Ok, i found the timeouts problem: /* we now proceed to read from the client until we get EOF, or until * MAX_SECS_TO_LINGER has passed. the reasons for doing this are * documented in a draft: * * http://www.ics.uci.edu/pub/ietf/http/draft-ietf-http-connection-00.txt * * in a nutshell -- if we don't make this effort we risk causing * TCP RST packets to be sent which can tear down a connection before * all the response data has been sent to the client. */ #define SECONDS_TO_LINGER 2
so this is not so easy that i thought ;-/ Can you tell more about "are other ways of avoiding the restarts"? On 13 Sty, 19:41, grassoalvaro <[email protected]> wrote: > > FWIW, there are other ways of avoiding the restarts by preallocating > > daemon process groups in advance and not using VirtualHost but other > > means of virtual hosting. > > Hmm, this is interesting, any example (docs)? > > On 13 Sty, 12:28, Graham Dumpleton <[email protected]> wrote: > > > On 13 January 2011 22:14, grassoalvaro <[email protected]> wrote: > > > > Thanks. I'll try to modify Apache source code to change that timeout > > > and then make some tests. > > > Have fun trying to work out where to change it. It seems to differ > > between MPMs and I never quite got my head around it completely, or at > > least I have forgotten exactly how it works. Overall It is not > > something I would recommend and increasing the timeout will likely > > only cause other problems. That is, rather than have requests be > > killed, you will cause new requests to stall for a lot longer and > > sites will simply appear to not be responding. > > > > Event if mod_wsgi wan't create for shared hosting - many people use it > > > for this. And it works well (except Apache reloading ;-)) Solution to > > > use one Apache for one client is good but takes too many memory. > > > FWIW, there are other ways of avoiding the restarts by preallocating > > daemon process groups in advance and not using VirtualHost but other > > means of virtual hosting. > > > Graham > > > > Anywany, thanks for information. > > > > On 11 Sty, 23:30, Graham Dumpleton <[email protected]> wrote: > > >> On 11 January 2011 23:06, grassoalvaro <[email protected]> wrote: > > > >> > Thanks for your very useful description. > > >> > Do you know Is there any good reason why apache is killing process > > >> > after 3 seconds? Why no 15 for example? > > > >> It is a hard wired timeout period it applies to Apache child processes > > >> when a 'restart' is applied. When it does a graceful restart, it > > >> handles its own child process differently and lets them run to > > >> completion, but in that graceful restart mode it still kills off > > >> processes after fixed 3 seconds if they are what it regards as other > > >> processes, which is what it regards mod_wsgi daemon processes. > > > >> Note that mod_wsgi was originally intended for self hosting of your > > >> own web applications with daemon mode not actually a part of the > > >> original goals as far as features. The model of how it is implemented > > >> isn't necessarily suited to doing shared hosting, especially where > > >> changes are going to be made often to Apache configuration. > > > >> Graham > > > >> > On 11 Sty, 10:17, Graham Dumpleton <[email protected]> wrote: > > >> >> On 11 January 2011 10:27, grassoalvaro <[email protected]> wrote: > > > >> >> > Ok, short description is not enought. > > > >> >> > My app is an ordering app for shared hosting accounts (for Python > > >> >> > mod_wsgi) and it's based on mod_wsgi also. > > >> >> > App is calling some API method (server-app) which is restarting > > >> >> > apache > > >> >> > after httpd modifications. > > >> >> > The problem is that I can of course use sleep && httpd graceful in > > >> >> > background, but this will kill other (customer apps) connections > > >> >> > after > > >> >> > sleep. > > >> >> > So, is there any method do reload config without killing any > > >> >> > mod_wsgi > > >> >> > connections? > > > >> >> Connections are transient and not permanent. For a well written site > > >> >> connections would be maintained for less than a second. > > > >> >> The way the process restart works for daemon processes, regardless of > > >> >> whether you do an Apache restart or graceful restart, is that when > > >> >> daemon process is signalled to restart, it will stop accepting any > > >> >> more connections. If there are no active connections for current > > >> >> requests it will shutdown process immediately and then restart. Any > > >> >> connections that come during that time effectively queue up with > > >> >> Apache child processes and/or within port 80 socket listener queue. > > >> >> When processes restart, the held over requests will be handled. > > > >> >> In the case that the daemon process still had active requests, then > > >> >> rather than daemon process shutting down and restarting immediately it > > >> >> waits, giving the current requests an opportunity to finish first at > > >> >> what point the process is then shutdown and restarted. The way Apache > > >> >> works however, is that it gives a maximum of three seconds grace to > > >> >> the mod_wsgi daemon processes and if they have not shutdown by then, > > >> >> because of the requests not finishing, Apache will forcibly kill them > > >> >> off and they will be restarted. > > > >> >> The problem you saw was because your request handler was likely > > >> >> blocked in some way on waiting for the Apache process to restart and > > >> >> that very act meant the request didn't complete within the three > > >> >> seconds allowing the process to shutdown cleanly. > > > >> >> Now, as I said, for a well written site, requests should be sub > > >> >> second, only long requests like large file uploads might be affected. > > >> >> So, for typical case, the restart wouldn't usually be noticed and > > >> >> wouldn't affect any connections because outstanding requests would > > >> >> finish within the three seconds dictated by Apache. > > > >> >> Of course, if you are constantly restarting Apache because of > > >> >> configuration changes, then you increase the risk that you will hit a > > >> >> requests that doesn't finish within the three seconds and exit in time > > >> >> to allow process to restart cleanly. > > > >> >> Whether you can avoid doing the restarts I cannot comment because have > > >> >> no idea what changes you are enacting to the Apache configuration > > >> >> which triggers you wanting to restart it. If the changes relate to > > >> >> mod_wsgi daemon process provisioning then for some cases you may be > > >> >> able to avoid it, but it means setting up things in a particular way. > > >> >> Overall, you are often better off having a nginx front end and simply > > >> >> giving each customer their own Apache instance behind that. That way > > >> >> only customer to whom the changes apply are affected and no one else. > > >> >> This is how WebFaction and some other quality Python hosting companies > > >> >> work. > > > >> >> > Regards. > > > >> >> > On 11 Sty, 00:15, Graham Dumpleton <[email protected]> > > >> >> > wrote: > > >> >> >> On 11 January 2011 07:53, grassoalvaro <[email protected]> > > >> >> >> wrote: > > > >> >> >> > Hi. > > > >> >> >> > I have application deployed on apache + mod_wsgi which is > > >> >> >> > changing > > >> >> >> > httpd.conf and then reloading apache (httpd graceful). > > >> >> >> > And here is the problem: application is making request changing > > >> >> >> > httpd > > >> >> >> > config and reloading him and while request is in progress the > > >> >> >> > process > > >> >> >> > is killing: > > > >> >> >> > Premature end of script headers: start.wsgi > > >> >> >> > (2)No such file or directory: mod_wsgi (pid=31624): Unable to > > >> >> >> > connect > > >> >> >> > to WSGI daemon process 'pylons_app' on > > >> >> >> > '/var/logs/wsgi.31409.0.1.sock' > > >> >> >> > after multiple attempts., > > > >> >> >> > So it is possible to reload _only_ apache config without > > >> >> >> > reloading > > >> >> >> > whole mod_wsgi? > > > >> >> >> The short answer is no. > > > >> >> >> > Or any other idea how to deal with this problem? > > > >> >> >> How are you triggering the Apache restart? The daemon processes > > >> >> >> themselves will not have sufficient privileges to do it itself, so > > >> >> >> you > > >> >> >> must be using a separate suid script or invoking a remote API for > > >> >> >> some > > >> >> >> service that does it on your behalf. > > > >> >> >> If it is a command line script, then invoke it as a background > > >> >> >> command > > >> >> >> with a time delay before it. Ie. > > > >> >> >> os.system('(sleep 1; /some/path/restart-apache)&') > > > >> >> >> If it is via a remote API using XML-RPC or something, instead of > > >> >> >> doing > > >> >> >> it from web application, make it a script executed as above. > > > >> >> >> A further way is to create a background thread which calls the API. > > > >> >> >> In all ways, you are attempting to avoid the problem of the request > > >> >> >> handler blocking on waiting for the restart command to complete. > > > >> >> >> Anyway, will help if you explain how you are triggering the Apache > > >> >> >> restart. > > > >> >> >> Graham > > > >> >> > -- > > >> >> > 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 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 at http://groups.google.com/group/modwsgi?hl=en.
