IIS 7 and Above
My IIS7 keeps stopping - help!
Last post Feb 19, 2008 09:15 PM by jjbunn
Feb 05, 2008 05:41 PM|jjbunn|LINK
Since changing to Vista and IIS7 I am finding that the web server is frequently stopped, returning 503 errors, and needs to be restarted. This happens about every day or so.
I looked at mvolo's excellent pages on diagnosing IIS7 errors, but following the advice there couldn't find anything in the Event logs that indicate what the problem is. Looking at the HTTP error logs in windows\system32\logfiles\httperr I see a lot of:
503 1 Timer_ReqQueue DefaultAppPool
errors, for some large animation files the web service is serving. Could this be a clue to the problem? However, I cannot provoke the problem by fetching one of these large files in a browser.
I'd welcome some advice on what I should check next.
Feb 05, 2008 06:47 PM|Luciano.cl|LINK
503 error , (ref. www.w3.org)
The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated
in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.
Note: The existence of the 503 status code does not imply that a
server must use it when becoming overloaded. Some servers may wish
to simply refuse the connection.
Feb 05, 2008 07:35 PM|jjbunn|LINK
Thanks Luciano. Is the problem then simply that my server is now incapable of handling serving these large files? IIS 6 on much less powerful hardware had no such problems.
I'm wondering if I have some configuration parameter set incorrectly, or if the web server is not able to run at sufficient priority.
Feb 05, 2008 08:13 PM|anilr|LINK
IIS7 on vista has a limit on the number of concurrent requests it will execute, from 3 to 10 depending on the sku - any concurrent requests beyond that number will remain queued in http.sys until one of the current requests is done - if the current requests
take a long time to finish the queued request may be timed out by http.sys which is the error you are seeing - really, if you have more than 10 concurrent users using the server, you need to move to server sku and use windows server 2008 - which does not have
any such limit (similar to windows server 2003).
Feb 05, 2008 09:54 PM|jjbunn|LINK
Hi Anil ... very useful info: thanks. How can I check the number of allowed concurrent requests, and perhaps increase it? I suspect you may have put your finger on my problem :-)
Looks like I need to investigate an upgrade to 2008.
Feb 05, 2008 10:05 PM|anilr|LINK
Home basic and home premium have a limit of 3 and ultimate and professional have a limit of 10.
Feb 19, 2008 06:33 PM|jjbunn|LINK
I am running Vista Business: what is the limit for that?
Prior to these problems I was running XP Pro, and never had issues with 503 server unavailable.
Feb 19, 2008 08:56 PM|Enterhost_Nathan|LINK
XP Pro has a 10 concurrent connection limit as well; if you never experienced this issue before when running your website there, then I'd be led to believe that you had never reached the limit until recently.
Feb 19, 2008 09:15 PM|jjbunn|LINK
Thanks Nathan ... although the theory doesn't fit the fact that my logs show access has flattened off in the last year or so, and so I am not getting any more visitors than I used to.
Having said that, how do I look at the number of concurrent accesses on IIS? Is netstat -a the best way? I would like to be sure that I really am hitting that limit of 10, rather than it being some other problem.
Right now, I find my service unavailable 50% of the times I check it, and am having to restart it at least daily.