Re: Connections to backend not closing
In message <4b71f7a0.2050...@digithi.de>, "Thimo E." writes: >Dear all, > >first of all, varnish is a really nice software! But... :) >...At the moment I have some problems with varnish and its backend >connection(s). > >[..] > >Some time later (at least 5 minutes !) the last entry "CLOSE_WAIT" >disappears but the "FIN_WAIT2" persists, so the webserver still has a >semi-open socket: This is actually per design, varnish keeps backend connections around if they look like they can be reused, and only revisits them when it tries to reuse them, so they may linger for quite a while before varnish discovers they have been closed by the backend. Apart from the socket hanging around, it is harmless. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
Re: Connections to backend not closing
Hello Poul-Henning, thanks for your quick response. I am not sure that this behavour is really harmless, at least its not for me :) After 1 day running varnish I have 140 sockets of the backend webserver in FIN_WAIT2 state, this is quite a lot. (btw; I don't know why FIN_WAIT2 sockets stay for such a long time in that state and don't time out...) With a litte bit more semi-open connections I can get my backend to a state where stops responsing because of "Too many open connections" (I think 256 connections is the limit at the moment). As you can imagine that is quote annoying :) Is there any possibility to say varnish to close "CLOSE_WAIT" connections immediately ? Or do you have other ideas ? Thanks in advance Thimo Am 10.02.2010 11:04, schrieb Poul-Henning Kamp: > In message<4b71f7a0.2050...@digithi.de>, "Thimo E." writes: > >> Dear all, >> >> first of all, varnish is a really nice software! But... :) >> ...At the moment I have some problems with varnish and its backend >> connection(s). >> >> [..] >> >> Some time later (at least 5 minutes !) the last entry "CLOSE_WAIT" >> disappears but the "FIN_WAIT2" persists, so the webserver still has a >> semi-open socket: >> > This is actually per design, varnish keeps backend connections around > if they look like they can be reused, and only revisits them when it > tries to reuse them, so they may linger for quite a while before > varnish discovers they have been closed by the backend. > > Apart from the socket hanging around, it is harmless. > > > ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
Re: Connections to backend not closing
On Wed, Feb 10, 2010 at 4:17 PM, Thimo E. wrote: > After 1 day running varnish I have 140 sockets of the backend webserver > in FIN_WAIT2 state, this is quite a lot. I'm why do you believe this is "a lot"? Do you have evidence that this is causing your server to behave suboptimally? The impact should be no more than a bit of RAM. --Michael ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
Re: Connections to backend not closing
In message , Micha el Fischer writes: >--000e0cd2978a506e4c047f483f78 >> After 1 day running varnish I have 140 sockets of the backend webserver >> in FIN_WAIT2 state, this is quite a lot. Well, yes and no. The normal finwait2 timeout is on the order of most of a day, 60.000 seconds on FreeBSD for instance, so 140 is probably no more than one socket every ten minutes or so. If you look in varnishstat, does the number correlate to the "Backend Conn." activity counters in any way ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
Re: Connections to backend not closing
Hello Poul, hello Michael, >The impact [of sockets in FIN_WAIT2] should be no more than a bit of RAM. I disagree slightly :) The application which is waiting in FIN_WAIT2 has allocated structures, threads which (may or may not) consume CPU time, ... and last but not least the value of max opened sockets will be reduced by those dead sockets. And..as I wrote already..due to that many opened sockets my backend stops responding because of "Too many open connections". Situation after 2 days running varnish: netstat -p: 520 connections in FIN_WAIT2 state varnishstat: ... 438 0.00 0.01 Backend conn. reuses 547 0.00 0.01 Backend conn. was closed 988 0.00 0.02 Backend conn. recycles ... >If you look in varnishstat, does the number correlate to the >"Backend Conn." activity counters in any way ? Poul, the 547 closed backend connections are quite near to 520 FIN_WAIT2 connections. Any suggestions ? Greets Thimo ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
Re: Connections to backend not closing
On 12 February 2010 00:12, Thimo E. wrote: > Hello Poul, hello Michael, > > >The impact [of sockets in FIN_WAIT2] should be no more than a bit of RAM. > I disagree slightly :) The application which is waiting in FIN_WAIT2 has > allocated structures, threads which (may or may not) consume CPU time, > ... and last but not least the value of max opened sockets will be > reduced by those dead sockets. > And..as I wrote already..due to that many opened sockets my backend > stops responding because of "Too many open connections". > > > Situation after 2 days running varnish: > > netstat -p: > 520 connections in FIN_WAIT2 state > > varnishstat: > ... > 438 0.00 0.01 Backend conn. reuses > 547 0.00 0.01 Backend conn. was closed > 988 0.00 0.02 Backend conn. recycles > ... > >>If you look in varnishstat, does the number correlate to the >>"Backend Conn." activity counters in any way ? > > Poul, the 547 closed backend connections are quite near to 520 FIN_WAIT2 > connections. > > Any suggestions ? You might want to increase the ulimit -n for your backend server process. With nginx set up as a proxy, each open connection consumed 4 file descriptors. (The default is normally 1024). Laurence ___ varnish-misc mailing list varnish-misc@projects.linpro.no http://projects.linpro.no/mailman/listinfo/varnish-misc
