Nobody else is doing anything with Apache but still I see the same errors. Today I'll try to setup nginx to see if it will help.
Best regards, Kirill Zaborsky On Jan 12, 1:39 am, Graham Dumpleton <[email protected]> wrote: > 2010/1/11 qrilka <[email protected]>: > > > Thanks for your reply, Graham. > > It was quite clear before that I need to spend more time on proper > > server configuration (e.g. Apache now isn't quite tuned at least I > > need to separate python from PHP). I will look into you proposal on > > using nginx for proxying long-running requests. > > BTW I removed maximum-requests but still see 'Premature end of script > > headers' messages in error log. > > What could be a reason for that? > > Are there any other restarts for mod_wsgi except changed wsgi file and > > maximum-requests option? > > Could also occur if someone is doing an: > > apachectl graceful > > Ie., Apache graceful restart. > > Can occur here because Apache will allow its own server child process > to keep running until active requests complete, but due to way APR > library handles the other processes such as mod_wsgi daemon processes, > it will kill them off regardless after 3 seconds. Thus, mod_wsgi > daemon process goes away and the Apache server child process proxying > request to the daemon process will then see connection close and get > that error message. > > Presumably an Apache graceful shutdown could cause something similar. > > The question is therefore if anyone is doing graceful restarts on > Apache at same time as you still see the message. > > The only other times that error message could arise is if the mod_wsgi > daemon process crashed, or if someone has sent an explicit signal to > the mod_wsgi daemon process to make it shutdown. > > Graham > > > Many thanks for you help. > > > Best regards, > > Kirill Zaborsky > > > On Jan 11, 3:23 am, Graham Dumpleton <[email protected]> > > wrote: > >> 2010/1/8 qrilka <[email protected]>: > > >> > OK, I'll investigate how that could be solved. > >> > Actually application is very simple and the only problem could be with > >> > some operations on large images. > >> > But I do not see how that could lead to some operations taking more > >> > than 1 second. > > >> That time of 5 seconds isn't just for processing of the image but also > >> inclusive of the time it takes to upload the image to the application > >> if what you are doing first involves an upload. > > >> Thus, if dealing with large images or slow HTTP clients and clients > >> are talking direct to Apache, then you may well exceed that time. > > >> What you can do to partly isolate yourself from problem of slow HTTP > >> clients is to put nginx proxy in front of Apache. At least for files > >> up to some default, nginx will buffer the upload before actually > >> triggering the proxy to the Apache back end. This means that request > >> only passed onto Apache when data is available and so Apache can do > >> its job quickly and not be tied up with dealing with slow HTTP > >> request. Thus less risk of request being interrupted if process does > >> indeed fall within that 5 seconds. Only passing on request when > >> request data available, also means you will get better utilisation > >> from Apache processes/threads and can configure it for less, thus > >> reducing its memory overhead. > > >> Right now I can't find the part of the nginx documentation that talks > >> about request buffering. The proxy documentation tends only to talk > >> about response buffering as far as configuration parameters. > > >> > I though that using maximum-requests could prevent possible memory > >> > leaks and exessive memory consumption. > >> > Isn't it a right supposition? > > >> It can, but as described can cause conflict with long running > >> uploads/requests if they are greater than default shutdown timeout of > >> 5 seconds. You can adjust the shutdown timeout using shutdown-timeout > >> option to WSGIDaemonProcess, but make it too long and you risk > >> perceived delays by user if all daemon mode processes in group restart > >> about the same time. > > >> > And also if I understand it right I will get the same errors on > >> > application update when my WSGI application will be restarted. > > >> Yes, the shutdown timeout comes into play on any self restart of > >> mod_wsgi daemon processes. > > >> The only time that shutdown timeout doesn't apply is when you do a > >> full Apache 'restart' or 'graceful'. In that case Apache itself > >> applies a 3 second timeout and will forcibly kill the mod_wsgi daemon > >> mode processes after that. Can't override that specific Apache > >> timeout. > > >> > Do you have any thoughts how could I find any misbehaving long-running > >> > process with a stacktrace? > > >> One could use WSGI wrappers around your application object to add a > >> request timer, but would first contemplate on whether it is the upload > >> time for file rather than processing time. > > >> Graham > > >> > Best regards, > >> > Kirill Zaborsky > > >> > On Jan 8, 1:06 am, Graham Dumpleton <[email protected]> > >> > wrote: > >> >> 2010/1/8 qrilka <[email protected]>: > > >> >> > From VirtualHost specific log: > >> >> > ------------------------ > >> >> > [Thu Jan 07 21:09:49 2010] [info] mod_wsgi (pid=12366): Maximum > >> >> > requests reached 'av_factory'. > >> >> > [Thu Jan 07 21:09:49 2010] [info] mod_wsgi (pid=12366): Shutdown > >> >> > requested 'av_factory'. > >> >> > [Thu Jan 07 21:09:54 2010] [info] mod_wsgi (pid=12366): Aborting > >> >> > process 'av_factory'. > > >> >> This line indicates that what I described previously is occurring and > >> >> is likely the cause. > > >> >> That is, when reaching maximum-requests, there are long running > >> >> requests or stuck requests that don't complete within the default 5 > >> >> second window for shutting down a daemon process. > > >> >> When that occurs, even though still running the process is forcibly > >> >> exited, even without shutting down Python interpreter properly. As a > >> >> result, the Apache server child process which is proxying that > >> >> specific request to the mod_wsgi daemon mode process sees the > >> >> connection to daemon process abruptly cut off and as such you may see > >> >> errors about premature end of script headers or the various filter > >> >> errors or broken pipe messages depending on where a request was up to. > > >> >> Do you have any idea about whether you legitimately have requests that > >> >> take longer than 5 seconds to process? > > >> >> For what reason are you using maximum-requests in the first place? If > >> >> you don't have to use that option for some reason, the issue should be > >> >> avoided. > > >> >> Graham> [Thu Jan 07 21:09:54 2010] [info] mod_wsgi (pid=28423): Attach > >> >> > interpreter ''. > >> >> > [Thu Jan 07 21:09:54 2010] [info] mod_wsgi (pid=28423): Enable monitor > >> >> > thread in process 'av_factory'. > >> >> > [Thu Jan 07 21:09:54 2010] [info] mod_wsgi (pid=28423): Enable > >> >> > deadlock thread in process 'av_factory'. > >> >> > [Thu Jan 07 21:09:54 2010] [info] [client 188.113.58.162] mod_wsgi > > >> > -- > >> > You received this message because you are subscribed to the Google > >> > Groups "modwsgi" group. > >> > To post to this group, send email to [email protected]. > >> > To unsubscribe from this group, send email to > >> > [email protected]. > >> > For more options, visit this group > >> > athttp://groups.google.com/group/modwsgi?hl=en. > > > -- > > You received this message because you are subscribed to the Google Groups > > "modwsgi" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group > > athttp://groups.google.com/group/modwsgi?hl=en. > >
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