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  • Rails - Always have to check exists, and then value?

    - by Jason B
    I am checking to see if a value in a related table exists quite often in my view, in this case, expenses have approvals. If they have not been submitted, then there is no record of them in the approvals table. I am ending up with some really awkward code <% if !expense_item.expense_approval || expense_item.expense_approval.approval_status == 0 %> Is there a way to do an if statement on a value, without having to check if it exists first? Or some default way to set it nil?

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  • Removing "duplicate objects"

    - by keruilin
    Let's say I have an array of objects from the same class, with two attributes of concern here: name and created_at. How do I find objects with the same name (considered dups) in the array, and then delete the duplicate record in the database. The object with the most-recent created_at date, however, is the one that must be deleted.

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  • mysql_affected_rows() always returns 1 even though no row was updated.

    - by happyhardik
    What I am trying to do is: (programmatically) Update status where id is something, if no rows where updated, give error: we cannot find the record with id something, otherwise give message success. Here I am using mysql_affected_rows() to know if a row was updated or not, but it always return 1, so the user gets a success message, even though there was no row updated. Can anyone tell me what could it be?

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  • How to get VS or Xcode warning with something like "x = x++"?

    - by Jim Buck
    In the spirit of undefined behavior associated with sequence points such as “x = ++x” is it really undefined?, how does one get the compiler to complain about such code? Specifically, I am using Visual Studio 2010 and Xcode 4.3.1, the latter for an OSX app, and neither warned me about this. I even cranked up the warnings on VS2010 to "all", and it happily compiled this. (For the record, VS2010's version added 1 to the variable where Xcode's version kept the variable unchanged.)

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  • Create trigger for auto incerment id and default unix datetime

    - by user1804985
    Any one help me to create a trigger for auto increment fld_id and Unix datetime. My table field is fld_id(int),fld_date(number),fld_value(varchar2). My insert query is insert into table (fld_value)values('xxx'); insert into table (fld_value)values('yyy'); I need the table record like this fld_id fld_date fld_value 1 1354357476 xxx 2 1354357478 yyy Please help me to create this.I can't able to do this..

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  • Check mysql_query results if DELETE query worked?

    - by Camran
    I have a DELETE query which deletes a record from a mysql db. is there any way to make sure if the delete was performed or not? I mean, for a query to FIND stuff you do $res=mysql_query($var); $nr=mysql_num_rows($res); and you get nr of rows returned. Is there any similiar method for deletion of records? Thanks

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  • Download a file+

    - by Martin
    Hi, First PHP project and I'm stuck! I wish to allow users to click a button or a link and download a file. However, my PHP must first perform some tasks, choose the right file, record the download event in a db etc. This I can do, but how do I then send the file as a response to the user's click? Thanks for any help.

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  • How to retrieve from two tables with same foriegn key repeated more than once?

    - by Sarenya
    How to display the datas of tables, that are linked by a primay key and foriegn key, where the foriegn key of the data repeats? For ex. I have two tables, ParentTable and Childtable. The primarykey of the Parent table acts as the foriegn key of the Child table. There are more than one record with same ParentId in Child table. How to retrieve them and display in a single Grid or List or any type of view?

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  • MySQL: averaging with nulls...

    - by Zombies
    Is there a simple way I can exclude nulls from affecting the avg? They appear to count as 0, which is not what I want. I simply don't want to take their average into account, yet here is the catch, I can't drop them from the result set, as that record has data on it that I do need.

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  • How to manage sub-domains on WinHost with IIS7 URL Rewrite 2.0?

    - by jrummell
    I'm trying out WinHost and I'm running into some issues with sub-domains. On WinHost, you can have multiple sub-domains per hosting account, but each sub-domain points to the root website. E.g. you can have www.example.com, sub1.example.com, and sub2.example.com but all of them display the content at http://www.example.com/. Other Hosts allow you to point sub-domains to a sub folder in your website. This would allow you to point sub1.example.com to /sub1, sub2.example.com to /sub2 and www.example.com to /. WinHost recommends using an asp/aspx page to redirect http://sub1.example.com to http://sub1.example.com/sub1, which points to /sub1. While that would work, I'd like to not have the subdomain in the url twice. So I tried using IIS7 URL Rewrite to point http://sub1.example.com to /sub1. Ben Powell describes this in detail on his blog. This is great, except Request.ApplicationPath is now /sub1/path/to/current/page.aspx, which breaks ASP.Net Themes (and probably other stuff too). What can I do to fix the ApplicationPath? Is there a better way to accomplish this?

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  • Connection Reset on MySQL query

    - by sunwukung
    OK, I'm flummoxed.(i've asked this question over on Stack too - but I need to get it fixed so I'm asking here too - any help is GREATLY appreciated) I'm trying to execute a query on a database (locally) and I keep getting a connection reset error. I've been using the method below in a generic DAO class to build a query string and pass to Zend_Db API. public function insert($params) { $loop = false; $keys = $values = ''; foreach($params as $k => $v){ if($loop == true){ $keys .= ','; $values .= ','; } $keys .= $this->db->quoteIdentifier($k); $values .= $this->db->quote($v); $loop = true; } $sql = "INSERT INTO " . $this->table_name . " ($keys) VALUES ($values)"; //formatResult returns an array of info regarding the status and any result sets of the query //I've commented that method call out anyway, so I don't think it's that try { $this->db->query($sql); return $this->formatResult(array( true, 'New record inserted into: '.$this->table_name )); }catch(PDOException $e) { return $this->formatResult($e); } } So far, this has worked fine - the errors have been occurring since we generated new tables to record user input. The insert string looks like this: INSERT INTO tablename(`id`,`title`,`summary`,`description`,`keywords`,`type_id`,`categories`) VALUES ('5539','Sample Title','Sample content',' \'Lorem ipsum dolor sit amet, consectetur adipiscing elit. In et pellentesque mauris. Curabitur hendrerit, leo id ultrices pellentesque, est purus mattis ligula, vitae imperdiet neque ligula bibendum sapien. Curabitur aliquet nisi et odio pharetra tincidunt. Phasellus sed iaculis nisl. Fusce commodo mauris et purus vehicula dictum. Nulla feugiat molestie accumsan. Donec fermentum libero in risus tempus elementum aliquam et magna. Fusce vitae sem metus. Aenean commodo pharetra risus, nec pellentesque augue ullamcorper nec. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Nullam vel elit libero. Vestibulum in turpis nunc.\'','this,is,a,sample,array',1,'category title') Here are the parameters it's getting before assembling the query (var_dump): array 'id' => string '1' (length=4) 'title' => string 'Sample Title' (length=12) 'summary' => string 'Sample content' (length=14) 'description' => string '<p>'Lorem ipsum dolor sit amet, consectetur adipiscing elit. In et pellentesque mauris. Curabitur hendrerit, leo id ultrices pellentesque, est purus mattis ligula, vitae imperdiet neque ligula bibendum sapien. Curabitur aliquet nisi et odio pharetra tincidunt. Phasellus sed iaculis nisl. Fusce commodo mauris et purus vehicula dictum. Nulla feugiat molestie accumsan. Donec fermentum libero in risus tempus elementum aliquam et magna. Fusce vitae sem metus. Aenean commodo pharetra risus, nec pellentesque augue'... (length=677) 'keywords' => string 'this,is,a,sample,array' (length=22) 'type_id' => int 1 'categories' => string 'category title' (length=43) The next port of call was checking the limits on the table, since it seems to insert if the length of "description" is around the 300 mark (it varies between 310 - 330). The field limit is set to VARCHAR(1500) and the validation on this field won't allow anything past bigger than 1200 with HTML, 800 without. The real kicker is that if I take this sql string and execute it via the command line, it works fine - so I can't for the life of me figure out what's wrong. I've tried extending the server parameters i.e. http://stackoverflow.com/questions/1964554/unexpected-connection-reset-a-php-or-an-apache-issue So, in a nutshell, I'm stumped. Any ideas?

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  • Cannot join Win7 workstations to Win2k8 domain

    - by wfaulk
    I am trying to connect a Windows 7 Ultimate machine to a Windows 2k8 domain and it's not working. I get this error: Note: This information is intended for a network administrator. If you are not your network's administrator, notify the administrator that you received this information, which has been recorded in the file C:\Windows\debug\dcdiag.txt. DNS was successfully queried for the service location (SRV) resource record used to locate a domain controller for domain "example.local": The query was for the SRV record for _ldap._tcp.dc._msdcs.example.local The following domain controllers were identified by the query: dc1.example.local dc2.example.local However no domain controllers could be contacted. Common causes of this error include: Host (A) or (AAAA) records that map the names of the domain controllers to their IP addresses are missing or contain incorrect addresses. Domain controllers registered in DNS are not connected to the network or are not running. The client is in an office connected remotely via MPLS to the data center where our domain controllers exist. I don't seem to have anything blocking connectivity to the DCs, but I don't have total control over the MPLS circuit, so it's possible that there's something blocking connectivity. I have tried multiple clients (Win7 Ultimate and WinXP SP3) in the one office and get the same symptoms on all of them. I have no trouble connecting to either of the domain controllers, though I have, admittedly, not tried every possible port. ICMP, LDAP, DNS, and SMB connections all work fine. Client DNS is pointing to the DCs, and "example.local" resolves to the two IP addresses of the DCs. I get this output from the NetLogon Test command line utility: C:\Windows\System32>nltest /dsgetdc:example.local Getting DC name failed: Status = 1355 0x54b ERROR_NO_SUCH_DOMAIN I have also created a separate network to emulate that office's configuration that's connected to the DC network via LAN-to-LAN VPN instead of MPLS. Joining Windows 7 computers from that remote network works fine. The only difference I can find between the two environments is the intermediate connectivity, but I'm out of ideas as to what to test or how to do it. What further steps should I take? (Note that this isn't actually my client workstation and I have no direct access to it; I'm forced to do remote hands access to it, which makes some of the obvious troubleshooting methods, like packet sniffing, more difficult. If I could just set up a system there that I could remote into, I would, but requests to that effect have gone unanswered.) 2011-08-25 update: I had DCDIAG.EXE run on a client attempting to join the domain: C:\Windows\System32>dcdiag /u:example\adminuser /p:********* /s:dc2.example.local Directory Server Diagnosis Performing initial setup: Ldap search capabality attribute search failed on server dc2.example.local, return value = 81 This sounds like it was able to connect via LDAP, but the thing that it was trying to do failed. But I don't quite follow what it was trying to do, much less how to reproduce it or resolve it. 2011-08-26 update: Using LDP.EXE to try and make an LDAP connection directly to the DCs results in these errors: ld = ldap_open("10.0.0.1", 389); Error <0x51: Fail to connect to 10.0.0.1. ld = ldap_open("10.0.0.2", 389); Error <0x51: Fail to connect to 10.0.0.2. ld = ldap_open("10.0.0.1", 3268); Error <0x51: Fail to connect to 10.0.0.1. ld = ldap_open("10.0.0.2", 3268); Error <0x51: Fail to connect to 10.0.0.2. This would seem to point fingers at LDAP connections being blocked somewhere. (And 0x51 == 81, which was the error from DCDIAG.EXE from yesterday's update.) I could swear I tested this using TELNET.EXE weeks ago, but now I'm thinking that I may have assumed that its clearing of the screen was telling me that it was waiting and not that it had connected. I'm tracking down LDAP connectivity problems now. This update may become an answer.

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  • How to prevent delays associated with IPv6 AAAA records?

    - by Nic
    Our Windows servers are registering IPv6 AAAA records with our Windows DNS servers. However, we don't have IPv6 routing enabled on our network, so this frequently causes stall behaviours. Microsoft RDP is the worst offender. When connecting to a server that has a AAAA record in DNS, the remote desktop client will try IPv6 first, and won't fall back to IPv4 until the connection times out. Power users can work around this by connecting to the IP address directly. Resolving the IPv4 address with ping -4 hostname.foo always works instantly. What can I do to avoid this delay? Disable IPv6 on client? Nope, Microsoft says IPv6 is a mandatory part of the Windows operating system. Too many clients to ensure this is set everywhere consistently. Will cause more problems later when we finally implement IPv6. Disable IPv6 on the server? Nope, Microsoft says IPv6 is a mandatory part of the Windows operating system. Requires an inconvenient registry hack to disable the entire IPv6 stack. Ensuring this is correctly set on all servers is inconvenient. Will cause more problems later when we finally implement IPv6. Mask IPv6 records on the user-facnig DNS recursor? Nope, we're using NLNet Unbound and it doesn't support that. Prevent registration of IPv6 AAAA records on the Microsoft DNS server? I don't think that's even possible. At this point, I'm considering writing a script that purges all AAAA records from our DNS zones. Please, help me find a better way. UPDATE: DNS resolution is not the problem. As @joeqwerty points out in his answer, the DNS records are returned instantly. Both A and AAAA records are immediately available. The problem is that some clients (mstsc.exe) will preferentially attempt a connection over IPv6, and take a while to fall back to IPv4. This seems like a routing problem. The ping command produces a "General failure" error message because the destination address is unroutable. C:\Windows\system32>ping myhost.mydomain Pinging myhost.mydomain [2002:1234:1234::1234:1234] with 32 bytes of data: General failure. General failure. General failure. General failure. Ping statistics for 2002:1234:1234::1234:1234: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), I can't get a packet capture of this behaviour. Running this (failing) ping command does not produce any packets in Microsoft Network Monitor. Similarly, attempting a connection with mstsc.exe to a host with an AAAA record produces no traffic until it does a fallback to IPv4. UPDATE: Our hosts are all using publicly-routable IPv4 addresses. I think this problem might come down to a broken 6to4 configuration. 6to4 behaves differently on hosts with public IP addresses vs RFC1918 addresses. UPDATE: There is definitely something fishy with 6to4 on my network. When I disable 6to4 on the Windows client, connections resolve instantly. netsh int ipv6 6to4 set state disabled But as @joeqwerty says, this only masks the problem. I'm still trying to find out why IPv6 communication on our network is completely non-working.

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  • FastCGI and Apache 500 error intermittently

    - by benkorn1
    Hello, I have a FastCGI (mod_fastcgi)problem. It happens every once in a while, and does not casue a complete server meltdown, just 500 errors. Here are a couple things. First I am using APC so PHP is in control of it's own processes, not FastCGI. Also, I have the webroot set as: /var/www/html And the fcgi-bin inside: /var/www/html/fcgi-bin First off here is the apache error_log: [Fri Jan 07 10:22:39 2011] [error] [client 50.16.222.82] (4)Interrupted system call: FastCGI: comm with server "/var/www/html/fcgi-bin/php.fcgi" aborted: select() failed, referer: http://www.domain.com/ I also ran strace on the 'fcgi-pm' process. Here is a snip from the trace around the time it bombs out: 21725 gettimeofday({1294420603, 14360}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6503 38*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 96595}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6154 23*C /var/www/html/fcgi-bin/php.fcgi - - 6483 28*", 16384) = 92 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 270744}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 5741 38*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 311502}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6064 32*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 365598}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6179 33*C /var/www/html/fcgi-bin/php.fcgi - - 5906 59*", 16384) = 92 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 454405}, NULL) = 0 I noticed that the 'select()' seems to stay the same regardless, however the read() changes its return from 46 to some other number while it is bombing out. Has anyone seen anything like this. Could this be some sort of file locking? Thanks, Ben

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  • i7 overclocking problem

    - by benwebdev
    Hi everyone, I've got an overclocked system that seems to be misbehaving. When trying to boot up from cold the system just hangs and nothing is output to the screen. Fans are on as they should but nothing happens to finish the boot. From here I have to switch it off then on again and the boot completes. If I go into the tweak menu in the BIOS I'm informed that a boot has failed I've been in touch with Overclockers UK support a bit and theres not yet been a solution. We've mainly been tweaking the voltage for the CPU. Any suggestions? I'm new to Overclocking which is why I got a bundle with OCUK. With this issue happening on Cold Boot too its tricky to test as I have to make a change then wait till the next day. My system is here: Intel Core i7 930 2.80Ghz overclocked to 4GHz Gigabyte X58A-UD3R (BIOS Version: FC) 6GB RAM Power Supply - CoolerMaster Silent Pro M series 700W One suggestion made by OCUK was that maybe its the power supply but I'm not sure and dont have a spare - it's brand new and a pretty expensive piece of kit. Any thoughts on this? Other recomendations for Power? thanks Ben

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  • Server Admin is not allowing me to configure DNS

    - by Clinton Blackmore
    We have a Mac OS X 10.5.8 Server running DNS (and a few other services). When I connect to it (using Server Admin 10.5.3 [which comes from the Server Admin 10.5.7 tools]), and click to look at the DNS settings, all appears normal -- it shows many reverse entries and two top-level domains. However, when I select one of our domains and open the disclosure triangle, the list is empty! [There should be over a dozen entries, and the reverse entries do show up.] If I then tell it I want to add, say, an A Record to the domain, almost everything disappears -- and I am left with a list showing our two domains, one with a disclosure triangle underneath it showing a single entry, and one reverse entry to correspond to the new A record. named appears to be working fine. DNS names resolve. It appears to simply be that Server Admin is having problems with the data on the computer. No one here would have manually created a DNS entry. Now, while I think I've backed up the DNS (I backed up /var/named/, /etc/named.conf, and /etc/dns/, as mentioned here), I'm really not sure if just replacing the files would restore the DNS settings we have if things go south. I am contemplating going to settings and changing the log level from "Information" to "Debug", but 1) I am just a little concerned that it might write a bad configuration to the disk, and 2) I think it would only affect named and not Server Admin, and, so far as I can tell, named is not having a problem. (Nothing looks strange in /Library/Logs/named.log when I open it via Console/Terminal. Oddly, though, when I click on the 'log' button for DNS in Server Admin, I see no text at all, just a fully white window. When I look at one of our secondary DNS servers, I am able to see the log file through Server Admin.) This entry appears in the system log when I run Server Admin on the server: Jun 17 09:02:08 od1 Server Admin[3892]: Unexpected call to doMarkConfigurationAsDirty by 'DNS' plugin during updateConfigurationViewFromDescription It seems to occur after I've looked at DNS, look at another service, and then click back on DNS. Think that the most likely cause is a corrupt configuration file, I glanced through all the files that I backed up, and none of them is obviously gobbledygook. Here are some oddities I find when running Server Admin from a remote computer to manage the DNS. When I click to see the log file for DNS, the server starts writing messages like these to its system.log: Jun 17 09:59:04 od1 kernel[0]: Limiting open port RST response from 252 to 250 packets per second Jun 17 09:59:06 od1 kernel[0]: Limiting open port RST response from 258 to 250 packets per second This stops when I click on a different service. The inderterminate progress indicator (the spinning wheel that appears beside the "Revert" and "Save" buttons in the bottom-right corner of Server Admin) looks really strange. As far as I can tell, instead of just spinning and waiting, it is being told to start spinning repeatedly, resulting in a jerky animation. Here are some of the messages being logged on the computer running Server Admin: At startup: *** ERROR: -[GRAxes computeLayout]:1124 - plotRect height = 0.000000 <= 0.0 *** *** ERROR: -[GRChartView computeLayout]:1194 - Layout for overlay axes (0x18758f50) failed. *** (These messages don't concern me too much as they go away for a while if you delete ~/Library/Preferences/com.apple.ServerAdmin.plist). At shutdown: 2010-06-17 10:02:17.202 Server Admin[7770:10b] *** -[GroupTextField windowDidResignKey:]: unrecognized selector sent to instance 0x16e12490 More concerning are these messages: 2010-06-17 09:59:47.269 Server Admin[7770:10b] Unexpected call to doMarkConfigurationAsDirty by 'DNS' plugin during updateConfigurationViewFromDescription Server Admin(7770,0xb0453000) malloc: *** error for object 0x1c115390: double free *** set a breakpoint in malloc_error_break to debug 2010-06-17 10:01:00.795 Server Admin[7770:10b] *** -[ServiceEntry sessionHost]: unrecognized selector sent to instance 0x2af500 Any thoughts on: what the problem is how I can troubleshoot it or how to fix it? If I do need to wipe out DNS and restart, is there a good way to do this?

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  • FastCGI and Apache 500 error intermittently

    - by benkorn1
    I have a FastCGI (mod_fastcgi)problem. It happens every once in a while, and does not casue a complete server meltdown, just 500 errors. Here are a couple things. First I am using APC so PHP is in control of it's own processes, not FastCGI. Also, I have the webroot set as: /var/www/html And the fcgi-bin inside: /var/www/html/fcgi-bin First off here is the apache error_log: [Fri Jan 07 10:22:39 2011] [error] [client 50.16.222.82] (4)Interrupted system call: FastCGI: comm with server "/var/www/html/fcgi-bin/php.fcgi" aborted: select() failed, referer: http://www.domain.com/ I also ran strace on the 'fcgi-pm' process. Here is a snip from the trace around the time it bombs out: 21725 gettimeofday({1294420603, 14360}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6503 38*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 96595}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6154 23*C /var/www/html/fcgi-bin/php.fcgi - - 6483 28*", 16384) = 92 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 270744}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 5741 38*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 311502}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6064 32*", 16384) = 46 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 365598}, NULL) = 0 21725 read(14, "C /var/www/html/fcgi-bin/php.fcgi - - 6179 33*C /var/www/html/fcgi-bin/php.fcgi - - 5906 59*", 16384) = 92 21725 alarm(131) = 0 21725 select(15, [14], NULL, NULL, NULL) = 1 (in [14]) 21725 alarm(0) = 131 21725 gettimeofday({1294420603, 454405}, NULL) = 0 I noticed that the 'select()' seems to stay the same regardless, however the read() changes its return from 46 to some other number while it is bombing out. Has anyone seen anything like this. Could this be some sort of file locking? Thanks, Ben

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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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  • LDAP object class violation: attribute ou not allowed in suffix?

    - by Paramaeleon
    I am about to set up a LDAP directory. It is used as a tool to communicate user permissions from a web application to WebDav file system access, e.g. adding a user to the web platform shall allow login to the file system with the same credentials. There are no other usages intended. Following this German tutorial which encourages the use of the attributes c, o, ou etc. over dc, I configured the following suffix and root: suffix "ou=webtool,o=myOrg,c=de" rootdn "cn=ldapadmin,ou=webtool,o=myOrg,c=de" Server starts and I can connect to it by LDAP Admin, which reports “LDAP error: Object lacks”. Well, there aren’t any objects yet. I now want to create the root and admin elements from shell. I created an init.ldif file: dn: ou=webtool,o=myOrg,c=de objectclass: dcObject objectclass: organization dc: webtool o: webtool dn: cn=ldapadmin,ou=webtool,o=myOrg,c=de objectclass: organizationalRole cn: ldapadmin Trying to load the file runs into an error, telling me that ou is not allowed: server:~ # ldapadd -x -D "cn=ldapadmin,ou=webtool,o=myOrg,c=de" -W -f init.ldif Enter LDAP Password: adding new entry "ou=webtool,o=myOrg,c=de" ldap_add: Object class violation (65) additional info: attribute 'ou' not allowed I am not using ou anywhere except in the suffix, so the question: Isn’t it allowed here? What is allowed here? Here is my answer. I am not allowed to post it as answer for 8 hours, so don’t mind that it is part of the question by now. I will move it outside some day, if I don’t forget to do so. There are numberous dependencies for the creation of elements, and error messages are rather confusing if you don’t know of the concept. The objectclass isn’t necessarily dcObject for the databases’ root node, as it is likely to guess when you read several tutoriales. Instead, it must correspond to the object’s type: Here, for a name starting with ou=, it must be organizationalUnit. I found this piece of information in these tables [Link removed due to restriction: Oops! Your edit couldn't be submitted because: We're sorry, but as a spam prevention mechanism, new users can only post a maximum of two hyperlinks. Earn more than 10 reputation to post more hyperlinks. Link is below]. Further on, the object class dictates which properties must and can be added in the record. Here, organizationalUnit must have an ou: entry and must not have neither dc: nor o: entry. The healthy init.ldif file looks like that: dn: ou=webtool,o=myOrg,c=de objectclass: organizationalUnit ou: LDAP server for my webtool dn: cn=ldapadmin,ou=webtool,o=myOrg,c=de objectclass: organizationalRole cn: ldapadmin Note: The page also states: “While many objectClasses show no MUST attributes you must (ouch) follow any hierarchy […] to determine if this is the really case.” I thought that would mean my root record would have to provide the must fields for c= and o= (c: and o:, respectively) but this isn’t the case. Link in answer is (1): http :// www (dot) zytrax (dot) com/books/ldap/ape/ "Appendix E: LDAP - Object Classes and Attributes"

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  • MX records not correctly updated by the Google DNS servers

    - by Mac_Cain13
    We are currently losing some e-mail and we discovered that this is caused by a wrong DNS setting. We used a CNAME for our MX record an thats not allowed. So about 2 weeks ago we changed it to an A-record to fix the problem. It seems all major DNS services (like OpenDNS and ISPs) have synced their records and are returning correct results on our DNS queries. But Googles DNS service (at 8.8.8.8) is still returning the CNAME values and we still some e-mails are not delivered correctly. Query on OpenDNS: ; <<>> DiG 9.7.3-P3 <<>> mx wrep.nl @208.67.222.222 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51231 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;wrep.nl. IN MX ;; ANSWER SECTION: wrep.nl. 3595 IN MX 10 druif.wrep.nl. ;; Query time: 21 msec ;; SERVER: 208.67.222.222#53(208.67.222.222) ;; WHEN: Fri Nov 25 21:36:58 2011 ;; MSG SIZE rcvd: 47 Query on Google DNS: ; <<>> DiG 9.7.3-P3 <<>> mx wrep.nl @8.8.8.8 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12124 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0 ;; QUESTION SECTION: ;wrep.nl. IN MX ;; ANSWER SECTION: wrep.nl. 2372 IN CNAME druif.wrep.nl. ;; AUTHORITY SECTION: wrep.nl. 572 IN SOA ns0.freshdns.nl. hostmaster.twilightinc.nl. 2011112401 14400 3600 604800 3600 ;; Query time: 94 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Fri Nov 25 21:38:10 2011 ;; MSG SIZE rcvd: 117 So is there anyone who can explain why Google is responding with a different (incorrect) result two weeks after the last change? And how can we get Google to update their DNS records correctly? Any help is very appreciated. (Please note that other domains that are managed by the same DNS servers/tools are working fine.)

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  • MSSQL Timing out, a couple of questions...

    - by user29000
    Hi, About once a week, my MSSQL server is timing out, or rather the machine runs out of RAM. This morning it reached 3.9GB of the available 4, with MSSQL taking up 2.5GB. I'm concerned that i've not configured SQL to release memory as it should, so I ran sp_who2 while the timeouts were occuring to see what process were running. If i could post the CSV datafile i would, however, there were 85 processes in total, mostly related to the Full Text service: FT Gatherer - About 35 of these running under the 'sa' account against the master database with status of either sleeping or background, many were dependant on other processes. Is that normal? MySite database - There were only 5 processes for the one active site/database and all were either sleeping or suspended - but their lastBatch dates were set to 1/12/2020. Is that normal? The datbase is only about 20mb in size the traffic levels are very low, so i'm thinking of maybe limiting the amount of RAM SQL has access to (from unlimted to maybe 2GB). Any thoughts / advise would be appreciated. Mny thanks Ben

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  • LogMeIn style remote access to NAS drive

    - by Mere Development
    I've been asked to setup some remote access to a NAS drive. The NAS drive will sit on a VLAN inside a network that uses a Cisco 891 IS router as gateway. The charity have no SSL-VPN licenses for the Cisco. At present there are no open ports or services on the Cisco itself and ideally we would like to keep it that way for a while, hence the request for a LogMeIn style service that's initiated from inside. We need multiple user access, about 10 max. Using LogMeIn on a machine connected to the NAS would only provide screen sharing I believe, and no concurrent connections (could be wrong?) The end users need to be able to read and write files to the NAS from Mac's and PC's around the globe. Read-only access from Mobile devices would be a bonus but not absolutely necessary. This is for a charity, non-commercial, but they are willing to spend if necessary. Cisco config knowledge is at a minimum so if I can avoid upsetting that delicate device I'll be happy :) Anyone have any clever ideas? I can provide more information on request. Thanks, Ben

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