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• load-causing processes disappearing from "top" ps -o pcpu shows bogus numbers

  - by Alec Matusis

  I administer a large number of servers, and I have this problem only with Ubuntu 10.04 LTS: I run a server under normal load (say load average 3.0 on an 8-core server). The "top" command shows processes taking certain % of CPU that cause this load average: say PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 11008 mysql 20 0 25.9g 22g 5496 S 67 76.0 643539:38 mysqld ps -o pcpu,pid -p11008 %CPU PID 53.1 11008 , everything is consistent. The all of the sudden, the process causing the load average disappears from "top", but the process continues to run normally (albeit with a slight performance decrease), and the system load average becomes somewhat higher. The output of ps -o pcpu becomes bogus: # ps -o pcpu,pid -p11008 %CPU PID 317910278 1587 This happened to at least 5 different severs (different brand new IBM System X hardware), each running different software: one httpd 2.2, one mysqld 5.1, and one Twisted Python TCP servers. Each time the kernel was between 2.6.32-32-server and 2.6.32-40-server. I updated some machines to 2.6.32-41-server, and it has not happened on those yet, but the bug is rare (once every 60 days or so). This is from an affected machine: top - 10:39:06 up 73 days, 17:57, 3 users, load average: 6.62, 5.60, 5.34 Tasks: 207 total, 2 running, 205 sleeping, 0 stopped, 0 zombie Cpu(s): 11.4%us, 18.0%sy, 0.0%ni, 66.3%id, 4.3%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 74341464k total, 71985004k used, 2356460k free, 236456k buffers Swap: 3906552k total, 328k used, 3906224k free, 24838212k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 805 root 20 0 0 0 0 S 3 0.0 1493:09 fct0-worker 982 root 20 0 0 0 0 S 1 0.0 111:35.05 fioa-data-groom 914 root 20 0 0 0 0 S 0 0.0 884:42.71 fct1-worker 1068 root 20 0 19364 1496 1060 R 0 0.0 0:00.02 top Nothing causing high load is showing on top, but I have two highly loaded mysqld instances on it, that suddenly show crazy %CPU: #ps -o pcpu,pid,cmd -p1587 %CPU PID CMD 317713124 1587 /nail/encap/mysql-5.1.60/libexec/mysqld and #ps -o pcpu,pid,cmd -p1624 %CPU PID CMD 2802 1624 /nail/encap/mysql-5.1.60/libexec/mysqld Here are the numbers from # cat /proc/1587/stat 1587 (mysqld) S 1212 1088 1088 0 -1 4202752 14307313 0 162 0 85773299069 4611685932654088833 0 0 20 0 52 0 3549 27255418880 5483524 18446744073709551615 4194304 11111617 140733749236976 140733749235984 8858659 0 552967 4102 26345 18446744073709551615 0 0 17 5 0 0 0 0 0 the 14th and 15th numbers according to man proc are supposed to be utime %lu Amount of time that this process has been scheduled in user mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). This includes guest time, guest_time (time spent running a virtual CPU, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations. stime %lu Amount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). On a normal server, these numbers are advancing, every time I check the /proc/PID/stat. On a buggy server, these numbers are stuck at a ridiculously high value like 4611685932654088833, and it's not changing. Has anyone encountered this bug?

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• serving mp3s to mobile devices is flooding nginx with partial requests

  - by drumfire

  I am serving mp3s with a minimalistic nginx server. What I see in my log files is that there are a lot of requests, in particular from AppleCoreMedia and sometimes Android useragents, that flood the server with short requests. Sometimes they keep requesting to download the same partial content for a very long time; sometimes more than an hour. For example: "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" [...] I also get a lot, but not as much, of these: "-" 400 0 "-" "-" 400 0 "-" The IP addresses are always from clients that start downloading shortly after that request, usually they have roughly the same UserAgent as in the first example. emphasized text I have enabled server throttling and connection limits in nginx to limit the huge amount of log entries from equivalent IPs at least somewhat. There was a performance issue when I saw the same behaviour on the previous server that used Apache. I installed nginx on a better server then moved the site. When Apache could not handle more connections from the increasing number of clients effectively that server was ddossed. There was no bandwidth issue with already connected clients and I don't know if the already connected clients were using more than one connection at a time. Please tell me: Are clients that appear to get stuck on a download a Bad Thing™ I heard people say their mobile bandwidth use was much higher than they could account for. I'm thinking this type of client behaviour can account for that. And costs us more bandwidth too. Which up to date alternatives exist out there that can handle serving this type of data better than plain HTTP? Useful general insights for someone who just came into this field straight out of the late 90s. :-)

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• Adaptec 5805 not recognized after reboot

  - by Rakedko ShotGuns

  After rebooting the system, the controller is not recognized. It only works if the computer is shut down and turned off. I have recently updated the firmware to "Adaptec RAID 5805 Firmware Build 18948". How do I fix the problem? Configuration summary --------------------------- 1. Server name.....................raid_test Adaptec Storage Manager agent...7.31.00 (18856) Adaptec Storage Manager console.7.31.00 (18856) Number of controllers...........1 Operating system................Windows Configuration information for controller 1 ------------------------------------------------------- Type............................Controller Model...........................Adaptec 5805 Controller number...............1 Physical slot...................2 Installed memory size...........512 MB Serial number...................8C4510C6C9E Boot ROM........................5.2-0 (18948) Firmware........................5.2-0 (18948) Device driver...................5.2-0 (16119) Controller status...............Optimal Battery status..................Charging Battery temperature.............Normal Battery charge amount (%).......37 Estimated charge remaining......0 days, 16 hours, 12 minutes Background consistency check....Disabled Copy back.......................Disabled Controller temperature..........Normal (40C / 104F) Default logical drive task priority High Performance mode................Dynamic Number of logical devices.......1 Number of hot-spare drives......0 Number of ready drives..........0 Number of drive(s) assigned to MaxCache cache0 Maximum drives allowed for MaxCache cache8 MaxCache Read Cache Pool Size...0 GB NCQ status......................Enabled Stay awake status...............Disabled Internal drive spinup limit.....0 External drive spinup limit.....0 Phy 0...........................No device attached Phy 1...........................No device attached Phy 2...........................No device attached Phy 3...........................1.50 Gb/s Phy 4...........................No device attached Phy 5...........................No device attached Phy 6...........................No device attached Phy 7...........................No device attached Statistics version..............2.0 SSD Cache size..................0 Pages on fetch list.............0 Fetch list candidates...........0 Candidate replacements..........0 69319...........................31293 Logical device..................0 Logical device name............. RAID level......................Simple volume Data space......................148,916 GB Date created....................09/19/2012 Interface type..................Serial ATA State...........................Optimal Read-cache mode.................Enabled Preferred MaxCache read cache settingEnabled Actual MaxCache read cache setting Disabled Write-cache mode................Enabled (write-back) Write-cache setting.............Enabled (write-back) Partitioned.....................Yes Protected by hot spare..........No Bootable........................Yes Bad stripes.....................No Power Status....................Disabled Power State.....................Active Reduce RPM timer................Never Power off timer.................Never Verify timer....................Never Segment 0.......................Present: controller 1, connector 0, device 0, S/N 9RX3KZMT Overall host IOs................99075 Overall MB......................4411203 DRAM cache hits.................71929 SSD cache hits..................0 Uncached IOs....................29239 Overall disk failures...........0 DRAM cache full hits............71929 DRAM cache fetch / flush wait...0 DRAM cache hybrid reads.........3476 DRAM cache flushes..............-- Read hits.......................0 Write hits......................0 Valid Pages.....................0 Updates on writes...............0 Invalidations by large writes...0 Invalidations by R/W balance....0 Invalidations by replacement....0 Invalidations by other..........0 Page Fetches....................0 0...............................0 73..............................10822 8...............................3 46138...........................4916 27184...........................15226 20875...........................323 16982...........................1771 1563............................5317 1948............................2969 Serial attached SCSI ----------------------- Type............................Disk drive Vendor..........................Unknown Model...........................ST3160815AS Serial Number...................9RX3KZMT Firmware level..................3.AAD Reported channel................0 Reported SCSI device ID.........0 Interface type..................Serial ATA Size............................149,05 GB Negotiated transfer speed.......1.50 Gb/s State...........................Optimal S.M.A.R.T. error................No Write-cache mode................Write back Hardware errors.................0 Medium errors...................0 Parity errors...................0 Link failures...................0 Aborted commands................0 S.M.A.R.T. warnings.............0 Solid-state disk (non-spinning).false MaxCache cache capable..........false MaxCache cache assigned.........false NCQ status......................Enabled Phy 0...........................1.50 Gb/s Power State.....................Full rpm Supported power states..........Full rpm, Powered off 0x01............................113 0x03............................98 0x04............................99 0x05............................100 0x07............................83 0x09............................75 0x0A............................100 0x0C............................99 0xBB............................100 0xBD............................100 0xBE............................61 0xC2............................39 0xC3............................69 0xC5............................100 0xC6............................100 0xC7............................200 0xC8............................100 0xCA............................100 Aborted commands................0 Link failures...................0 Medium errors...................0 Parity errors...................0 Hardware errors.................0 SMART errors....................0 End of the configuration information for controller 1

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• Kernel-mode Authentication: 401 errors when accessing site from remote machines

  - by CJM

  I have several Classic ASP sites that use Integrated Windows Authentication and Kerberos delegation. They work OK on the live servers (recently moved to a Server 2008/IIS7 servers), but do not work fully on my development PC or my development server. The IIS on both machines were configured through an IIS web deployment tool package which was exported from an old machine; the deployment didn't work perfectly, and I had to tinker a bit to get the sites working. When accessing the apps locally on either machine, they work fine; when accessing from another machine, the user is prompted by a username/password dialog, and regardless of what you enter, ultimately it results in a 401 (Unauthorised) error. I've tried comparing the configuration of these machines against similar live servers (that all work fine), and they seem generally comparable (given that none of the live servers are yet on IIS7.5 (Windows 7/Server 2008 R2). These applications run in a common application pool which uses a special domain user as it's identity - this user has similar permissions on the live and development machines. On IIS6 platforms, to enable kerberos delegation, I needed to set up some SPNs for this user, and they are still in place (even though I don't believe they are needed any longer for IIS7+ due to kernel-mode authentication), Furthermore, this account is enabled for Kerberos delegation in Active Directory, as is each machine I am dealing with. I'm considering the possibility that the deployment might have made changes/failed to make changes to the IIS configuration thus causing this problem. Perhaps a complete rebuild (minus another web deployment attempt) would solve the problem, but I'd rather fix (thus understand) the current problem. Any ideas so far? I've just had another attempt at fixing this issue, and I've made some progress, but I don't have a complete fix...yet. I've discovered that if I access the sites via IP address (than via NetBIOS name), I get the same dialog, except that it accepts my credentials and thus the application works - not quite a fix, but a useful step. More interestingly, I discovered that if I disable Kernel-mode authentication (in IIS Manager Website Authentication Advanced Settings), the applications work perfectly. My foggy understanding is that this is effectively working in the pre-IIS7 way. A reasonable short-term solution, but consider the following explicit advice from IIS on this issue: By default, IIS enables kernel-mode authentication, which may improve authentication performance and prevent authentication problems with application pools configured to use a custom identity. As a best practice, do not disable this setting if Kerberos authentication is used in your environment and the application pool is configured to use a custom identity. Clearly, this is not the way my applications should be working. So what is the issue?

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• Why doesn't video run smoothly on my laptop anymore?

  - by andygrunt

  This might be an impossible question to answer remotely but I figure there may be some common causes that people can suggest so I think it's worth asking... Video no longer plays smoothly on my laptop. It used to but not for a while now. For example, playing a video on YouTube is pretty typical: I press play (making sure it's not on HD or even HQ) and the video buffers a little then starts to play. At first it plays fine then the video starts to stutter, turning into a slideshow while the sound continues to play smoothly. If I try playing the same video on my Playstation 3 (which is linked to the same network) it plays smoothly so it can't be the connection. Another example is streaming DivX videos. Again, I wait while it buffers and it starts but very soon, instead of a slideshow, this time the video just plays slowly while the sound continues as normal (instantly getting out of sync). Even if I let the video fully load before pressing play (i.e. it's no longer streaming), it still behaves the same way. I can even let it load 100% then save the file to hard disk and use VLC player to view it, and the same thing happens. I'm using an old laptop running Windows XP. For the past several years it's been connected to the router via Wi-Fi but in the past few days I've changed that to a network cable (like my PS3) but that hasn't helped. Yes, I regularly install various bits and pieces of software but nothing that I can identify as being the cause. So, are there known causes of this sort of behaviour and if so, what can I do to fix it? Thanks. Update to answer a few questions... Laptop Spec' (note: video has played back fine for the majority of time I've had the laptop) Toshiba Satellite 1900-603 (possibly called something else outside the UK) Intel Pentium 4 2.2 Ghz Processor Originally had 512Mb memory but recently doubled that to 1 Gig of memory Graphics: ATI Mobility Radeon 16Mb DDR VRAM Windows XP SP3 (Home edition) Over the years I've done several things to speed it up (disabling indexing etc) and am generally happy with the performance. I also regularly have a clear out of old software (if for no other reason than the laptop only has a 40Gb hard disk) and use CCleaner and Glary Utilities to strip out much of the crap from my system. Also recently (after doubling the memory), I've tried a few new things which might be likely candidates for slowing the video down such as Rocketdock, Jingle keyboard (which gives an old style 'clacky' typewriter sound when I type - love it), SugarSync, Taskbar Shuffle. However, the video doesn't play smoothly even when I try quit all these apps.

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• Radeon HD4850 serious issues when using DirectX 10

  - by ricsmania

  Hello, I have a problem with my video card. Whenever I run a DirectX 10 game, it works for a few seconds (10 or so) and then starts displaying nothing but big polygons. I have tested this with Crysis and Resident Evil 5, both have the same problems. The same games running under DirectX 9 work fine, except for some small black squares once in a while. I have the following specs: Asus P7P55D LE Intel Core i5 750 Sapphire Radeon HD4850 1GB 2x2GB Patriot Viper II Sector 5, DDR3 1600 MHz OCZ Stealth X Stream 500SXS 500W At first I thought it could be the video card overheating (it has stock cooling), but the game crashes even when it's running at 50 degrees C, and it's never been higher than 70. I also thought it could be the PSU, but as far as I know 500W is enough for this computer, especially because I haven't overclocked anything. My OS is Windows 7 X64 and I am using Catalyst 10.10, but I have also tried many older versions with no success. I don't think there is a problem with the card itself, or else it wouldn't run DirectX 9 games I believe. I have spent many hours searching for a solution but I couldn't, so any help is appreciated. Thank you. EDIT: I did some further investigation about the problem, and it seems taspeotis was right, it might be related to memory. I slightly underclocked the memory from 993 to 965 MHz and the problem went away completely. Both the black squares using DirectX 9 and the weird polygons using DirectX 10. I was using RE DirectX 10 Benchmark, as it consistently crashed around the same point, and now I can play the full benchmark with no artifacts at all. Unfortunately, the underclock has an obvious hit in performance. Although it's not critical, it's definitely noticeable. So, if the video memory test software showed no erros, but the card needs an underclock to work, what might be the problem? Temperature? Voltage? By the way, I couldn't find what the default voltage for this card is. And what is a good software to try and increase it? I tried Ati Tray Tools but it has a bug that increases the clock speed dramatically whenever I change something in the Overclock tab, so I'm afraid it might fry my card. Worst case scenario, if I don't find I solution I will try to slightly increase the GPU clock to compensate for the memory clock. Thank you again.

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• Vista stuck at "Shutting down..." screen. Any way to get verbose logging?

  - by CapBBeard

  Hi all, My home machine has been running fine for about 3 years, no problems at all. Within the last couple of weeks it's had real trouble trying to shut down. It'll get so far and then just sit there at the "Shutting down..." screen for hours. I've left it overnight, I've tried in safe mode, all to no avail. These days, I just wait for the disk activity to finish up and then hold the power button to turn it off. Feels dirty as, especially because there's a RAID involved! The hardware itself is in pretty good shape and of decent spec; Core 2 Quad, 4GB RAM, 1TB RAID 1+0, so it's not quite like a 7 year old PC coming to end of life! In the last month, hardware hasn't changed except for a new monitor. Admittedly I haven't tried unplugging the monitor but I've never heard of that preventing a shutdown. I might give it a whirl later I guess, as a last resort. I've uninstalled old apps, done updates, checked the event log, looked in device manager, uninstalled all non-present devices, disabled various non-critical devices (imaging, audio etc), unplugged peripherals, stopped non-essential services, unplugged the network, disabled the network adapter entirely, ran chkdsk, verified my RAID, the list goes on. But not a single lead. I'm pretty stumped. It could be hardware, but I have no other evidence to suggest so; when the PC is running, it runs fine. Temperatures are good, gaming is smooth as always, disk performance is fine. Event log even makes it look like the shutdown was completed (gets to the point where the event log service stops). In fact, the PC doesn't appear to realise that I cut the power to it. So my question is, does anyone know if there is a way I can get some verbose output (or a log) from shutdown to give me some idea of what is causing the issue? I'm guessing it's stuck unloading some app/driver but it would be good to get some specifics! Unless anyone has any other ideas? I suspect a reinstall would resolve the issue, however I'm looking to get a new PC built in the next month or so, and the reinstall is going to be quite a big job so I'd rather just wait until then if it comes to that. Would still be nice to get this sorted in the mean time though. Cheers!

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• How to rate-limit concurrent sessions with nginx or haproxy?

  - by bantic

  I'm currently using nginx to reverse-proxy requests from web clients that are doing long-polling to an upstream. Since we're doing long polling (as opposed to websockets), when a client connects it will make multiple http connections to the server in serial, re-establishing a connection every time the server sends it some data (or timing out and re-establishing if the server has nothing to say for 10 seconds). What I'd like to do is limit the number of concurrent web clients. Since the clients are constantly making new HTTP requests instead of keeping a single request open, it's a little tricky to count the total number of web clients (because it's not the same as total number of concurrently connected http clients). The method I've come up with is to track http requests by the originating IP address, and store the IP address somewhere with a TTL of 20 seconds. If a request comes in whose IP isn't recognized, then we check the total number of unexpired stored IP addresses; if that's less than the maximum then we allow this request through. And if a request comes in with an IP address that we can find in the look-up table that hasn't yet expired, then it is allowed through as well. All requests that are allowed through have their IPs added to the table (if not there before) and the TTL refreshed to 20 seconds again. I had actually whipped something together that worked correctly this way using nginx along with the Redis 2.0 Nginx Module (and the nginx lua module to simplify the conditional branching), using redis to store my IP addresses with a TTL (the SETEX command), and checking the table size with the DBSIZE command. This worked but the performance was horrible. nginx and redis ended up using lots of cpu and the machine could only handle a very small number of concurrent requests. The new stick-table and tracking counters that were added to Haproxy in version 1.5 (via a commission from serverfault) seem like they might be ideal to implement exactly this sort of rate limiting, because the stick-table can track IP addresses and automatically expire entries. However, I don't see an easy way to get a total count of the unexpired entries in the stick table, which would be necessary to know the number of connected web clients. I'm curious if anyone has any suggestions, for nginx or haproxy or even for something else not mentioned here that I haven't thought of yet.

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• What the best way to achieve RPO of zero and lowest possible RTO (less than 15 minutes) with SQL 2008 R2?

  - by Adrian Hope-Bailie

  We are running a payments (EFT transaction processing) application which is processing high volumes of transactions 24/7 and are currently investigating a better way of doing DB replication to our disaster recovery site. Our current and previous strategies have included using both DoubleTake and Redgate to replicate data to a warm stand-by. DoubleTake is the supported solution from the payments software vendor however their (DoubleTake's) support in South Africa is very poor. We had a few issues and simply couldn't ever resolve them so we had to give up on DoubleTake. We have been using Redgate to manually read the data from the primary site (via queries) and write to the DR site but this is: A bad solution Getting the software vendor hot and bothered whenever we have support issues as it has a tendency to interfere with the payment application which is very DB intensive. We recently upgraded the whole system to run on SQL 2008 R2 Enterprise which means we should probably be looking at using some of the built-in replication features. The server has 2 fairly large databases with a mixture of tables containing highly volatile transactional data and pretty static configuration data. Replication would be done over a WAN link to a separate physical site and needs to achieve the following objectives. RPO: Zero loss - This is transactional data with financial impact so we can't lose anything. RTO: Tending to zero - The business depends on our ability to process transactions every minute we are down we are losing money I have looked at a few of the other questions/answers but none meet our case exactly: SQL Server 2008 failover strategy - Log shipping or replication? How to achieve the following RTO & RPO with logshipping only using SQL Server? What is the best of two approaches to achieve DB Replication? My current thinking is that we should use mirroring but I am concerned that for RPO:0 we will need to do delayed commits and this could impact the performance of the primary DB which is not an option. Our current DR process is to: Stop incoming traffic to the primary site and allow all in-flight transaction to complete. Allow the replication to DR to complete. Change network routing to route to DR site. Start all applications and services on the secondary site (Ideally we can change this to a warmer stand-by whereby the applications are already running but not processing any transactions). In other words the DR database needs to, as quickly as possible, catch up with primary and be ready for processing as the new primary. We would then need to be able to reverse this when we are ready to switch back. Is there a better option than mirroring (should we be doing log-shipping too) and can anyone suggest other considerations that we should keep in mind?

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• Synchronize the same set of files to 2 different locations with 2 different programs for 2 different purposes

  - by Hedgetrimmer

  Because of stupid questionable IT policies at my not-to-be-named place of occupation, I have been (and will be, for the forseeable future) carrying on an external hard drive a unison-synchronized copy of all of my documents and code, including code which resides in some of my "dotfiles" and other code which resides in ~/bin (things I've made are there because ~/bin is in my $PATH) along with some cruft generated (and to be generated) by conscript and its related "giter8" templating system for Scala project boilerplates. Despite this, I do use a symlinking program to store all of my important dotfiles in a subdirectory. Thanks to that somewhat complicated setup, I have resorted to making a directory full of symlinks to every directory (or file, as is the case with stuff under ~/bin) that I want synchronized, and then follow = True is in my unison profile. It happens to be that this collection of odds and ends—plus an automatically-generated text file containing every package installed on my system—is everything under ~ that needs to be backed up to a remote (rsync-over-ssh) host with client-side encryption and signing from GPG. I already believe that duplicity is the most appropriate program to do that. What isn't as clear-cut is how to make duplicity use the exact same set of files when it runs a backup; it would be simple if duplicity would follow symlinks, but it does not and the manpage lists no option for enabling any such behavior. Comparing unison's file selection algorithm to duplicity's, I don't think I can write a program that could compute a ruleset for one program given one for the other. For the record, I would rather not keep the symlinks manually synchronized with duplicity file-selection rules, as they can change thanks to the above-mentioned complications regarding ~/bin. I don't think running duplicity on the external hard disk is such a good idea either; I usually keep that hard disk unmounted and unplugged in case of a power failure or other physical problem with the computer, plus I'm not sure about duplicity's performance given that: the hard disk is NTFS-formatted in order to be useable at my Windows-imprisoned place of occupation. despite being a USB 3.0 disk, my computer has no USB 3.0 ports so it acts as a USB 2.0 disk. How can I have duplicity (or is there a better program that I have overlooked?) back up the exact same set of files that is bidirectionally synchronized with my external hard disk?

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• Is there a Distributed SAN/Storage System out there?

  - by Joel Coel

  Like many other places, we ask our users not to save files to their local machines. Instead, we encourage that they be put on a file server so that others (with appropriate permissions) can use them and that the files are backed up properly. The result of this is that most users have large hard drives that are sitting mainly empty. It's 2010 now. Surely there is a system out there that lets you turn that empty space into a virtual SAN or document library? What I envision is a client program that is pushed out to users' PCs that coordinates with a central server. The server looks to users just like a normal file server, but instead of keeping entire file contents it merely keeps a record of where those files can be found among various user PCs. It then coordinates with the right clients to serve up file requests. The client software would be able to respond to such requests directly, as well as be smart enough to cache recent files locally. For redundancy the server could make sure files are copied to multiple PCs, perhaps allowing you to define groups in different locations so that an instance of the entire repository lives in each group to protect against a disaster in one building taking down everything else. Obviously you wouldn't point your database server here, but for simpler things I see several advantages: Files can often be transferred from a nearer machine. Disk space grows automatically as your company does. Should ultimately be cheaper, as you don't need to keep a separate set of disks I can see a few downsides as well: Occasional degradation of user pc performance, if the machine has to serve or accept a large file transfer during a busy period. Writes have to be propogated around the network several times (though I suspect this isn't really much of a problem, as reading happens in most places more than writing) Still need a way to send a complete copy of the data offsite occasionally, and this would make it very hard to do differentials Think of this like a cloud storage system that lives entirely within your corporate LAN and makes use of your existing user equipment. Our old main file server is due for retirement in about 2 years, and I'm looking into replacing it with a small SAN. I'm thinking something like this would be a better fit. As a school, we have a couple computer labs I can leave running that would be perfect for adding a little extra redundancy to the system. Unfortunately, the closest thing I can find is Dienst, and it's just a paper that dates back to 1994. Am I just using the wrong buzzwords in my searches, or does this really not exist? If not, is there a big downside that I'm missing?

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• Nginx, proxy passing to Apache, and SSL

  - by Vic

  I have Nginx and Apache set up with Nginx proxy-passing everything to Apache except static resources. I have a server set up for port 80 like so: server { listen 80; server_name *.example1.com *.example2.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass http://127.0.0.1:8080; include /etc/nginx/conf.d/proxy.conf; } } And since we have multiple ssl sites (with different ssl certificates) I have a server{} block for each of them like so: server { listen 443 ssl; server_name *.example1.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass https://127.0.0.1:8443; include /etc/nginx/conf.d/proxy.conf; proxy_set_header X-Forwarded-Port 443; proxy_set_header X-Forwarded-Proto https; } } server { listen 443 ssl; server_name *.example2.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass https://127.0.0.1:8445; include /etc/nginx/conf.d/proxy.conf; proxy_set_header X-Forwarded-Port 443; proxy_set_header X-Forwarded-Proto https; } } First of all, I think there is a very obvious problem here, which is that I'm double-encrypting everything, first at the nginx level and then again by Apache. To make everything worse, I just started using Amazon's Elastic Load Balancer, so I added the certificate to the ELB and now SSL encryption is happening three times. That's gotta be horrible for performance. What is the sane way to handle this? Should I be forwarding https on the ELB - http on nginx - http on apache? Secondly, there is so much duplication above. Is the best method to not repeat myself to put all of the static asset handling in an include file and just include it in the server?

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• Add Machine Key to machine.config in Load Balancing environment to multiple versions of .net framework

  - by davidb

  I have two web servers behind a F5 load balancer. Each web server has identical applications to the other. There was no issue until the config of the load balancer changed from source address persistence to least connections. Now in some applications I receieve this error Server Error in '/' Application. Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Source Error: The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL: Add a "Debug=true" directive at the top of the file that generated the error. Example: or: 2) Add the following section to the configuration file of your application: Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode. Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario. How do I add a machine key to the machine.config file? Do I do it at server level in IIS or at website/application level for each site? Does the validation and decryption keys have to be the same across both web servers or are they different? Should they be different for each machine.config version of .net? I cannot find any documentation of this scenario.

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• How to disable or tune filesystem cache sharing for OpenVZ?

  - by gertvdijk

  For OpenVZ, an example of container-based virtualization, it seems that host and all guests are sharing the filesystem cache. This sounds paradoxical when talking about virtualization, but this is actually a feature of OpenVZ. It makes sense too. Because only one kernel is running, it's possible to benefit from sharing the same pages of filesystem cache in memory. And while it sounds beneficial, I think a set up here actually suffers in performance from it. Here's why I think why: my machines aren't actually sharing any files on disk so I can't benefit from this feature in OpenVZ. Several OpenVZ machines are running MySQL with MyISAM tables. MyISAM relies on the system's filesystem cache for caching of data files, unlike InnoDB's buffer pool. Also some virtual machines are known to do heavy and large I/O operations on the same filesystem in the host. For example, when running cat *.MYD > /dev/null on some large database in one machine, I saw the filesystem cache lowering in another, monitored by htop. This essentially flushes all the useful filesystem cache in guests (FIFO) and so it flushes the MySQL caches in the guests. Now users are complaining that MySQL is very slow. And it is. Some simple SELECT queries take several seconds on times disk I/O is heavily used by other machines. So, simply put: Is there a way to avoid filesystem cache being wiped out by other virtual machines in container-based virtualization? Some thoughts: Choosing algorithm for flushing filesystem cache in the kernel. (possible? how?) Reserving a certain amount of pages for a single VM. (seems no option for filesystem cache type of pages that reading man vzctl) Will running MySQL on another filesystem get me anywhere? If not, I think my alternatives are: Use KVM for MySQL-MyISAM running VMs. KVM actually assigns memory to the VM and does not allow swapping out caches unless using a balloon driver. Move to InnoDB and tune the buffer pools, dirty pages, etc. This is now considered to be 'nice to have' on the long-term as not everyone responsible for administration of the system understands InnoDB. more suggestions welcome. System software: Proxmox (now 1.9, could be upgraded to 2.x). One big LV assigned for the VMs.

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• Will spreading your servers load not just consume more recourses

  - by Saif Bechan

  I am running a heavy real-time updating website. The amount of recourses needed per user are quite high, ill give you an example. Setup Every visit The application is php/mysql so on every visit static and dynamic content is loaded. Recourses: apache,php,mysql Every second (no more than a second will just be too long) The website needs to be updated real-time so every second there is an ajax call thats updates the website. Recourses: jQuery,apache,php,mysql Avarage spending for single user (spending one minute and visited 3 pages) Apache: +/- 63 requests / responsess serving static and dynamic content (img,css,js,html) php: +/- 63 requests / responses mysql: +/- 63 requests / responses jquery: +/- 60 requests / responses Optimization I want to optimize this process, but I think that maybe it would be just the same in the end. Before implementing and testing (which will take weeks) I wanted to have some second opinions from you guys. Every visit I want to start off with having nginx in the front and work as a proxy to deliver the static content. Recources: Dynamic: apache,php,mysql Static: nginx This will spread the load on apache a lot. Every Second For the script that loads every second I want to set up Node.js server side javascript with nginx in te front. I want to set it up that jquery makes a request ones a minute, and node.js streams the data to the client every second. Recources: jQuery,nginx,node.js,mysql Avarage spending for single user (spending one minute and visited 3 pages) Nginx: 4 requests / responsess serving mostly static conetent(img,css,js) Apache: 3 requests only the pages php: 3 requests only the pages node.js: 1 request / 60 responses jquery: 1 request / 60 responses mysql: 63 requests / responses Optimization As you can see in the optimisation the load from Apache and PHP are lifted and places on nginx and node.js. These are known for there light footprint and good performance. But I am having my doubts, because there are still 2 programs extra loaded in the memory and they consume cpu. So it it better to have less programs that do the job, or more. Before I am going to spend a lot of time setting this up I would like to know if it will be worth the while.

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• nginx rewrite for /blah/(.*) /$1

  - by skrewler

  I'm migrating from mod_php to nginx. I got everything working except for this rewrite.. I'm just not familiar enough with nginx configuration to know the correct way to do this. I came up with this by looking at a sample on the nginx site. server { server_name test01.www.myhost.com; root /home/vhosts/my_home/blah; access_log /var/log/nginx/blah.access.log; error_log /var/log/nginx/blah.error.log; index index.php; location / { try_files $uri $uri/ @rewrites; } location @rewrites { rewrite ^ /index.php last; rewrite ^/ht/userGreeting.php /js/iFrame/index.php last; rewrite ^/ht/(.*)$ /$1 last; rewrite ^/userGreeting.php$ /js/iFrame/index.php last; rewrite ^/a$ /adminLogin.php last; rewrite ^/boom\/(.*)$ /boom/index.php?q=$1 last; rewrite ^favicon.ico$ favico_ry.ico last; } # This block will catch static file requests, such as images, css, js # The ?: prefix is a 'non-capturing' mark, meaning we do not require # the pattern to be captured into $1 which should help improve performance location ~* \.(?:ico|css|js|gif|jpe?g|png)$ { # Some basic cache-control for static files to be sent to the browser expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; } include php.conf; } The issue I'm having is with this rewrite: rewrite ^ht\/(.*)$ /$1 last; 99% of requests that will hit this rewrite are static files. So I think maybe it's getting sent to the static files section and that's where things are being messed up? I tried adding this but it didn't work: location ~* ^ht\/.*\.(?:ico|css|js|gif|jpe?g|png)$ { # Some basic cache-control for static files to be sent to the browser expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; } Any help would be appreciated. I know the best thing to do would be to just change the references of /ht/whatever.jpg to /whatever.jpg in the code.. but that's not an option for now.

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• MongoDB and datasets that don't fit in RAM no matter how hard you shove

  - by sysadmin1138

  This is very system dependent, but chances are near certain we'll scale past some arbitrary cliff and get into Real Trouble. I'm curious what kind of rules-of-thumb exist for a good RAM to Disk-space ratio. We're planning our next round of systems, and need to make some choices regarding RAM, SSDs, and how much of each the new nodes will get. But now for some performance details! During normal workflow of a single project-run, MongoDB is hit with a very high percentage of writes (70-80%). Once the second stage of the processing pipeline hits, it's extremely high read as it needs to deduplicate records identified in the first half of processing. This is the workflow for which "keep your working set in RAM" is made for, and we're designing around that assumption. The entire dataset is continually hit with random queries from end-user derived sources; though the frequency is irregular, the size is usually pretty small (groups of 10 documents). Since this is user-facing, the replies need to be under the "bored-now" threshold of 3 seconds. This access pattern is much less likely to be in cache, so will be very likely to incur disk hits. A secondary processing workflow is high read of previous processing runs that may be days, weeks, or even months old, and is run infrequently but still needs to be zippy. Up to 100% of the documents in the previous processing run will be accessed. No amount of cache-warming can help with this, I suspect. Finished document sizes vary widely, but the median size is about 8K. The high-read portion of the normal project processing strongly suggests the use of Replicas to help distribute the Read traffic. I have read elsewhere that a 1:10 RAM-GB to HD-GB is a good rule-of-thumb for slow disks, As we are seriously considering using much faster SSDs, I'd like to know if there is a similar rule of thumb for fast disks. I know we're using Mongo in a way where cache-everything really isn't going to fly, which is why I'm looking at ways to engineer a system that can survive such usage. The entire dataset will likely be most of a TB within half a year and keep growing.

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• What DNS server to use for dynamic load-balancing of website?

  - by Marki555

  I will have 2 servers in different datacenters (different countries) and I want to use DNS load-balancing mainly for High Availability of website hosted on those 2 servers. It is just ad tracking site, which records hit in local database and returns few lines on html code. I want to return 2 A records each time because of DNS pinning in browsers (if one server fails, browser will try second A record which it has already cached). Both servers will be acting also as DNS servers for redundancy. Now comes my proposed solution: I will use BIND and have both servers as a master for that zone. On each server there will be running script, which will periodically test availability (http) of both servers and remove IP from DNS in case of failure. Now the questions :) 1) Is BIND suitable for this solution? I think BIND performance is good and it is easy to manipulate the zone file via script. And as I will modify the zone only in case of failure/maintenance, the modifications (and thus bind reload) won't be often. 2) I plan to use TTL of 5 minutes. The website will have about 1000-3000 req/s but from distinct clients (each IP only 1-3 requests), so I think the DNS load won't be too much. I suppose their ISPs will cache the responses for those 5 mins. Is there any reason to lower the TTL even more? 3) Is my master-master approach good? Or should I make one of the servers master and the other one slave? Right now each server can monitor both itself and the other one. If only webservice fails, both DNS nodes will notice it. If the whole server fails, then the remaining DNS node will notice it and the failed node will not answer DNS queries anyway. 4) Is it a big issue when one NS server does not respond to queries? If yes, I can make a third DNS, so anytime at least 2 of them would accept queries... 5) Should I rewrite the zone file via script, or just use dynamic DNS update (for example via nsupdateutility)?

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• Troubleshooting Network Speeds -- The Age Old Inquiry

  - by John K

  I'm looking for help with what I'm sure is an age old question. I've found myself in a situation of yearning to understand network throughput more clearly, but I can't seem to find information that makes it "click" We have a few servers distributed geographically, running various versions of Windows. Assuming we always use one host (a desktop) as the source, when copying data from that host to other servers across the country, we see a high variance in speed. In some cases, we can copy data at 12MB/s consistently, in others, we're seeing 0.8 MB/s. It should be noted, after testing 8 destinations, we always seem to be at either 0.6-0.8MB/s or 11-12 MB/s. In the building we're primarily concerned with, we have an OC-3 connection to our ISP. I know there are a lot of variables at play, but I guess I was hoping the experts here could help answer a few basic questions to help bolster my understanding. 1.) For older machines, running Windows XP, server 2003, etc, with a 100Mbps Ethernet card and 72 ms typical latency, does 0.8 MB/s sound at all reasonable? Or do you think that slow enough to indicate a problem? 2.) The classic "mathematical fastest speed" of "throughput = TCP window / latency," is, in our case, calculated to 0.8 MB/s (64Kb / 72 ms). My understanding is that is an upper bounds; that you would never expect to reach (due to overhead) let alone surpass that speed. In some cases though, we're seeing speeds of 12.3 MB/s. There are Steelhead accelerators scattered around the network, could those account for such a higher transfer rate? 3.) It's been suggested that the use SMB vs. SMB2 could explain the differences in speed. Indeed, as expected, packet captures show both being used depending on the OS versions in play, as we would expect. I understand what determines SMB2 being used or not, but I'm curious to know what kind of performance gain you can expect with SMB2. My problem simply seems to be a lack of experience, and more importantly, perspective, in terms of what are and are not reasonable network speeds. Could anyone help impart come context/perspective?

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• How to prevent dual booted OSes from damaging each other?

  - by user1252434

  For better compatibility and performance in games I'm thinking about installing Windows additionally to Linux. I have security concerns about this, though. Note: "Windows" in the remaining text includes not only the OS but also any software running on it. Regardless of whether it comes included or is additionally installed, whether it is started intentionally or unintentionally (virus, malware). Is there an easy way to achieve the following requirements: Windows MUST NOT be able to kill my linux partition or my data disk neither single files (virus infection) nor overwriting the whole disk Windows MUST NOT be able to read data disk (- extra protection against spyware) Linux may or may not have access to the windows partition both Linux and Windows should have full access to the graphics card this rules out desktop VM solutions for gaming I want the manufacturer's windows graphics card driver Regarding Windows to be unable to destroy my linux install: this is not just the usual paranoia, that has happened to me in the past. So I don't accept "no ext4 driver" as an argument. Once bitten, twice shy. And even if destruction targeted at specific (linux) files is nearly impossible, there should be no way to shred the whole partition. I may accept the risk of malware breaking out of a barrier (e.g. VM) around the whole windows box, though. Currently I have a system disk (SSD) and a data disk (HDD), both SATA. I expect I have to add another disk. If i don't: even better. My CPU is a Intel Core i5, with VT-x and VT-d available, though untested. Ideas I've had so far: deactivate or hide other HDs until reboot at low level possible? can the boot loader (grub) do this for me? tiny VM layer: load windows in a VM that provides access to almost all hardware, except the HDs any ready made software solution for this? Preferably free. as I said: the main problem seems to be to provide full access to the graphics card hardware switch to cut power to disks commercial products expensive and lots of warnings against cheap home built solutions preferably all three hard disks with one switch (one push) mobile racks - won't wear of daily swapping be a problem?

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• What else can I do to secure my Linux server?

  - by eric01

  I want to put a web application on my Linux server: I will first explain to you what the web app will do and then I will tell you what I did so far to secure my brand new Linux system. The app will be a classified ads website (like gumtree.co.uk) where users can sell their items, upload images, send to and receive emails from the admin. It will use SSL for some pages. I will need SSH. So far, what I did to secure my stock Ubuntu (latest version) is the following: NOTE: I probably did some things that will prevent the application from doing all its tasks, so please let me know of that. My machine's sole purpose will be hosting the website. (I put numbers as bullet points so you can refer to them more easily) 1) Firewall I installed Uncomplicated Firewall. Deny IN & OUT by default Rules: Allow IN & OUT: HTTP, IMAP, POP3, SMTP, SSH, UDP port 53 (DNS), UDP port 123 (SNTP), SSL, port 443 (the ones I didn't allow were FTP, NFS, Samba, VNC, CUPS) When I install MySQL & Apache, I will open up Port 3306 IN & OUT. 2) Secure the partition in /etc/fstab, I added the following line at the end: tmpfs /dev/shm tmpfs defaults,rw 0 0 Then in console: mount -o remount /dev/shm 3) Secure the kernel In the file /etc/sysctl.conf, there are a few different filters to uncomment. I didn't know which one was relevant to web app hosting. Which one should I activate? They are the following: A) Turn on Source Address Verification in all interfaces to prevent spoofing attacks B) Uncomment the next line to enable packet forwarding for IPv4 C) Uncomment the next line to enable packet forwarding for IPv6 D) Do no accept ICMP redirects (we are not a router) E) Accept ICMP redirects only for gateways listed in our default gateway list F) Do not send ICMP redirects G) Do not accept IP source route packets (we are not a router) H) Log Martian Packets 4) Configure the passwd file Replace "sh" by "false" for all accounts except user account and root. I also did it for the account called sshd. I am not sure whether it will prevent SSH connection (which I want to use) or if it's something else. 5) Configure the shadow file In the console: passwd -l to lock all accounts except user account. 6) Install rkhunter and chkrootkit 7) Install Bum Disabled those services: "High performance mail server", "unreadable (kerneloops)","unreadable (speech-dispatcher)","Restores DNS" (should this one stay on?) 8) Install Apparmor_profiles 9) Install clamav & freshclam (antivirus and update) What did I do wrong and what should I do more to secure this Linux machine? Thanks a lot in advance

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• WPF DataContext does not refresh the DataGrid using MVVM model

  - by vikram bhatia

  Project Overview I have a view which binds to a viewmodel containing 2 ObserverableCollection. The viewmodel constructor populates the first ObserverableCollection and the view datacontext is collected to bind to it through a public property called Sites. Later the 2ed ObserverableCollection is populated in the LoadOrders method and the public property LoadFraudResults is updated for binding it with datacontext. I am using WCF to pull the data from the database and its getting pulled very nicely. VIEWMODEL SOURCE class ManageFraudOrderViewModel:ViewModelBase { #region Fields private readonly ICollectionView collectionViewSites; private readonly ICollectionView collectionView; private ObservableCollection<GeneralAdminService.Website> _sites; private ObservableCollection<FraudService.OrderQueue> _LoadFraudResults; #endregion #region Properties public ObservableCollection<GeneralAdminService.Website> Sites { get { return this._sites; } } public ObservableCollection<FraudService.OrderQueue> LoadFraudResults { get { return this._LoadFraudResults;} } #endregion public ManageFraudOrderViewModel() { //Get values from wfc service model GeneralAdminService.GeneralAdminServiceClient generalAdminServiceClient = new GeneralAdminServiceClient(); GeneralAdminService.Website[] websites = generalAdminServiceClient.GetWebsites(); //Get values from wfc service model if (websites.Length > 0) { _sites = new ObservableCollection<Wqn.Administration.UI.GeneralAdminService.Website>(); foreach (GeneralAdminService.Website website in websites) { _sites.Add((Wqn.Administration.UI.GeneralAdminService.Website)website); } this.collectionViewSites= CollectionViewSource.GetDefaultView(this._sites); } generalAdminServiceClient.Close(); } public void LoadOrders(Wqn.Administration.UI.FraudService.Website website) { //Get values from wfc service model FraudServiceClient fraudServiceClient = new FraudServiceClient(); FraudService.OrderQueue[] OrderQueue = fraudServiceClient.GetFraudOrders(website); //Get values from wfc service model if (OrderQueue.Length > 0) { _LoadFraudResults = new ObservableCollection<Wqn.Administration.UI.FraudService.OrderQueue>(); foreach (FraudService.OrderQueue orderQueue in OrderQueue) { _LoadFraudResults.Add(orderQueue); } } this.collectionViewSites= CollectionViewSource.GetDefaultView(this._LoadFraudResults); fraudServiceClient.Close(); } } VIEW SOURCE public partial class OrderQueueControl : UserControl { private ManageFraudOrderViewModel manageFraudOrderViewModel ; private OrderQueue orderQueue; private ButtonAction ButtonAction; private DispatcherTimer dispatcherTimer; public OrderQueueControl() { LoadOrderQueueForm(); } #region LoadOrderQueueForm private void LoadOrderQueueForm() { //for binding the first observablecollection manageFraudOrderViewModel = new ManageFraudOrderViewModel(); this.DataContext = manageFraudOrderViewModel; } #endregion private void cmbWebsite_SelectionChanged(object sender, SelectionChangedEventArgs e) { BindItemsSource(); } #region BindItemsSource private void BindItemsSource() { using (OverrideCursor cursor = new OverrideCursor(Cursors.Wait)) { if (!string.IsNullOrEmpty(Convert.ToString(cmbWebsite.SelectedItem))) { Wqn.Administration.UI.FraudService.Website website = (Wqn.Administration.UI.FraudService.Website)Enum.Parse(typeof(Wqn.Administration.UI.FraudService.Website),cmbWebsite.SelectedItem.ToString()); //for binding the second observablecollection******* manageFraudOrderViewModel.LoadOrders(website); this.DataContext = manageFraudOrderViewModel; //for binding the second observablecollection******* } } } #endregion } XAML ComboBox x:Name="cmbWebsite" ItemsSource="{Binding Sites}" Margin="5" Width="100" Height="25" SelectionChanged="cmbWebsite_SelectionChanged" DataGrid ItemsSource ={Binding Path = LoadFraudResults} PROBLEM AREA: When I call the LoadOrderQueueForm to bind the first observablecollection and later BindItemsSource to bind 2ed observable collection, everything works fine and no problem for the first time binding. But, when I call BindItemsSource again to repopulate the obseravablecollection based on changed selected combo value via cmbWebsite_SelectionChanged, the observalblecollection gets populated with new value and LoadFraudResults property in viewmodule is populated with new values; but when i call the datacontext to rebind the datagrid,the datagrid does not reflect the changed values. In other words the datagrid doesnot get changed when the datacontext is called the 2ed time in BindItemsSource method of the view. manageFraudOrderViewModel.LoadOrders(website); this.DataContext = manageFraudOrderViewModel; manageFraudOrderViewModel values are correct but the datagrid is not relected with changed values. Please help as I am stuck with this thing for past 2 days and the deadline is approaching near. Thanks in advance

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• protobuf-net: Issues deserializing DataMember fields in lieu of read-only property

  - by Paul Smith

  I'm having issues deserializing certain properties of ORM-generated entities using protobuf-net. I suspect something in the way the ORM manages serialization attributes on read-only properties (uses public backing fields with DataMember attributes & [de]serializes) those instead of the corresponding read-only property, which has an IgnoreDataMember attribute). Guid properties might have issues of their own, but the field vs. property thing is my working theory now. Here's a simplified example of the code. Say I have a class, Account with an AccountID read-only guid, and an AccountName read-write string. I serialize & immediately deserialize a clone. In this scenario I get one of two results (depending on the entity, haven't isolated the specific commonality yet). The deserialized clone either: ...has a different AccountID from the original, or ...throws an Incorrect wire-type deserializing Guid exception while deserializing. Here's example usage... Account acct = new Account() { AccountName = "Bob's Checking" }; Debug.WriteLine(acct.AccountID.ToString()); using (MemoryStream ms = new MemoryStream()) { ProtoBuf.Serializer.Serialize<Account>(ms, acct); Debug.WriteLine(Encoding.UTF8.GetString(ms.GetBuffer())); ms.Position = 0; Account clone = ProtoBuf.Serializer.Deserialize<Account>(ms); Debug.WriteLine(clone.AccountID.ToString()); } And here's an example ORM'd class (simplified; hopefully haven't removed the cause of the issue in the process). Uses a shell game to deserialize read-only properties by exposing the backing field ("can't write" essentially becomes "shouldn't write," but we can scan code for instances of assigning to these fields, so the hack works for our purposes): [DataContract()] [Serializable()] public partial class Account { public Account() { _accountID = Guid.NewGuid(); } [XmlAttribute("AccountID")] [DataMember(Name = "AccountID", Order = 0)] public Guid _accountID; /// <summary> /// A read-only property; XML, JSON and DataContract serializers all seem /// to correctly recognize the public backing field when deserializing: /// </summary> [IgnoreDataMember] [XmlIgnore] public Guid AccountID { get { return this._accountID; } } [IgnoreDataMember] protected string _accountName; [DataMember(Name = "AccountName", Order = 1)] [XmlAttribute] public string AccountName { get { return this._accountName; } set { this._accountName = value; } } } XML, JSON and DataContract serializers all seem to serialize / deserialize matching object graphs here, so this attribute arrangement apparently causes those serializers to correctly assign to the public backing field when deserializing. I've tried protobuf-net with lists vs. single instances, different prefix styles, etc., but always either get the 'incorrect wire type ... Guid' exception, or the Guid property (field) not deserializing correctly. So the specific questions are, is there a quick workaround for this, and/or is there an explanation for both of outcomes 1 & 2 above, and/or can protobuf-net somehow be corralled into behaving like WCF in cases like this (i.e. follow the same DataMember/IgnoreDataMember semantics)? We hope not to have to create a protobuf dependency directly in the entity layer; if that's the case, we'll probably create proxy DTO entities with all public properties having protobuf attributes. (This is a subjective issue I have with all declarative serialization models; it's a ubiquitous pattern, but IMO, "normal" should be to have objects and serialization contracts decoupled.) Thanks!

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• Refactoring multiple interfaces to a common interface using MVVM, MEF and Silverlight4

  - by Brian

  I am just learning MVVM with MEF and already see the benefits but I am a little confused about some implementation details. The app I am building has several Models that do the same with with different entities (WCF RIA Services exposing a Entity framework object) and I would like to avoid implementing a similar interface/model for each view I need and the following is what I have come up with though it currently doesn't work. The common interface has a new completed event for each model that implements the base model, this was the easiest way I could implement a common class as the compiler did not like casting from a child to the base type. The code as it currently sits compiles and runs but the is a null IModel being passed into the [ImportingConstructor] for the FaqViewModel class. I have a common interface (simplified for posting) defined as follows, this should look familiar to those who have seen Shawn Wildermuth's RIAXboxGames sample. public interface IModel { void GetItemsAsync(); event EventHandler<EntityResultsArgs<faq>> GetFaqsComplete; } A base method that implements the interface public class ModelBase : IModel { public virtual void GetItemsAsync() { } public virtual event EventHandler<EntityResultsArgs<faq>> GetFaqsComplete; protected void PerformQuery<T>(EntityQuery<T> qry, EventHandler<EntityResultsArgs<T>> evt) where T : Entity { Context.Load(qry, r => { if (evt == null) return; try { if (r.HasError) { evt(this, new EntityResultsArgs<T>(r.Error)); } else if (r.Entities.Count() > 0) { evt(this, new EntityResultsArgs<T>(r.Entities)); } } catch (Exception ex) { evt(this, new EntityResultsArgs<T>(ex)); } }, null); } private DomainContext _domainContext; protected DomainContext Context { get { if (_domainContext == null) { _domainContext = new DomainContext(); _domainContext.PropertyChanged += DomainContext_PropertyChanged; } return _domainContext; } } void DomainContext_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { switch (e.PropertyName) { case "IsLoading": AppMessages.IsBusyMessage.Send(_domainContext.IsLoading); break; case "IsSubmitting": AppMessages.IsBusyMessage.Send(_domainContext.IsSubmitting); break; } } } A model that implements the base model [Export(ViewModelTypes.FaqViewModel, typeof(IModel))] public class FaqModel : ModelBase { public override void GetItemsAsync() { PerformQuery(Context.GetFaqsQuery(), GetFaqsComplete); } public override event EventHandler<EntityResultsArgs<faq>> GetFaqsComplete; } A view model [PartCreationPolicy(CreationPolicy.NonShared)] [Export(ViewModelTypes.FaqViewModel)] public class FaqViewModel : MyViewModelBase { private readonly IModel _model; [ImportingConstructor] public FaqViewModel(IModel model) { _model = model; _model.GetFaqsComplete += Model_GetFaqsComplete; _model.GetItemsAsync(); // Load FAQS on creation } private IEnumerable<faq> _faqs; public IEnumerable<faq> Faqs { get { return _faqs; } private set { if (value == _faqs) return; _faqs = value; RaisePropertyChanged("Faqs"); } } private faq _currentFaq; public faq CurrentFaq { get { return _currentFaq; } set { if (value == _currentFaq) return; _currentFaq = value; RaisePropertyChanged("CurrentFaq"); } } public void GetFaqsAsync() { _model.GetItemsAsync(); } void Model_GetFaqsComplete(object sender, EntityResultsArgs<faq> e) { if (e.Error != null) { ErrorMessage = e.Error.Message; } else { Faqs = e.Results; } } } And then finally the Silverlight view itself public partial class FrequentlyAskedQuestions { public FrequentlyAskedQuestions() { InitializeComponent(); if (!ViewModelBase.IsInDesignModeStatic) { // Use MEF To load the View Model CompositionInitializer.SatisfyImports(this); } } [Import(ViewModelTypes.FaqViewModel)] public object ViewModel { set { DataContext = value; } } }

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• ASMX Web Services with SOAP Extension

  - by digitall

  I am in the process of setting up a web service for an external client to connect to my client's application and update some information. I went the ASMX route (the rest of the application runs on WCF) because I knew the external client could be very difficult to deal with and I was trying to keep everything as simple as possible. They also aren't a .Net shop which makes things worse. After getting the service setup for them I provided the ASMX URL for them to see how to format the SOAP headers/message content. They have since come back and told me their tool is unable to send them in the format required by .Net and I can either come up with a different way to accept messages or we have to go with FTP. Based on this I have been researching how to intercept their message, reformat it the way my service requires it (which means adding two lines), and then let it process. This path led me to SOAP Extensions which I have been trying to work with but can't seem to figure out. When I have my sample application call the web service from the generated code Add Web Reference provides everything works great until I add in my extension. All it currently does is override ChainStream setting an internal stream equal to the one being passed in and returning a new stream, like this: private Stream newStream = null; private Stream oldStream = null; public override Stream ChainStream(Stream stream) { this.oldStream = stream; this.newStream = new MemoryStream(); return newStream; } I also override ProcessMessage and in it take the contents of oldStream and set newStream equal to that and then write to a different stream with an XmlWriter. I take that new stream and using a StreamReader read it into a string, with the end goal being manipulating it here and setting newStream (which is being used by ChainStream) equal to the contents of this. Here is that piece: public override void ProcessMessage(SoapMessage message) { switch (message.Stage) { case SoapMessageStage.BeforeDeserialize: this.Process(); break; default: break; } } private void Process() { this.newStream.Position = 0L; XmlTextReader reader = new XmlTextReader(this.oldStream); MemoryStream outStream = new MemoryStream(); using (XmlWriter writer = XmlWriter.Create(outStream)) { do { writer.WriteNode(reader, true); } while (reader.Read()); writer.Flush(); } outStream.Seek(0, SeekOrigin.Begin); StreamReader streamReader = new StreamReader(outStream); string message = streamReader.ReadToEnd(); newStream = outStream; newStream.Seek(0, SeekOrigin.Begin); streamReader.Close(); } By running this, which seems to me like it would be fine, my test application gets a 400 Bad Request back from the service. If I either don't use the extension or I don't do anything in ProcessMessage everything seems fine. Any suggestions to this? As a side note, once I get this working with the generated code from the WSDL I will be moving to a WebRequest to try sending the message to the service. Currently that bombs out with a 415 Unsupported Media Type response. I'm trying to keep this post to one question but if anyone has any tips with using a WebRequest to connect to an ASMX service it would be much appreciated!

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