[Pgpool-general] The Unplugged wire

Wed Mar 3 00:34:04 UTC 2010

Daniel,

I have committed fix into CVS HEAD. Could you try it out?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

> Thanks to you Tatsuo,...
> 
> I am glad  my report helped you! As soon as you tell me it is done I will
> start testing/debugging it again.
> 
> 2010/3/2 Tatsuo Ishii <ishii at sraoss.co.jp>
> 
> > Daniel,
> >
> > Thanks for the report!
> >
> > > I spoke in another message about this problem, yet, I debugged deeper and
> > I
> > > have more specific information, that, maybe, can be usefull.
> > > (The thread I spoke something about was:
> > >
> > http://lists.pgfoundry.org/pipermail/pgpool-general/2010-February/002565.html
> > > )
> > >
> > > I am working with two VB Virtual machines with CentOS 5 (i386). Running
> > > PostgreSQL 8.3.9 and pgpool 2.3.2.1.
> > >
> > > The test was simple. While I was inserting values every second, I
> > unplugged
> > > one of the nodes.
> > > health check is every second and it's timeout is 2 seconds.
> > >
> > > In that moment all inserts stops, and pgpool waits.
> > > The point where it stops is:
> > >
> > > [...]
> > > [pid 29444] 10:47:55.537470 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> > > [pid 29444] 10:47:55.537591 socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 9
> > > [pid 29444] 10:47:55.537726 setsockopt(9, SOL_TCP, TCP_NODELAY, [1], 4) =
> > 0
> > > [pid 29444] 10:47:55.537886 connect(9, {sa_family=AF_INET,
> > > sin_port=htons(5432), sin_addr=inet_addr("192.168.1.10")}, 16) = ?
> > > ERESTARTSYS (To be restarted)
> > > [pid 29444] 10:47:56.529113 --- SIGALRM (Alarm clock) @ 0 (0) ---
> > > [pid 29444] 10:47:56.529235 rt_sigprocmask(SIG_SETMASK, ~[ILL TRAP ABRT
> > BUS
> > > FPE SEGV CONT SYS RTMIN RT_1], NULL, 8) = 0
> > > [pid 29444] 10:47:56.529428 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> > > [pid 29444] 10:47:56.529602 sigreturn() = ? (mask now [])
> > > [pid 29444] 10:47:56.529894 connect(9, {sa_family=AF_INET,
> > > sin_port=htons(5432), sin_addr=inet_addr("192.168.1.10")}, 16 <unfinished
> > > ...>
> > >
> > >
> > > First it does a connect() wich receives de SIGALARM, and continues. But
> > then
> > > it does another connect(), and this time it does not receive any
> > SIGALARM,
> > > so, it waits (I think) till the system closes the connection.
> > >
> > > After waiting (too long) it starts working again (now with the node
> > down):
> > >
> > > [...]
> > > [pid 29445] 10:49:30.273727 <... connect resumed> ) = -1 EHOSTUNREACH (No
> > > route to host)
> > > [pid 29444] 10:49:30.274739 <... connect resumed> ) = -1 EHOSTUNREACH (No
> > > route to host)
> > > [pid 29445] 10:49:30.274809 rt_sigprocmask(SIG_SETMASK, ~[ILL TRAP ABRT
> > BUS
> > > FPE SEGV CONT SYS RTMIN RT_1], [], 8) = 0
> > > [pid 29445] 10:49:30.275057 time(NULL)  = 1267436970
> > > [pid 29445] 10:49:30.275202 stat64("/etc/localtime",
> > {st_mode=S_IFREG|0644,
> > > st_size=2593, ...}) = 0
> > > [pid 29445] 10:49:30.275485 write(2, "2010-03-01 10:49:30 ERROR: pid
> > 2"...,
> > > 1012010-03-01 10:49:30 ERROR: pid 29445: connect_inet_domain_socket:
> > > connect() failed: No route to host
> > > ) = 101
> > > [pid 29445] 10:49:30.275911 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> > > [pid 29445] 10:49:30.276062 close(7)    = 0
> > > [pid 29445] 10:49:30.276221 rt_sigprocmask(SIG_SETMASK, ~[ILL TRAP ABRT
> > BUS
> > > FPE SEGV CONT SYS RTMIN RT_1], [], 8) = 0
> > > [pid 29445] 10:49:30.276389 time(NULL)  = 1267436970
> > > [pid 29445] 10:49:30.276715 stat64("/etc/localtime",
> > {st_mode=S_IFREG|0644,
> > > st_size=2593, ...}) = 0
> > > [pid 29445] 10:49:30.276895 write(2, "2010-03-01 10:49:30 ERROR: pid
> > 2"...,
> > > 782010-03-01 10:49:30 ERROR: pid 29445: connection to 192.168.1.10(5432)
> > > failed
> > > ) = 78
> > > [...]
> > >
> > > As you can see it restarts after 1 min and a half (wich is too much). It
> > is
> > > always the same (without changeing any system values)
> > >
> > > If it is necessary I can show more debug lines.
> > >
> > > Looking trough the source, we think, maybe it could be a problem with the
> > > connection being blocked. Maybe, it would be possible not to block it
> > > (speaking about the socket).
> > > We suppose something is happening in pool_connection_pool.c arround line
> > 473
> > > ("connect_inet_domain_socket_by_port").
> > >
> > > Or maybe I am doing something wrong,... does anybody else tested the
> > > "unpluged wire" ? Is it working?
> >
> > What health_check() does here is:
> >
> > start alarm (done by caller of health_check)
> > connect()
> > write()
> > read()
> > :
> > :
> >
> > If the wire is unplugged, one of system calls will be blocked and
> > eventually alarm interrupt any of connect/write/read and health_check
> > returns with error code. Write() and read() are fine. Problem is,
> > connect is done by connect_inet_domain_socket_by_port, which does
> > retry if connect() is interrupted by a system call.
> >
> > I belive what you saw was that.
> > > First it does a connect() wich receives de SIGALARM, and continues. But
> > then
> > > it does another connect(), and this time it does not receive any
> > SIGALARM,
> > > so, it waits (I think) till the system closes the connection.
> >
> > The retry should be turn off if it's called from health_check(). Will
> > fix.
> >
> > Thanks again for good testing and analysis.
> > --
> > Tatsuo Ishii
> > SRA OSS, Inc. Japan
> > English: http://www.sraoss.co.jp/index_en.php
> > Japanese: http://www.sraoss.co.jp
> >