No, I don't see anything like that (at least at the time of the latest 'Premature end' message). Nginx upload module [1] requires some extra work and testing so it is not on the production server yet. I will let know if there will be any new details on this issue. BTW it seems to be quite unlikely that I have some 'special' web application which requires something like a voodoo magic and I don't find any reports about such problems in the internet. It appears to me to be some kind of server misconfiguration but I don't see any new places where that misconfiguration could be.
[1] http://www.grid.net.ru/nginx/upload.en.html Thanks once again. Best regards, Kirill Zaborsky On Jan 13, 2:49 am, Graham Dumpleton <[email protected]> wrote: > 2010/1/13 qrilka <[email protected]>: > > > There is no CGI scripts on that server. > > Just some PHP sites and Django. > > And the message appears in Django virtual host log. > > Be aware that if this is being caused by a process crash, then the > Segmentation Fault message will appear in the main Apache error log > and not in the virtual host specific error log as is Apache parent > monitoring process which is monitoring the fact the process died and > it isn't linked to a specific virtual host. > > So, ensure you are paying attention to any error messages in the main > Apache error log at the same time, including those which aren't > specifically tagged as coming from mod_wsgi. If you find anything of > relevance, then let me know. > > Graham > > > Best regards, > > Kirill Zaborsky > > > On Jan 13, 1:33 am, Graham Dumpleton <[email protected]> > > wrote: > >> 2010/1/13 qrilka <[email protected]>: > > >> > 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. > > >> The message 'Premature end of script headers' also gets generated by > >> broken CGI scripts. So, you need to look quite closely at error logs > >> and ensure that they are in fact linked to a WSGI request. > > >> Graham > > >> > 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. > > >> > -- > >> > 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 > > ... > > read more »
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