[pgpool-hackers: 2315] Re: Segmentation fault in Pgpool child process

[Muhammad Usama]

On Thu, May 4, 2017 at 1:12 PM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> Usama,
>
> Thank you for letting me know it.  The problem only happens when node
> 0 is stopped.  The segfault happens while initializing pgpool child
> process starting up. The bug was introduced in commit
> 18f95017586aacb7254bbccda18ba67c01468483 by me, sigh. Also 3.5 stable
> tree has the same problem. I have pushed fix to 3.6 and 3.5
> stable. More invasive fix was pushed to master branch.
>

Thanks for fixing the issue.

>
> Because the bug is significant, probably we need to release new minor
> versions for 3.5 and 3.6.
>

Yes that is correct, Since there is no way around for the issue and after
the failover of first backend node the Pgpool-II service can effectively
become unavailable because of this issue so we may need to expedite the
next minor release.



Thanks
Best Regards.
Muhammad Usama


> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
> > Hi Ishii-San
> >
> > I am getting the segmentation fault in Pgpool-II child process on master
> > and 3_6 stable branches.
> >
> > Steps to reproduce.
> >
> > 1-) Start the pgpool-II with two backend nodes (both PG up and running).
> > 2-) Stop one backend node (bin/pg_ctl -D data_5432/ stop)
> > 3-) pgpool-II will perform failover.
> > 4-) Connect to Pgpool-II using PSQL after failover is done.
> >
> > Step 4 is producing the segmentation fault
> >
> > The configuration file I was using for testing is attached and see below
> > the stack trace.
> >
> > --stack trace--
> >
> > [usama at localhost pgpool]$ gdb --core /tmp/core_pgpool.97854 bin/pgpool
> > GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-94.el7
> > Copyright (C) 2013 Free Software Foundation, Inc.
> > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.
> html
> >>
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.  Type "show
> copying"
> > and "show warranty" for details.
> > This GDB was configured as "x86_64-redhat-linux-gnu".
> > For bug reporting instructions, please see:
> > <http://www.gnu.org/software/gdb/bugs/>...
> > Reading symbols from
> > /home/usama/work/community/installed/pgpool/bin/pgpool...done.
> > [New LWP 97854]
> > [Thread debugging using libthread_db enabled]
> > Using host libthread_db library "/lib64/libthread_db.so.1".
> > Core was generated by `pgpool: usama postgres  idle
> >                          '.
> > Program terminated with signal 11, Segmentation fault.
> > #0  0x0000000000422f21 in select_load_balancing_node () at
> > protocol/child.c:1669
> > 1669 char *database = MASTER_CONNECTION(ses->backend)->sp->database;
> > Missing separate debuginfos, use: debuginfo-install
> > audit-libs-2.6.5-3.el7.x86_64 cyrus-sasl-lib-2.1.26-20.el7_2.x86_64
> > glibc-2.17-157.el7.x86_64 keyutils-libs-1.5.8-3.el7.x86_64
> > krb5-libs-1.14.1-27.el7_3.x86_64 libcap-ng-0.7.5-4.el7.x86_64
> > libcom_err-1.42.9-9.el7.x86_64 libgcc-4.8.5-11.el7.x86_64
> > libmemcached-1.0.16-5.el7.x86_64 libselinux-2.5-6.el7.x86_64
> > libstdc++-4.8.5-11.el7.x86_64 nspr-4.13.1-1.0.el7_3.x86_64
> > nss-3.28.2-1.6.el7_3.x86_64 nss-softokn-freebl-3.16.2.3-14.4.el7.x86_64
> > nss-util-3.28.2-1.1.el7_3.x86_64 openldap-2.4.40-13.el7.x86_64
> > openssl-libs-1.0.1e-60.el7_3.1.x86_64 pam-1.1.8-18.el7.x86_64
> > pcre-8.32-15.el7_2.1.x86_64 zlib-1.2.7-17.el7.x86_64
> > (gdb) bt
> > #0  0x0000000000422f21 in select_load_balancing_node () at
> > protocol/child.c:1669
> > #1  0x000000000043d935 in pool_init_session_context (frontend=<optimized
> > out>, backend=<optimized out>) at context/pool_session_context.c:97
> > #2  0x0000000000423dee in do_child (fds=fds at entry=0xf41600) at
> > protocol/child.c:350
> > #3  0x00000000004087e5 in fork_a_child (fds=0xf41600, id=3) at
> > main/pgpool_main.c:586
> > #4  0x000000000040bf6e in failover () at main/pgpool_main.c:1952
> > #5  0x000000000040ccce in sigusr1_interupt_processor () at
> > main/pgpool_main.c:1427
> > #6  0x000000000040df9a in PgpoolMain (discard_status=discard_
> status at entry=1
> > '\001', clear_memcache_oidmaps=clear_memcache_oidmaps at entry=0 '\000') at
> > main/pgpool_main.c:436
> > #7  0x0000000000406dbe in main (argc=<optimized out>, argv=<optimized
> out>)
> > at main/main.c:300
> > (gdb)
> >
> >
> > Thanks
> > Best Regards
> > Muhammad Usama
>
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