun0 10.8.0.2 * 255.255.255.255 UH 0 0 0 tun0 192.168.1.0 * 255.255.255.0 U 0 0 0 eth0 [Edit 3: still more debug output] IP forwarding appears to be enabled correctly on the OpenVPN server: # find /proc/sys/net/ipv4/conf/ -name forwarding -ls -execdir cat {} \; 18926 0 -rw-r--r-- 1 root root 0 Mar 5 13:31 /proc/sys/net/ipv4/conf/all/forwarding 1 18954 0 -rw-r--r-- 1 root root 0 Mar 5 13:31 /proc/sys/net/ipv4/conf/default/forwarding 1 18978 0 -rw-r--r-- 1 root root 0 Mar 5 13:31 /proc/sys/net/ipv4/conf/eth0/forwarding 1 19003 0 -rw-r--r-- 1 root root 0 Mar 5 13:31 /proc/sys/net/ipv4/conf/lo/forwarding 1 19028 0 -rw-r--r-- 1 root root 0 Mar 5 13:31 /proc/sys/net/ipv4/conf/tun0/forwarding 1 Client routing table: $ netstat -r Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire 0/1 10.8.0.5 UGSc 8 48 tun0 default 192.168.1.1 UGSc 2 1652 en1 10.8.0.1/32 10.8.0.5 UGSc 1 0 tun0 10.8.0.5 10.8.0.6 UHr 13 0 tun0 10.10.0/24 10.8.0.5 UGSc 0 0 tun0 <snip> Traceroute from client: $ traceroute 10.10.0.9 traceroute to 10.10.0.9 (10.10.0.9), 64 hops max, 52 byte packets 1 10.8.0.1 (10.8.0.1) 5.403 ms 1.173 ms 1.086 ms 2 192.168.1.1 (192.168.1.1) 4.693 ms 2.110 ms 1.990 ms 3 l100.my-verizon-garbage (client-ext-ip) 7.453 ms 7.089 ms 6.248 ms 4 * * * 5 10.10.0.9 (10.10.0.9) 14.915 ms !N * 6.620 ms !N

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• AMD Catalyst 13.9 installation failure

  - by Simon Verbeke

  Earlier today I installed Windows 8.1, and when I wanted to go into Catalyst Control Center, I noticed some odd error of CCC not being able to display options. I then figured I needed a driver update, so I downloaded the latest drivers, version 13.9, and tried to install them. While it was trying to install the display drivers, I got a blue screen. Tried again and got the same. Then I used an uninstall tool from AMD to remove all traces of my old drivers and tried to install the new drivers. Again, a blue screen. This is all I could think of to try. Would anyone know some other things I can try? EDIT: thought I might want to include the log entry for the crash: - <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> - <System> <Provider Name="Microsoft-Windows-WER-SystemErrorReporting" Guid="{ABCE23E7-DE45-4366-8631-84FA6C525952}" EventSourceName="BugCheck" /> <EventID Qualifiers="16384">1001</EventID> <Version>0</Version> <Level>2</Level> <Task>0</Task> <Opcode>0</Opcode> <Keywords>0x80000000000000</Keywords> <TimeCreated SystemTime="2013-10-19T20:59:25.000000000Z" /> <EventRecordID>26587</EventRecordID> <Correlation /> <Execution ProcessID="0" ThreadID="0" /> <Channel>System</Channel> <Computer>Simon-PC</Computer> <Security /> </System> - <EventData> <Data Name="param1">0x0000007e (0xffffffffc0000005, 0xfffff80002a86dca, 0xffffd00025f250e8, 0xffffd00025f248f0)</Data> <Data Name="param2">C:\WINDOWS\MEMORY.DMP</Data> <Data Name="param3">101913-8953-01</Data> </EventData> </Event> Another edit: As it turns out, the graphics card isn't showing up any more in the device manager. But as far as I can tell, it is still working (the fans are spinning and my screen is plugged into that graphics card). This is solved. it appears that my graphics card is now running with a default windows driver. I also tried the forced method mentioned here: AMD Graphics Drivers won't install properly . But I still get a BSOD. Third edit: Slight succes! Managed to install version 13.4. Everything appears to be working fine now. I think I'm just going to skip version 13.9.

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• How to implement multi-source XSLT mapping in 11g BPEL

  - by [email protected]

  In SOA 11g, you can create a XSLT mapper that uses multiple sources as the input. To implement a multi-source mapper, just follow the instructions below, Drag and drop a Transform Activity to a BPEL process Double-click on the Transform Activity, the Transform dialog window appears. Add source variables by clicking the Add icon and selecting the variable and part of the variable as needed. You can select multiple input variables. The first variable represents the main XML input to the XSL mapping, while additional variables that are added here are defined in the XSL mapping as input parameters. Select the target variable and its part if available. Specify the mapper file name, the default file name is xsl/Transformation_%SEQ%.xsl, where %SEQ% represents the sequence number of the mapper. Click OK, the xls file will be opened in the graphical mode. You can map the sources to the target as usual. Open the mapper source code, you will notice the variable representing the additional source payload, is defined as the input parameter in the map source spec and body<mapSources>    <source type="XSD">      <schema location="../xsd/po.xsd"/>      <rootElement name="PurchaseOrder" namespace="http://www.oracle.com/pcbpel/po"/>    </source>    <source type="XSD">      <schema location="../xsd/customer.xsd"/>      <rootElement name="Customer" namespace="http://www.oracle.com/pcbpel/Customer"/>      <param name="v_customer" />    </source>  </mapSources>...<xsl:param name="v_customer"/> Let's take a look at the BPEL source code used to execute xslt mapper. <assign name="Transform_1">            <bpelx:annotation>                <bpelx:pattern>transformation</bpelx:pattern>            </bpelx:annotation>            <copy>                <from expression="ora:doXSLTransformForDoc('xsl/Transformation_1.xsl',bpws:getVariableData('v_po'),'v_customer',bpws:getVariableData('v_customer'))"/>                <to variable="v_invoice"/>            </copy>        </assign> You will see BPEL uses ora:doXSLTransformForDoc XPath function to execute the XSLT mapper.This function returns the result of  XSLT transformation when the xslt template matching the document. The signature of this function is  ora:doXSLTransformForDoc(template,input, [paramQName, paramValue]*).Wheretemplate is the XSLT mapper nameinput is the string representation of xml input, paramQName is the parameter defined in the xslt mapper as the additional sourceparameterValue is the additional source payload. You can add more sources to the mapper at the later stage, but you have to modify the ora:doXSLTransformForDoc in the BPEL source code and make sure it passes correct parameter and its value pair that reflects the changes in the XSLT mapper.So the best practices are : create the variables before creating the mapping file, therefore you can add multiple sources when you define the transformation in the first place, which is more straightforward than adding them later on. Review ora:doXSLTransformForDoc code in the BPEL source and make sure it passes the correct parameters to the mapper.

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• Christian Radio Locator iPhone app

  - by Tim Hibbard

  For the last three months or so I've been working on an iPhone (and iPad) app in my spare time. It all started when I took the kids to Minneapolis and had a hard time finding radio stations to listen to on the trip. I looked in the App Store for an app that would use my GPS to show me Christian radio stations nearby, but there wasn't one. So I decided to build my own. Using public information from the FCC and a few other sources, I built a database in Google docs that contains the frequency for all Christian radio stations, where the tower is located and how far the tower can reach. I also included any streaming audio information and other contact information like Facebook or Twitter that I could find. Google spreadsheets publish in JSON format (yes, really) and Xcode can automatically deserialize JSON into a properly formatted entity. This is one area that Xcode is far superior to C#. In a just a few lines of code, I can have a list of in-memory strongly typed objects from a web-based JSON feed. To accomplish the same thing natively in .NET would be much more work and wouldn't feel nearly as clean when it was said and done. The snazzy icon shown above was built by my very talented wife. She hasn't yet provided any feedback on the app's user interface, which is why it is so plain and boring. I used a navigation view controller and EGO pull to refresh table view to construct the main window. Pulling down to refresh initiates a GPS lookup, which queries the database for radio stations in range (yes, you can pass parameters to Google spreadsheets and get a subset back in JSON). Pulling up on the table extends the range of the search and includes stations that may not be close enough to get clear audio. This feature is not that intuitive and the next version contains an update to that functionality. Tapping a cell will show a detail view that displays additional information about the station. The user can click to view the station on a map, click to listen to an online stream (if available) or click to see the station's Facebook or Twitter pages. Swiping back and forth on the table changes the information that is displayed on the right hand side of the table cell. It scrolls through the city where the tower is located, how far the phone is from the tower, the range of the tower and in the next version a signal strength indicator. This was pretty easy to implement once I figured out how to assign the gesture recognizer delegate.  Tapping and holding on a cell will jump the user to the map view screen. Which is pretty cool, but very hard for even a power user to discover. To tackle the issue of discoverability, the next version has a series of instructions displayed at the bottom of the screen to show the user the various shortcuts. Once the user has performed the swipes and long holds, the instructions disappear. I've learned a lot developing this app. Spending over a decade exclusively in .NET made the learning curve a bit steep, but once I learned the structure and syntax of Objective-C, I've learned to appreciate the power and simplicity of it. Here are a few screenshots. I would really appreciate any feedback and especially iTunes reviews. Technically it is open source and a smart googler could probably find it. I just haven't promoted it as open source.     Cross posted from timhibbard.com

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• Changing the action of a hyperlink in a Silverlight RichTextArea

  - by Marc Schluper

  The title of this post could also have been "Move over Hyperlink, here comes Actionlink" or "Creating interactive text in Silverlight." But alas, there can be only one. Hyperlinks are very useful. However, they are also limited because their action is fixed: browse to a URL. This may have been adequate at the start of the Internet, but nowadays, in web applications, the one thing we do not want to happen is a complete change of context. In applications we typically like a hyperlink selection to initiate an action that updates a part of the screen. For instance, if my application has a map displayed with some text next to it, the map would react to a selection of a hyperlink in the text, e.g. by zooming in on a location and displaying additional locational information in a popup. In this way, the text becomes interactive text. It is quite common that one company creates and maintains websites for many client companies. To keep maintenance cost low, it is important that the content of these websites can be updated by the client companies themselves, without the need to involve a software engineer. To accommodate this scenario, we want the author of the interactive text to configure all hyperlinks (without writing any code). In a Silverlight RichTextArea, the default action of a Hyperlink is the same as a traditional hyperlink, but it can be changed: if the Command property has a value then upon a click event this command is called with the value of the CommandParameter as parameter. How can we let the author of the text specify a command for each hyperlink in the text, and how can we let an application react properly to a hyperlink selection event? We are talking about any command here. Obviously, the application would recognize only a specific set of commands, with well defined parameters, but the approach we take here is generic in the sense that it pertains to the RichTextArea and any command. So what do we require? We wish that: As a text author, I can configure the action of a hyperlink in a (rich) text without writing code; As a text author, I can persist the action of a hyperlink with the text; As a reader of persisted text, I can click a hyperlink and the configured action will happen; As an application developer, I can configure a control to use my application specific commands. In an excellent introduction to the RichTextArea, John Papa shows (among other things) how to persist a text created using this control. To meet our requirements, we can create a subclass of RichTextArea that uses John's code and allows plugging in two command specific components: one to prompt for a command definition, and one to execute the command. Since both of these plugins are application specific, our RichTextArea subclass should not assume anything about them except their interface. public interface IDefineCommand { void Prompt(string content, // the link content Action<string, object> callback); // the method called to convey the link definition } public interface IPerformCommand : ICommand {} The IDefineCommand plugin receives the content of the link (the text visible to the reader) and displays some kind of control that allows the author to define the link. When that's done, this (possibly changed) content string is conveyed back to the RichTextArea, together with an object that defines the command to execute when the link is clicked by the reader of the published text. The IPerformCommand plugin simply implements System.Windows.Input.ICommand. Let's use MEF to load the proper plugins. In the example solution there is a project that contains rudimentary implementations of these. The IDefineCommand plugin simply prompts for a command string (cf. a command line or query string), and the IPerformCommand plugin displays a MessageBox showing this command string. An actual application using this extended RichTextArea would have its own set of commands, each having their own parameters, and hence would provide more user friendly application specific plugins. Nonetheless, in any case a command can be persisted as a string and hence the two interfaces defined above suffice. For a Visual Studio 2010 solution, see my article on The Code Project.

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• Routes for IIS Classic and Integrated Mode

  - by imran_ku07

       Introduction:             ASP.NET MVC Routing feature makes it very easy to provide clean URLs. You just need to configure routes in global.asax file to create an application with clean URLs. In most cases you define routes works in IIS 6, IIS 7 (or IIS 7.5) Classic and Integrated mode. But in some cases your routes may only works in IIS 7 Integrated mode, like in the case of using extension less URLs in IIS 6 without a wildcard extension map. So in this article I will show you how to create different routes which works in IIS 6 and IIS 7 Classic and Integrated mode.       Description:             Let's say that you need to create an application which must work both in Classic and Integrated mode. Also you have no control to setup a wildcard extension map in IIS. So you need to create two routes. One with extension less URL for Integrated mode and one with a URL with an extension for Classic Mode.   routes.MapRoute( "DefaultClassic", // Route name "{controller}.aspx/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); routes.MapRoute( "DefaultIntegrated", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults );               Now you have set up two routes, one for Integrated mode and one for Classic mode. Now you only need to ensure that Integrated mode route should only match if the application is running in Integrated mode and Classic mode route should only match if the application is running in Classic mode. For making this work you need to create two custom constraint for Integrated and Classic mode. So replace the above routes with these routes,     routes.MapRoute( "DefaultClassic", // Route name "{controller}.aspx/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional }, // Parameter defaults new { mode = new ClassicModeConstraint() }// Constraints ); routes.MapRoute( "DefaultIntegrated", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional }, // Parameter defaults new { mode = new IntegratedModeConstraint() }// Constraints );            The first route which is for Classic mode adds a ClassicModeConstraint and second route which is for Integrated mode adds a IntegratedModeConstraint. Next you need to add the implementation of these constraint classes.     public class ClassicModeConstraint : IRouteConstraint { public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { return !HttpRuntime.UsingIntegratedPipeline; } } public class IntegratedModeConstraint : IRouteConstraint { public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { return HttpRuntime.UsingIntegratedPipeline; } }             HttpRuntime.UsingIntegratedPipeline returns true if the application is running on Integrated mode; otherwise, it returns false. So routes for Integrated mode only matched when the application is running on Integrated mode and routes for Classic mode only matched when the application is not running on Integrated mode.       Summary:             During developing applications, sometimes developers are not sure that whether this application will be host on IIS 6 or IIS 7 (or IIS 7.5) Integrated mode or Classic mode. So it's a good idea to create separate routes for both Classic and Integrated mode so that your application will use extension less URLs where possible and use URLs with an extension where it is not possible to use extension less URLs. In this article I showed you how to create separate routes for IIS Integrated and Classic mode. Hope you will enjoy this article too.   SyntaxHighlighter.all()

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• Listen to Online Radio with Antenna

  - by Asian Angel

  Are you looking for some fresh new music to listen to at home or at work? With Antenna you can listen to online radio stations from all over the world. Note: Requires Adobe AIR (download link at bottom of article). Antenna in Action Once you have completed the installation and started Antenna up this is the window that you will see. The left side will have a “browsing pane” where you can search for the stations that you would like to listen to using the various categories. Based on the stations that you choose the background map will change location to match the stations locations. Here is a closer look at the “Categories Bar”. For our first example we used the “Country Category” to find our first station to listen to. When you choose a country you will be presented with a list of the stations available for that country. To start listening to a particular station just double click on the appropriate entry line. A closer look at the “browser pane” with our first station playing. Notice the “Reliability Indicator” that will be available for each listing…some may be better than others and you can use this to choose the best streaming stations from the list. In the upper left corner you will notice three icons…each will open a small pop-up window with a specific purpose. The first icon will open up the “About Window”. If you need to contact Antenna’s creator or would like to place a request for a station to be added to the app then this is the best way to do it. The second icon will open up a Antenna specific chat window. The third icon will allow you to set a default location and make adjustments to some of the app’s settings. Recording Audio The “Recording Function” is the only area where we experienced some “quirkiness” with the app. To start recording press the “Round White Button”… Note: Based on feedback on the app creator’s webpage some people have experienced the same problem as we did during our tests with the app failing to complete the recordings. Hopefully this bug will be fixed with the next release. Once recording has started the button will turn red. Click on the button again to stop recording. Once you have stopped recording you will see the following message window appear and the main window will be shaded over with a whitish color until you click “OK”. Conclusion Regardless of the slight quirkiness in recording online music Antenna more than makes up for it with the terrific selection of online stations and streaming capability. New fresh music for you to listen to is only a click or two away… Links Download Antenna (Antenna Homepage) Download Antenna at Softpedia Download Adobe AIR Similar Articles Productive Geek Tips Listen to Local FM Radio in Windows 7 Media CenterListen to Over 100,000 Radio Stations in Windows Media CenterListen To XM Radio with Windows Media Center in Windows 7Listen and Record Over 12,000 Online Radio Stations with RadioSureWeekend Fun: Watch Television on Your PC with AnyTV TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Will it Blend? iPad Edition Penolo Lets You Share Sketches On Twitter Visit Woolyss.com for Old School Games, Music and Videos Add a Custom Title in IE using Spybot or Spyware Blaster When You Need to Hail a Taxi in NYC Live Map of Marine Traffic

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• Error while installing emacs23 from Software Center

  - by vrcmr

  Trying to install emacs in Software Center Ubuntu 12.04 got this error. installArchives() failed: Selecting previously unselected package emacs23. (Reading database ... (Reading database ... 5% (Reading database ... 10% (Reading database ... 15% (Reading database ... 20% (Reading database ... 25% (Reading database ... 30% (Reading database ... 35% (Reading database ... 40% (Reading database ... 45% (Reading database ... 50% (Reading database ... 55% (Reading database ... 60% (Reading database ... 65% (Reading database ... 70% (Reading database ... 75% (Reading database ... 80% (Reading database ... 85% (Reading database ... 90% (Reading database ... 95% (Reading database ... 100% (Reading database ... 182385 files and directories currently installed.) Unpacking emacs23 (from .../emacs23_23.3+1-1ubuntu9_i386.deb) ... Processing triggers for desktop-file-utils ... Processing triggers for bamfdaemon ... Rebuilding /usr/share/applications/bamf.index... Processing triggers for gnome-menus ... Processing triggers for man-db ... Setting up emacs23 (23.3+1-1ubuntu9) ... update-alternatives: using /usr/bin/emacs23-x to provide /usr/bin/emacs (emacs) in auto mode. emacs-install emacs23 install/dictionaries-common: Byte-compiling for emacsen flavour emacs23 Warning: Lisp directory `/usr/share/emacs/23.3/site-lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/site-lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/leim' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/leim' does not exist. Error: charsets directory (/usr/share/emacs/23.3/etc/charsets) does not exist. Emacs will not function correctly without the character map files. Please check your installation! Warning: Could not find simple.el nor simple.elc Cannot open load file: bytecomp emacs-install: /usr/lib/emacsen-common/packages/install/dictionaries-common emacs23 failed at /usr/lib/emacsen-common/emacs-install line 28, <TSORT> line 3. dpkg: error processing emacs23 (--configure): subprocess installed post-installation script returned error exit status 255 No apport report written because MaxReports is reached already Errors were encountered while processing: emacs23 Error in function: Setting up emacs23 (23.3+1-1ubuntu9) ... emacs-install emacs23 install/dictionaries-common: Byte-compiling for emacsen flavour emacs23 Warning: Lisp directory `/usr/share/emacs/23.3/site-lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/site-lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/leim' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/lisp' does not exist. Warning: Lisp directory `/usr/share/emacs/23.3/leim' does not exist. Error: charsets directory (/usr/share/emacs/23.3/etc/charsets) does not exist. Emacs will not function correctly without the character map files. Please check your installation! Warning: Could not find simple.el nor simple.elc Cannot open load file: bytecomp emacs-install: /usr/lib/emacsen-common/packages/install/dictionaries-common emacs23 failed at /usr/lib/emacsen-common/emacs-install line 28, <TSORT> line 3. dpkg: error processing emacs23 (--configure): subprocess installed post-installation script returned error exit status 255

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• Using the Onboard VGA output with a PCIe video card. Both nVidia

  - by sebikul

  I have 2 video cards, one On board, a nVidia 6150SE nForce 430 and a PCIe nVidia GeForce GT 220 1GB DDR2 RAM I have already configured the PCIe card to use the dual monitor feature, using the VGA and HDMI ports, but now I want to add a third monitor, using the On board VGA port I have managed to enable the On board graphics processor, which is taking 400MB of ram, but I cant manage to use it, nvidia-settings does not detect it, like it's not usable (but is there) My questions are the following: How can I manage to get the On board VGA display to work together with the PCIe graphics card? If possible, how can I recover those 400 MB the on board card is taking (even without being used) or how can I get it to use the PCIe card available memory? System Details: Linux 2.6.35-28-generic i686 Ubuntu 10.10 (All updates installed) NVIDIA Driver Version: 260.19.06 (Official) If more info is needed please let me know. Here is the lspci output when the On board card is disabled: 00:00.0 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a1) 00:01.0 ISA bridge: nVidia Corporation MCP61 LPC Bridge (rev a2) 00:01.1 SMBus: nVidia Corporation MCP61 SMBus (rev a2) 00:01.2 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a2) 00:01.3 Co-processor: nVidia Corporation MCP61 SMU (rev a2) 00:02.0 USB Controller: nVidia Corporation MCP61 USB Controller (rev a3) 00:02.1 USB Controller: nVidia Corporation MCP61 USB Controller (rev a3) 00:04.0 PCI bridge: nVidia Corporation MCP61 PCI bridge (rev a1) 00:05.0 Audio device: nVidia Corporation MCP61 High Definition Audio (rev a2) 00:06.0 IDE interface: nVidia Corporation MCP61 IDE (rev a2) 00:07.0 Bridge: nVidia Corporation MCP61 Ethernet (rev a2) 00:08.0 IDE interface: nVidia Corporation MCP61 SATA Controller (rev a2) 00:09.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0b.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0c.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0d.0 VGA compatible controller: nVidia Corporation C61 [GeForce 6150SE nForce 430] (rev a2) 00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control 01:09.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 08) 02:00.0 VGA compatible controller: nVidia Corporation GT216 [GeForce GT 220] (rev a2) 02:00.1 Audio device: nVidia Corporation High Definition Audio Controller (rev a1) And this is when both are enabled: 00:00.0 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a1) 00:01.0 ISA bridge: nVidia Corporation MCP61 LPC Bridge (rev a2) 00:01.1 SMBus: nVidia Corporation MCP61 SMBus (rev a2) 00:01.2 RAM memory: nVidia Corporation MCP61 Memory Controller (rev a2) 00:01.3 Co-processor: nVidia Corporation MCP61 SMU (rev a2) 00:02.0 USB Controller: nVidia Corporation MCP61 USB Controller (rev a3) 00:02.1 USB Controller: nVidia Corporation MCP61 USB Controller (rev a3) 00:04.0 PCI bridge: nVidia Corporation MCP61 PCI bridge (rev a1) 00:05.0 Audio device: nVidia Corporation MCP61 High Definition Audio (rev a2) 00:06.0 IDE interface: nVidia Corporation MCP61 IDE (rev a2) 00:07.0 Bridge: nVidia Corporation MCP61 Ethernet (rev a2) 00:08.0 IDE interface: nVidia Corporation MCP61 SATA Controller (rev a2) 00:09.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0b.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0c.0 PCI bridge: nVidia Corporation MCP61 PCI Express bridge (rev a2) 00:0d.0 VGA compatible controller: nVidia Corporation C61 [GeForce 6150SE nForce 430] (rev a2) 00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control 01:09.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 08) 02:00.0 VGA compatible controller: nVidia Corporation GT216 [GeForce GT 220] (rev a2) 02:00.1 Audio device: nVidia Corporation High Definition Audio Controller (rev a1) Output of lshw -class display: *-display description: VGA compatible controller product: GT216 [GeForce GT 220] vendor: nVidia Corporation physical id: 0 bus info: pci@0000:02:00.0 version: a2 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress vga_controller bus_master cap_list rom configuration: driver=nvidia latency=0 resources: irq:18 memory:df000000-dfffffff memory:c0000000-cfffffff memory:da000000-dbffffff ioport:ef80(size=128) memory:def80000-deffffff *-display description: VGA compatible controller product: C61 [GeForce 6150SE nForce 430] vendor: nVidia Corporation physical id: d bus info: pci@0000:00:0d.0 version: a2 width: 64 bits clock: 66MHz capabilities: pm msi vga_controller bus_master cap_list rom configuration: driver=nvidia latency=0 resources: irq:22 memory:dd000000-ddffffff memory:b0000000-bfffffff memory:dc000000-dcffffff memory:deb40000-deb5ffff If what I'm looking for is not possible, please tell me, so I can disable the On board card and recover those 400MB of wasted RAM Thanks for your help!

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• How can I back up my ubuntu system?

  - by Eloff

  I'm sure there's a lot of questions on here similar to this, and I've been reading them, but I still feel this warrants a new question. I want nightly, incremental backups (full disk images would waste a lot of space - unless compressed somehow.) Preferably rotating or deleting old backups when running out of space or after a fixed number of backups. I want to be able to quickly and painlessly restore my system from these backups. This is my first time running ubuntu as my main development machine and I know from my experience with it as a server and in virtual machines that I regularly manage to make it unbootable or damage it to the point of being unable to rescue it. So how would you recommend I do this? There are so many options out there I really don't know where to start. There seems to be a vocal school of thought that it's sufficient to backup your home directory and the list of installed packages from the package manager. I've already installed lots of things from source, or outside of the package manager (development tools, ides, compilers, graphics drivers, etc.) So at the very least, if I do not back up the operating system itself I need to grab all config files, all program binaries, all created but required files, etc. I'd rather backup too much than too little - an ubuntu install is tiny anyway. Also this drastically reduces the restore time, which would cost me more in my time than the extra storage space. I tried using Deja Dup to backup the root partition, excluding some things like /mnt /media /dev /proc etc. Although many websites assured me you can backup a running linux system this way - that seems to be false as it complained that it could not backup the following files: /boot/System.map-3.0.0-17-generic /boot/System.map-3.2.0-22-generic /boot/vmcoreinfo-3.0.0-17-generic /boot/vmlinuz-3.0.0-17-generic /boot/vmlinuz-3.2.0-22-generic /etc/.pwd.lock /etc/NetworkManager/system-connections/LAN Connection /etc/apparmor.d/cache/lightdm-guest-session /etc/apparmor.d/cache/sbin.dhclient /etc/apparmor.d/cache/usr.bin.evince /etc/apparmor.d/cache/usr.lib.telepathy /etc/apparmor.d/cache/usr.sbin.cupsd /etc/apparmor.d/cache/usr.sbin.tcpdump /etc/apt/trustdb.gpg /etc/at.deny /etc/ati/inst_path_default /etc/ati/inst_path_override /etc/chatscripts /etc/cups/ssl /etc/cups/subscriptions.conf /etc/cups/subscriptions.conf.O /etc/default/cacerts /etc/fuse.conf /etc/group- /etc/gshadow /etc/gshadow- /etc/mtab.fuselock /etc/passwd- /etc/ppp/chap-secrets /etc/ppp/pap-secrets /etc/ppp/peers /etc/security/opasswd /etc/shadow /etc/shadow- /etc/ssl/private /etc/sudoers /etc/sudoers.d/README /etc/ufw/after.rules /etc/ufw/after6.rules /etc/ufw/before.rules /etc/ufw/before6.rules /lib/ufw/user.rules /lib/ufw/user6.rules /lost+found /root /run/crond.reboot /run/cups/certs /run/lightdm /run/lock/whoopsie/lock /run/udisks /var/backups/group.bak /var/backups/gshadow.bak /var/backups/passwd.bak /var/backups/shadow.bak /var/cache/apt/archives/lock /var/cache/cups/job.cache /var/cache/cups/job.cache.O /var/cache/cups/ppds.dat /var/cache/debconf/passwords.dat /var/cache/ldconfig /var/cache/lightdm/dmrc /var/crash/_usr_lib_x86_64-linux-gnu_colord_colord.102.crash /var/lib/apt/lists/lock /var/lib/dpkg/lock /var/lib/dpkg/triggers/Lock /var/lib/lightdm /var/lib/mlocate/mlocate.db /var/lib/polkit-1 /var/lib/sudo /var/lib/urandom/random-seed /var/lib/ureadahead/pack /var/lib/ureadahead/run.pack /var/log/btmp /var/log/installer/casper.log /var/log/installer/debug /var/log/installer/partman /var/log/installer/syslog /var/log/installer/version /var/log/lightdm/lightdm.log /var/log/lightdm/x-0-greeter.log /var/log/lightdm/x-0.log /var/log/speech-dispatcher /var/log/upstart/alsa-restore.log /var/log/upstart/alsa-restore.log.1.gz /var/log/upstart/console-setup.log /var/log/upstart/console-setup.log.1.gz /var/log/upstart/container-detect.log /var/log/upstart/container-detect.log.1.gz /var/log/upstart/hybrid-gfx.log /var/log/upstart/hybrid-gfx.log.1.gz /var/log/upstart/modemmanager.log /var/log/upstart/modemmanager.log.1.gz /var/log/upstart/module-init-tools.log /var/log/upstart/module-init-tools.log.1.gz /var/log/upstart/procps-static-network-up.log /var/log/upstart/procps-static-network-up.log.1.gz /var/log/upstart/procps-virtual-filesystems.log /var/log/upstart/procps-virtual-filesystems.log.1.gz /var/log/upstart/rsyslog.log /var/log/upstart/rsyslog.log.1.gz /var/log/upstart/ureadahead.log /var/log/upstart/ureadahead.log.1.gz /var/spool/anacron/cron.daily /var/spool/anacron/cron.monthly /var/spool/anacron/cron.weekly /var/spool/cron/atjobs /var/spool/cron/atspool /var/spool/cron/crontabs /var/spool/cups

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• GCC 4.2.1 Compiling on Cygwin(Win7 64bit) for iPhone [closed]

  - by Kenneth Noland

  Hey This is going to take a long while to explain, but the short version is that I am currently attempting to compile the LLVM GCC frontend for ARMv7 to compile apps for the Cortex-A8(iPhone 3GS). I'm running into an error from LD when compiling libgcc(part of the gcc compilation process) that has been driving me mad! The command is this: /usr/llvm-gcc-4.2-2.8.source/build/./gcc/xgcc \ -B/usr/llvm-gcc-4.2_2.8.source/build/./gcc \ -B/usr/local/arm-apple-darwin/bin \ -B/usr/local/arm-apple-darwin/lib \ -isystem /usr/local/arm-apple-darwin/include \ -isystem /usr/local/arm-apple-darwin/sys-include \ -O2 -g -W -Wall -Wwrite-strings -wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -fno-inline -dynamiclib -nodefaultlibs -W1,-dead_strip \ -marm \ -install_name /usr/local/arm-apple-darwin/lib/libgcc_s.1.dylib \ -single_module -o ./libgcc_s.1.dylib.tmp \ -W1,-exported_symbols_list,libgcc/./libgcc.map -compatibility_version 1 -current_version 1.0 -DIN_GCC -DCROSS_DIRECTORY_STRUCTURE -DHAVE_GTHR_DEFAULT -DIN_LIBGCC2 -D__GCC_FLOAT_NOT_NEEDED -Dinhibit_libc \ ... long list of .o files ... \ -lc And the result is typically a lot of undefined references to malloc, free, exit, etc. which typically indicate that libc is not getting compiled in. After going through the list of errors that ld is throwing, I see at the top that it is attempting to pull in /usr/lib/libc.a and complains that it is not the correct platform. Okay, that makes sense, so I spent 5 minutes on google and found an answer. Turns out that if I copy the libSystem.dylib and rename it to libc.dylib, that should solve the problem, but it doesn't. I couldn't find a copy of that file on my phone, so I pulled it directly from the SDK. I then get this strange error: ld64: in /usr/local/arm-apple-darwin/lib/libc.dylib, can't re-map file, errno=22 At this point, I did everything I could think of. I grabbed a fresh copy of my /usr/lib folder from my iphone and confirmed that libSystem.dylib(and libSystem.B.dylib) wasn't there. I unpacked the raw .ipsw package for iOS 4.2.1 and once again, I could not find a copy of libSystem.dylib there either. I unpacked the iPhoneSDK and MacOS SDK and I managed to find a copy of it in both, but that error just kept persisting. I copied libSystem.dylib, libSystem.B.dylib, tried all sorts of combinations of renaming to libc.dylib and still nothing but errors. I can't find a way to get it to recognize the file and link against it. I also tried linking against the libc.a located in the iphone SDK and that didn't work either. I checked what ./xgcc was firing off, and it was my freshly built copy of arm-apple-darwin-ld64 which should be fine. A little bit of background here. I built LLVM+Clang 2.8 with no errors, and I rebuilt the ODCCTools with some light modifications to get it to compile on Cygwin(I'll post my changes in a patch along with a tutorial if I can get this to work). I also grabbed the iphone-dev "includes" and "csu" project and those completed successfully, although there really is no point to them since I can't get it to link against crt0.a. I'm running out of ideas here. Can anyone help me out on this?

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• Announcement: Employee Info Starter Kit (v5.0) is Released

  - by Mohammad Ashraful Alam

  Ever wanted to have a simple jQuery menu bound with ASP.NET web site map file? Ever wanted to have cool css design stuffs implemented on your ASP.NET data bound controls? Ever wanted to let Visual Studio generate logical layers for you, which can be easily tested, customized and bound with ASP.NET data controls? If your answers with respect to above questions are ‘yes’, then you will probably happy to try out latest release (v5.0) of Employee Starter Kit, which is intended to address different types of real world challenges faced by web application developers when performing common CRUD operations. Using a single database table ‘Employee’, the current release illustrates how to utilize Microsoft ASP.NET 4.0 Web Form Data Controls, Entity Framework 4.0 and Visual Studio 2010 effectively in that context. Employee Info Starter Kit is an open source ASP.NET project template that is highly influenced by the concept ‘Pareto Principle’ or 80-20 rule, where it is targeted to enable a web developer to gain 80% productivity with 20% of effort with respect to learning curve and production. This project template is titled as “Employee Info Starter Kit”, which was initially hosted on Microsoft Code Gallery and been downloaded 1, 50,000+ of copies afterword.  The latest version of this starter kit is hosted in Codeplex. Release Highlights User End Functional Specification The user end functionalities of this starter kit are pretty simple and straight forward that are focused in to perform CRUD operation on employee records as described below. Creating a new employee record Read existing employee records Update an existing employee record Delete existing employee records Architectural Overview Simple 3 layer architecture (presentation, business logic and data access layer) ASP.NET web form based user interface Built-in code generators for logical layers, implemented in Visual Studio default template engine (T4) Built-in Entity Framework entities as business entities (aka: data containers) Data Mapper design pattern based Data Access Layer, implemented in C# and Entity Framework Domain Model design pattern based Business Logic Layer, implemented in C# Object Model for Cross Cutting Concerns (such as validation, logging, exception management) Minimum System Requirements Visual Studio 2010 (Web Developer Express Edition) or higher Sql Server 2005 (Express Edition) or higher Technology Utilized Programming Languages/Scripts Browser side: JavaScript Web server side: C# Code Generation Template: T-4 Template Frameworks .NET Framework 4.0 JavaScript Framework: jQuery 1.5.1 CSS Framework: 960 grid system .NET Framework Components .NET Entity Framework .NET Optional/Named Parameters (new in .net 4.0) .NET Tuple (new in .net 4.0) .NET Extension Method .NET Lambda Expressions .NET Anonymous Type .NET Query Expressions .NET Automatically Implemented Properties .NET LINQ .NET Partial Classes and Methods .NET Generic Type .NET Nullable Type ASP.NET Meta Description and Keyword Support (new in .net 4.0) ASP.NET Routing (new in .net 4.0) ASP.NET Grid View (CSS support for sorting - (new in .net 4.0)) ASP.NET Repeater ASP.NET Form View ASP.NET Login View ASP.NET Site Map Path ASP.NET Skin ASP.NET Theme ASP.NET Master Page ASP.NET Object Data Source ASP.NET Role Based Security Getting Started Guide To see Employee Info Starter Kit in action is pretty easy! Download the latest version. Extract the file. From the extracted folder click the C# project file (Eisk.Web.csproj) to open it in Visual Studio 2010 Hit Ctrl+F5! The current release (v5.0) of Employee Info Starter Kit is properly packaged, fully documented and well tested. If you want to learn more about it in details, just check the following links: Release Home Page Installation Walkthrough Hand on Coding Walkthrough Technical Reference Enjoy!

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• Gnome Shell Theme Problem on Ubuntu 11.10

  - by Khurram Majeed

  I am trying to install ANewStart GNOME shell themes on Ubuntu 11.10. I have installed gnome shell extension for themes: sudo add-apt-repository ppa:webupd8team/gnome3 sudo apt-get update sudo apt-get install gnome-shell-extensions-user-theme I got the instructions from here ANewStart GNOME Shell Theme + AwOken Icons Theme = Pure Art. But when I go to "Advanced Settings - Shell Extensions" its empty... There is nothing. Also there is a orange triangle sign next to Shell Theme drop down in Advanced Settings - Theme. When I try to run the gnome-tweak-tool from terminal I get following error: imresh@imresh-laptop:~$ gnome-tweak-tool CRITICAL: Error parsing schema org.gnome.shell (/usr/share/glib-2.0/schemas/org.gnome.shell.gschema.xml) Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/gtweak/gsettings.py", line 45, in __init__ summary = key.getElementsByTagName("summary")[0].childNodes[0].data IndexError: list index out of range WARNING : Error detecting shell Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/gtweak/tweaks/tweak_shell_extensions.py", line 145, in __init__ shell = GnomeShellFactory().get_shell() File "/usr/lib/python2.7/dist-packages/gtweak/utils.py", line 38, in getinstance instances[cls] = cls() File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 123, in __init__ v = map(int,proxy.version.split(".")) File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 46, in version return json.loads(self.execute_js('const Config = imports.misc.config; Config.PACKAGE_VERSION')) File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 39, in execute_js result, output = self.proxy.Eval('(s)', js) File "/usr/lib/python2.7/dist-packages/gi/overrides/Gio.py", line 148, in __call__ kwargs.get('flags', 0), kwargs.get('timeout', -1), None) File "/usr/lib/python2.7/dist-packages/gi/types.py", line 43, in function return info.invoke(*args, **kwargs) GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Shell was not provided by any .service files WARNING : Shell not running Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/gtweak/tweaks/tweak_shell.py", line 57, in __init__ self._shell = GnomeShellFactory().get_shell() File "/usr/lib/python2.7/dist-packages/gtweak/utils.py", line 38, in getinstance instances[cls] = cls() File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 123, in __init__ v = map(int,proxy.version.split(".")) File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 46, in version return json.loads(self.execute_js('const Config = imports.misc.config; Config.PACKAGE_VERSION')) File "/usr/lib/python2.7/dist-packages/gtweak/gshellwrapper.py", line 39, in execute_js result, output = self.proxy.Eval('(s)', js) File "/usr/lib/python2.7/dist-packages/gi/overrides/Gio.py", line 148, in __call__ kwargs.get('flags', 0), kwargs.get('timeout', -1), None) File "/usr/lib/python2.7/dist-packages/gi/types.py", line 43, in function return info.invoke(*args, **kwargs) GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Shell was not provided by any .service files WARNING : Could not list shell extensions Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/gtweak/tweaks/tweak_shell.py", line 62, in __init__ extensions = self._shell.list_extensions() AttributeError: ShellThemeTweak instance has no attribute '_shell' (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed (gnome-tweak-tool:5323): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed Please help me in fixing this. I have also restarted the computer many times it does not make a difference.

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• Technology vs. Antiquated Methods

  - by AreYouSerious

  So Here I am talking with my Program lead, about technology, and how while my father is the VP of a major company, he still doesn't have a blackberry, or a smart phone. and I think it's funny. Most people would say it's a generational thing. That because he's older, he dosen't accept technology, and that's why. I have trouble swallowing that because this is the same man, who bought a satellite radio for his car, and made sure that the printer for the house was networked so that his and my mom's laptop could print wirelessly from the living room through their wireless network. I think it has to do with more with necessity, and partially with finical responsibility. My father is very financially conciencious. Think about it yourself. you pay for internet at your home. You have internet access at your office. But if you get a smart phone you're going to pay almost the same amount just for that access. A lot of people take it as just another fixed cost... I'm one of those. I don't even think about it, as I check my facebook from the bus, train, or even while sitting in traffic... The convience of having connection everywhere outweigh the financial responsible person screaming at in the back of my mind. However This conversation lead us to another venue of discussion.... what happens when the power dies. if you left your charger at home, or you phone or navi just stops working... are you going to be able to continue on as you did when it was working... let take the navi as an example... if your navi stops working, how many of you know how to use a map, and navigate? can you even find where you are on a map using the cross streets that your stopped at? This is a skill that unfortunatelly is overlooked these days in the child rearing process. Most people don't see the value, while some others can't do it themselves, so how can they teach their offspring? Take another example.... what if your phone gets lost... or stolen, or you drive over it? do you have the numbers in their memorized? are they recorded somewhere? I know that if it weren't for google sync I wouldn't have them backed up... not sufficiently. And what good does that do if you're in timbuckto and your phone dies, think you can get on the internet to look up those numbers? Don't get me wrong. I'm the first to see the value in technology, and am willing to pay the price to not have to wait for prices to come down. I will pay extra to have that newest thing right now. but let me tell you what.... I know that should I ever procreate it will be a requirement for my offspring (children) to learn how to do something manually before I'll let them use technology. Food for thought?? Let everyone else know what you think.... just sayin'

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• Designing status management for a file processing module

  - by bot

  The background One of the functionality of a product that I am currently working on is to process a set of compressed files ( containing XML files ) that will be made available at a fixed location periodically (local or remote location - doesn't really matter for now) and dump the contents of each XML file in a database. I have taken care of the design for a generic parsing module that should be able to accommodate the parsing of any file type as I have explained in my question linked below. There is no need to take a look at the following link to answer my question but it would definitely provide a better context to the problem Generic file parser design in Java using the Strategy pattern The Goal I want to be able to keep a track of the status of each XML file and the status of each compressed file containing the XML files. I can probably have different statuses defined for the XML files such as NEW, PROCESSING, LOADING, COMPLETE or FAILED. I can derive the status of a compressed file based on the status of the XML files within the compressed file. e.g status of the compressed file is COMPLETE if no XML file inside the compressed file is in a FAILED state or status of the compressed file is FAILED if the status of at-least one XML file inside the compressed file is FAILED. A possible solution The Model I need to maintain the status of each XML file and the compressed file. I will have to define some POJOs for holding the information about an XML file as shown below. Note that there is no need to store the status of a compressed file as the status of a compressed file can be derived from the status of its XML files. public class FileInformation { private String compressedFileName; private String xmlFileName; private long lastModifiedDate; private int status; public FileInformation(final String compressedFileName, final String xmlFileName, final long lastModified, final int status) { this.compressedFileName = compressedFileName; this.xmlFileName = xmlFileName; this.lastModifiedDate = lastModified; this.status = status; } } I can then have a class called StatusManager that aggregates a Map of FileInformation instances and provides me the status of a given file at any given time in the lifetime of the appliciation as shown below : public class StatusManager { private Map<String,FileInformation> processingMap = new HashMap<String,FileInformation>(); public void add(FileInformation fileInformation) { fileInformation.setStatus(0); // 0 will indicates that the file is in NEW state. 1 will indicate that the file is in process and so on.. processingMap.put(fileInformation.getXmlFileName(),fileInformation); } public void update(String filename,int status) { FileInformation fileInformation = processingMap.get(filename); fileInformation.setStatus(status); } } That takes care of the model for the sake of explanation. So whats my question? Edited after comments from Loki and answer from Eric : - I would like to know if there are any existing design patterns that I can refer to while coming up with a design. I would also like to know how I should go about designing the status management classes. I am more interested in understanding how I can model the status management classes. I am not interested in how other components are going to be updated about a change in status at the moment as suggested by Eric.

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• NHibernate and Stored Procedures in C#

  - by Jess Nickson

  I was recently trying and failing to set up NHibernate (v1.2) in an ASP.NET project. The aim was to execute a stored procedure and return the results, but it took several iterations for me to end up with a working solution. In this post I am simply trying to put the required code in one place, in the hope that the snippets may be useful in guiding someone else through the same process. As it is kind’ve the first time I have had to play with NHibernate, there is a good chance that this solution is sub-optimal and, as such, I am open to suggestions on how it could be improved! There are four code snippets that I required: The stored procedure that I wanted to execute The C# class representation of the results of the procedure The XML mapping file that allows NHibernate to map from C# to the procedure and back again The C# code used to run the stored procedure The Stored Procedure The procedure was designed to take a UserId and, from this, go and grab some profile data for that user. Simple, right? We just need to do a join first, because the user’s site ID (the one we have access to) is not the same as the user’s forum ID. CREATE PROCEDURE [dbo].[GetForumProfileDetails] ( @userId INT ) AS BEGIN SELECT Users.UserID, forumUsers.Twitter, forumUsers.Facebook, forumUsers.GooglePlus, forumUsers.LinkedIn, forumUsers.PublicEmailAddress FROM Users INNER JOIN Forum_Users forumUsers ON forumUsers.UserSiteID = Users.UserID WHERE Users.UserID = @userId END I’d like to make a shout out to Format SQL for its help with, well, formatting the above SQL!   The C# Class This is just the class representation of the results we expect to get from the stored procedure. NHibernate requires a virtual property for each column of data, and these properties must be called the same as the column headers. You will also need to ensure that there is a public or protected parameterless constructor. public class ForumProfile : IForumProfile { public virtual int UserID { get; set; } public virtual string Twitter { get; set; } public virtual string Facebook { get; set; } public virtual string GooglePlus { get; set; } public virtual string LinkedIn { get; set; } public virtual string PublicEmailAddress { get; set; } public ForumProfile() { } }   The NHibernate Mapping File This is the XML I wrote in order to make NHibernate a) aware of the stored procedure, and b) aware of the expected results of the procedure. <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="[namespace]" assembly="[assembly]"> <sql-query name="GetForumProfileDetails"> <return-scalar column="UserID" type="Int32"/> <return-scalar column="Twitter" type="String"/> <return-scalar column="Facebook" type="String"/> <return-scalar column="GooglePlus" type="String"/> <return-scalar column="LinkedIn" type="String"/> <return-scalar column="PublicEmailAddress" type="String"/> exec GetForumProfileDetails :UserID </sql-query> </hibernate-mapping>   Calling the Stored Procedure Finally, to bring it all together, the C# code that I used in order to execute the stored procedure! public IForumProfile GetForumUserProfile(IUser user) { return NHibernateHelper .GetCurrentSession() .GetNamedQuery("GetForumProfileDetails") .SetInt32("UserID", user.UserID) .SetResultTransformer( Transformers.AliasToBean(typeof (ForumProfile))) .UniqueResult<ForumProfile>(); } There are a number of ‘Set’ methods (i.e. SetInt32) that allow you specify values for any parameters in the procedure. The AliasToBean method is then required to map the returned scalars (as specified in the XML) to the correct C# class.

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• Doubts about several best practices for rest api + service layer

  - by TheBeefMightBeTough

  I'm going to be starting a project soon that exposes a restful api for business intelligence. It may not be limited to a restful api, so I plan to delegate requests to a service layer that then coordinates multiple domain objects (each of which have business logic local to the object). The api will likely have many calls as it is a long-term project. While thinking about the design, I recalled a few best practices. 1) Use command objects at the controller layer (I'm using Spring MVC). 2) Use DTOs at the service layer. 3) Validate in both the controller and service layer, though for different reasons. I have my doubts about these recommendations. 1) Using command objects adds a lot of extra single-purpose classes (potentially one per request). What exactly is the benefit? Annotation based validation can be done using this approach, sure. What if I have two requests that take the same parameters, but have different validation requirements? I would have to have two different classes with exactly the same members but different annotations? Bleh. 2) I have heard that using DTOs is preferable to parameters because it makes for more maintainable code down the road (say, e.g., requirements change and the service parameters need to be altered). I don't quite understand this. Shouldn't an api be more-or-less set in stone? I would understand that in the early phases of a project (or, especially, an entire company) the domain itself will not be well understood, and thus core domain objects may change along with the apis that manipulate these objects. At this point however the number of api methods should be small and their dependents few, so changes to the methods could easily be tolerated from a maintainability standpoint. In a large api with many methods and a substantial domain model, I would think having a DTO for potentially each domain object would become unwieldy. Am I misunderstanding something here? 3) I see validation in the controller and service layer as redundant in most cases. Why would I validate that parameters are not null and are in general well formed in the controller if the service is going to do exactly the same (and more). Couldn't I just do all the validation in the service and throw a runtime exception with a list of bad parameters then catch that in the controller to make the error messages more presentable? Better yet, couldn't I just make the error messages user-friendly in the service and let the exception trickle up to a global handler (ControllerAdvice in spring, for example)? Is there something wrong with either of these approaches? (I do see a use case for controller validation if the input does not map one-to-one with the service input, but since the controllers are for a rest api and not forms, the api parameters will probably map directly to service parameters.) I do also have a question about unchecked vs checked exceptions. Namely, I'm not really sure why I'd ever want to use a checked exception. Every time I have seen them used they just get wrapped into general exceptions (DomainException, SystemException, ApplicationException, w/e) to reduce the signature length of methods, or devs catch Exception rather than dealing with the App1Exception, App2Exception, Sys1Exception, Sys2Exception. I don't see how either of these practices is very useful. Why not just use unchecked exceptions always and catch the ones you actually do care about? You could just document what unchecked exceptions the method throws.

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• I am trying to figure out the best way to understand how to cache domain objects

  - by Brett Ryan

  I've always done this wrong, I'm sure a lot of others have too, hold a reference via a map and write through to DB etc.. I need to do this right, and I just don't know how to go about it. I know how I want my objects to be cached but not sure on how to achieve it. What complicates things is that I need to do this for a legacy system where the DB can change without notice to my application. So in the context of a web application, let's say I have a WidgetService which has several methods: Widget getWidget(); Collection<Widget> getAllWidgets(); Collection<Widget> getWidgetsByCategory(String categoryCode); Collection<Widget> getWidgetsByContainer(Integer parentContainer); Collection<Widget> getWidgetsByStatus(String status); Given this, I could decide to cache by method signature, i.e. getWidgetsByCategory("AA") would have a single cache entry, or I could cache widgets individually, which would be difficult I believe; OR, a call to any method would then first cache ALL widgets with a call to getAllWidgets() but getAllWidgets() would produce caches that match all the keys for the other method invocations. For example, take the following untested theoretical code. Collection<Widget> getAllWidgets() { Entity entity = cache.get("ALL_WIDGETS"); Collection<Widget> res; if (entity == null) { res = loadCache(); } else { res = (Collection<Widget>) entity.getValue(); } return res } Collection<Widget> loadCache() { // Get widgets from underlying DB Collection<Widget> res = db.getAllWidgets(); cache.put("ALL_WIDGETS", res); Map<String, List<Widget>> byCat = new HashMap<>(); for (Widget w : res) { // cache by different types of method calls, i.e. by category if (!byCat.containsKey(widget.getCategory()) { byCat.put(widget.getCategory(), new ArrayList<Widget>); } byCat.get(widget.getCatgory(), widget); } cacheCategories(byCat); return res; } Collection<Widget> getWidgetsByCategory(String categoryCode) { CategoryCacheKey key = new CategoryCacheKey(categoryCode); Entity ent = cache.get(key); if (entity == null) { loadCache(); } ent = cache.get(key); return ent == null ? Collections.emptyList() : (Collection<Widget>)ent.getValue(); } NOTE: I have not worked with a cache manager, the above code illustrates cache as some object that may hold caches by key/value pairs, though it's not modelled on any specific implementation. Using this I have the benefit of being able to cache all objects in the different ways they will be called with only single objects on the heap, whereas if I were to cache the method call invocation via say Spring It would (I believe) cache multiple copies of the objects. I really wish to try and understand the best ways to cache domain objects before I go down the wrong path and make it harder for myself later. I have read the documentation on the Ehcache website and found various articles of interest, but nothing to give a good solid technique. Since I'm working with an ERP system, some DB calls are very complicated, not that the DB is slow, but the business representation of the domain objects makes it very clumsy, coupled with the fact that there are actually 11 different DB's where information can be contained that this application is consolidating in a single view, this makes caching quite important.

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• How can a developer realize the full value of his work [closed]

  - by Jubbat

  I, honestly, don't want to work as a developer in a company anymore after all I have seen. I want to continue developing software, yes, but not in the way I see it all around me. And I'm in London, a city that congregates lots of great developers from the whole world, so it shouldn't be a problem of location. So, what are my concerns? First of all, best case scenario: you are paying managers salary out of yours. You are consistently underpaid by making up for the average manager negative net return plus his whole salary. Typical scenario. I am a reasonably good developer with common sense who cares for readable code with attention to basic principles. I have found way too often, overconfident and arrogant developers with a severe lack of common sense. Personally, I don't want to follow TDD or Agile practices like all the cool kids nowadays. I would read about them, form my own opinion and take what I feel is useful, but don't follow it sheepishly. I want to work with people who understand that you have to design good interfaces, you absolutely have to document your code, that readability is at the top of your priorities. Also people who don't have a cargo cult mentality too. For instance, the same person who asked me about design patterns in a job interview, later told me that something like a List of Map of Vector of Map of Set (in Java) is very readable. Why would someone ask me about design patterns if they can't even grasp encapsulation? These kind of things are the norm. I've seen many examples. I've seen worse than that too, from very well paid senior devs, by the way. Every second that you spend working with people with such lack of common sense and clear thinking, you are effectively losing money by being terribly inefficient with your time. Yet, with all these inefficiencies, the average developer earns a high salary. So I tried working on my own then, although I don't like the idea. I prefer healthy exchange of opinions and ideas and task division. I then did a bit of online freelancing for a while but I think working in a sweatshop might be more enjoyable. Also, I studied computer engineering and you are in an environment in which your client will presume you don't have any formal education because there is no way to prove it. Again, you are undervalued. You could try building a product, yes. But, of course, luck is a big factor. I wonder if there is a way to work in something you can do well, software development, and be valued for the quality of your work and be paid accordingly, and where you and only you get fairly paid for the value you generate. I know that what I have written seems somehow unlikely but I strongly feel this way. Hopefully someone will understand me and has already figured this out. I don't think I'm alone in this kind of feeling.

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• Omni-directional light shadow mapping with cubemaps in WebGL

  - by Winged

  First of all I must say, that I have read a lot of posts describing an usage of cubemaps, but I'm still confused about how to use them. My goal is to achieve a simple omni-directional (point) light type shading in my WebGL application. I know that there is a lot more techniques (like using Two-Hemispheres or Camera Space Shadow Mapping) which are way more efficient, but for an educational purpose cubemaps are my primary goal. Till now, I have adapted a simple shadow mapping which works with spotlights (with one exception: I don't know how to cut off the glitchy part beyond the reach of a single shadow map texture): glitchy shadow mapping<<< So for now, this is how I understand the usage of cubemaps in shadow mapping: Setup a framebuffer (in case of cubemaps - 6 framebuffers; 6 instead of 1 because every usage of framebufferTexture2D slows down an execution which is nicely described here <<<) and a texture cubemap. Also in WebGL depth components are not well supported, so I need to render it to RGBA first. this.texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_CUBE_MAP, this.texture); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, gl.LINEAR); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, gl.LINEAR); for (var face = 0; face < 6; face++) gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, gl.RGBA, this.size, this.size, 0, gl.RGBA, gl.UNSIGNED_BYTE, null); gl.bindTexture(gl.TEXTURE_CUBE_MAP, null); this.framebuffer = []; for (face = 0; face < 6; face++) { this.framebuffer[face] = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, this.framebuffer[face]); gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, this.texture, 0); gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, this.depthbuffer); var e = gl.checkFramebufferStatus(gl.FRAMEBUFFER); // Check for errors if (e !== gl.FRAMEBUFFER_COMPLETE) throw "Cubemap framebuffer object is incomplete: " + e.toString(); } Setup the light and the camera (I'm not sure if should I store all of 6 view matrices and send them to shaders later, or is there a way to do it with just one view matrix). Render the scene 6 times from the light's position, each time in another direction (X, -X, Y, -Y, Z, -Z) for (var face = 0; face < 6; face++) { gl.bindFramebuffer(gl.FRAMEBUFFER, shadow.buffer.framebuffer[face]); gl.viewport(0, 0, shadow.buffer.size, shadow.buffer.size); gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); camera.lookAt( light.position.add( cubeMapDirections[face] ) ); scene.draw(shadow.program); } In a second pass, calculate the projection a a current vertex using light's projection and view matrix. Now I don't know If should I calculate 6 of them, because of 6 faces of a cubemap. ScaleMatrix pushes the projected vertex into the 0.0 - 1.0 region. vDepthPosition = ScaleMatrix * uPMatrixFromLight * uVMatrixFromLight * vWorldVertex; In a fragment shader calculate the distance between the current vertex and the light position and check if it's deeper then the depth information read from earlier rendered shadow map. I know how to do it with a 2D Texture, but I have no idea how should I use cubemap texture here. I have read that texture lookups into cubemaps are performed by a normal vector instead of a UV coordinate. What vector should I use? Just a normalized vector pointing to the current vertex? For now, my code for this part looks like this (not working yet): float shadow = 1.0; vec3 depth = vDepthPosition.xyz / vDepthPosition.w; depth.z = length(vWorldVertex.xyz - uLightPosition) * linearDepthConstant; float shadowDepth = unpack(textureCube(uDepthMapSampler, vWorldVertex.xyz)); if (depth.z > shadowDepth) shadow = 0.5; Could you give me some hints or examples (preferably in WebGL code) how I should build it?

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