[Pgpool-general] seemingly hung pgpool process consuming 100% CPU

Lonni J Friedman netllama at gmail.com
Wed Nov 23 14:53:52 UTC 2011 

Not wanting to be impatient, but I'm very concerned about this
problem, since its impossible to predict when it will occur.  Is there
additional information that I can provide to investigate this further?

thanks

On Tue, Nov 22, 2011 at 10:11 AM, Lonni J Friedman <netllama at gmail.com> wrote:
> This hadn't reproduced in a long time, but we ugpraded to pgpool-3.1 a
> week ago, and this morning I found a pgpool process that was consuming
> 100% CPU, and had been running for a week (although wasn't consuming
> 100% CPU the entire time).  Something else weird is that it showed an
> active, idle connection from a client system which had only been up
> for the past 21 hours.  Anyway, here's the backtrace from the process
> (gdb hung at the very bottom):
>
> [root ~]# gdb pgpool 31293
> GNU gdb (GDB) Red Hat Enterprise Linux (7.1-29.el6)
> Copyright (C) 2010 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 /usr/sbin/pgpool...Reading symbols from
> /usr/lib/debug/usr/sbin/pgpool.debug...done.
> done.
> Attaching to program: /usr/sbin/pgpool, process 31293
> Reading symbols from /usr/lib64/libpq.so.5...(no debugging symbols
> found)...done.
> Loaded symbols for /usr/lib64/libpq.so.5
> Reading symbols from /usr/lib64/libpcp.so.0...Reading symbols from
> /usr/lib/debug/usr/lib64/libpcp.so.0.0.0.debug...done.
> done.
> Loaded symbols for /usr/lib64/libpcp.so.0
> Reading symbols from /lib64/libpam.so.0...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libpam.so.0
> Reading symbols from /usr/lib64/libssl.so.10...(no debugging symbols
> found)...done.
> Loaded symbols for /usr/lib64/libssl.so.10
> Reading symbols from /usr/lib64/libcrypto.so.10...(no debugging
> symbols found)...done.
> Loaded symbols for /usr/lib64/libcrypto.so.10
> Reading symbols from /lib64/libcrypt.so.1...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libcrypt.so.1
> Reading symbols from /lib64/libresolv.so.2...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libresolv.so.2
> Reading symbols from /lib64/libnsl.so.1...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libnsl.so.1
> Reading symbols from /lib64/libm.so.6...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libm.so.6
> Reading symbols from /lib64/libc.so.6...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libc.so.6
> Reading symbols from /lib64/libgssapi_krb5.so.2...(no debugging
> symbols found)...done.
> Loaded symbols for /lib64/libgssapi_krb5.so.2
> Reading symbols from /usr/lib64/libldap_r-2.4.so.2...(no debugging
> symbols found)...done.
> Loaded symbols for /usr/lib64/libldap_r-2.4.so.2
> Reading symbols from /lib64/libpthread.so.0...(no debugging symbols
> found)...done.
> [Thread debugging using libthread_db enabled]
> Loaded symbols for /lib64/libpthread.so.0
> Reading symbols from /lib64/libaudit.so.1...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libaudit.so.1
> Reading symbols from /lib64/libdl.so.2...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libdl.so.2
> Reading symbols from /lib64/libkrb5.so.3...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libkrb5.so.3
> Reading symbols from /lib64/libcom_err.so.2...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libcom_err.so.2
> Reading symbols from /lib64/libk5crypto.so.3...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libk5crypto.so.3
> Reading symbols from /lib64/libz.so.1...(no debugging symbols found)...done.
> Loaded symbols for /lib64/libz.so.1
> Reading symbols from /usr/lib64/libfreebl3.so...(no debugging symbols
> found)...done.
> Loaded symbols for /usr/lib64/libfreebl3.so
> Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging
> symbols found)...done.
> Loaded symbols for /lib64/ld-linux-x86-64.so.2
> Reading symbols from /lib64/libkrb5support.so.0...(no debugging
> symbols found)...done.
> Loaded symbols for /lib64/libkrb5support.so.0
> Reading symbols from /lib64/libkeyutils.so.1...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libkeyutils.so.1
> Reading symbols from /usr/lib64/liblber-2.4.so.2...(no debugging
> symbols found)...done.
> Loaded symbols for /usr/lib64/liblber-2.4.so.2
> Reading symbols from /usr/lib64/libsasl2.so.2...(no debugging symbols
> found)...done.
> Loaded symbols for /usr/lib64/libsasl2.so.2
> Reading symbols from /lib64/libselinux.so.1...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libselinux.so.1
> Reading symbols from /lib64/libnss_files.so.2...(no debugging symbols
> found)...done.
> Loaded symbols for /lib64/libnss_files.so.2
> 0x00000000004192c0 in pool_process_query (frontend=0x2dd8fd0,
> backend=0x187d540,
>    reset_request=<value optimized out>) at pool_process_query.c:379
> 379                             if (!pool_read_buffer_is_empty(MASTER(backend)) ||
> pool_is_query_in_progress())
> Missing separate debuginfos, use: debuginfo-install
> audit-libs-2.0.4-1.el6.x86_64 cyrus-sasl-lib-2.1.23-8.el6.x86_64
> glibc-2.12-1.7.el6.x86_64 keyutils-libs-1.4-1.el6.x86_64
> krb5-libs-1.8.2-3.el6.x86_64 libcom_err-1.41.12-3.el6.x86_64
> libselinux-2.0.94-2.el6.x86_64
> nss-softokn-freebl-3.12.7-1.1.el6.x86_64 openldap-2.4.19-15.el6.x86_64
> openssl-1.0.0-4.el6.x86_64 pam-1.1.1-4.el6.x86_64
> postgresql-libs-8.4.4-2.el6.x86_64 zlib-1.2.3-25.el6.x86_64
> (gdb) bt
> #0  0x00000000004192c0 in pool_process_query (frontend=0x2dd8fd0,
> backend=0x187d540,
>    reset_request=<value optimized out>) at pool_process_query.c:379
> #1  0x000000000040ae42 in do_child (unix_fd=3, inet_fd=<value
> optimized out>) at child.c:354
> #2  0x00000000004054c5 in fork_a_child (unix_fd=3, inet_fd=4, id=152)
> at main.c:1072
> #3  0x0000000000407b1c in main (argc=<value optimized out>,
> argv=<value optimized out>)
>    at main.c:549
> (gdb) cont
> Continuing.
>
> On Tue, Sep 20, 2011 at 9:25 AM, Lonni J Friedman <netllama at gmail.com> wrote:
>> Nevermind, I figured out what I was doing wrong.  Now I just need for
>> this to hang again.
>>
>> On Tue, Sep 20, 2011 at 9:08 AM, Lonni J Friedman <netllama at gmail.com> wrote:
>>> I tried to do that, but pgpool refuses to start reporting:
>>> -bash: /usr/lib/debug/usr/sbin/pgpool.debug: bad ELF interpreter: No
>>> such file or directory
>>>
>>> I'm puzzled why it fails, as it was built on the same server where I
>>> built the (working) release build of pgpool.
>>>
>>> $ file /usr/lib/debug/usr/sbin/pgpool.debug
>>> /usr/lib/debug/usr/sbin/pgpool.debug: ELF 64-bit LSB executable,
>>> x86-64, version 1 (GNU/Linux), dynamically linked (uses shared libs),
>>> for GNU/Linux 2.6.18, not stripped
>>> $ file /usr/sbin/pgpool
>>> /usr/sbin/pgpool: ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
>>> dynamically linked (uses shared libs), for GNU/Linux 2.6.18, stripped
>>>
>>>
>>>
>>>
>>> On Mon, Sep 19, 2011 at 7:10 PM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
>>>> It's really hard to find the cause of the problem from a stack trace
>>>> without symbol tables... Is it possible to reinstalll pgpool binary
>>>> with debug symbols?
>>>> --
>>>> Tatsuo Ishii
>>>> SRA OSS, Inc. Japan
>>>> English: http://www.sraoss.co.jp/index_en.php
>>>> Japanese: http://www.sraoss.co.jp
>>>>
>>>>> This happened again.  I ran the gdb command that you requested,
>>>>> however it occurred to me that the output may not be all that useful
>>>>> since I'm not running a debug build of pgpool:
>>>>> ###############
>>>>> # gdb pgpool 2343
>>>>> GNU gdb (GDB) Red Hat Enterprise Linux (7.1-29.el6)
>>>>> Copyright (C) 2010 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 /usr/sbin/pgpool...(no debugging symbols found)...done.
>>>>> Attaching to program: /usr/sbin/pgpool, process 2343
>>>>> Reading symbols from /usr/lib64/libpq.so.5...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /usr/lib64/libpq.so.5
>>>>> Reading symbols from /usr/lib64/libpcp.so.0...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /usr/lib64/libpcp.so.0
>>>>> Reading symbols from /lib64/libpam.so.0...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libpam.so.0
>>>>> Reading symbols from /usr/lib64/libssl.so.10...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /usr/lib64/libssl.so.10
>>>>> Reading symbols from /usr/lib64/libcrypto.so.10...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /usr/lib64/libcrypto.so.10
>>>>> Reading symbols from /lib64/libcrypt.so.1...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libcrypt.so.1
>>>>> Reading symbols from /lib64/libresolv.so.2...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libresolv.so.2
>>>>> Reading symbols from /lib64/libnsl.so.1...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libnsl.so.1
>>>>> Reading symbols from /lib64/libm.so.6...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libm.so.6
>>>>> Reading symbols from /lib64/libc.so.6...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libc.so.6
>>>>> Reading symbols from /lib64/libgssapi_krb5.so.2...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /lib64/libgssapi_krb5.so.2
>>>>> Reading symbols from /usr/lib64/libldap_r-2.4.so.2...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /usr/lib64/libldap_r-2.4.so.2
>>>>> Reading symbols from /lib64/libpthread.so.0...(no debugging symbols
>>>>> found)...done.
>>>>> [Thread debugging using libthread_db enabled]
>>>>> Loaded symbols for /lib64/libpthread.so.0
>>>>> Reading symbols from /lib64/libaudit.so.1...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libaudit.so.1
>>>>> Reading symbols from /lib64/libdl.so.2...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libdl.so.2
>>>>> Reading symbols from /lib64/libkrb5.so.3...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libkrb5.so.3
>>>>> Reading symbols from /lib64/libcom_err.so.2...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libcom_err.so.2
>>>>> Reading symbols from /lib64/libk5crypto.so.3...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libk5crypto.so.3
>>>>> Reading symbols from /lib64/libz.so.1...(no debugging symbols found)...done.
>>>>> Loaded symbols for /lib64/libz.so.1
>>>>> Reading symbols from /usr/lib64/libfreebl3.so...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /usr/lib64/libfreebl3.so
>>>>> Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /lib64/ld-linux-x86-64.so.2
>>>>> Reading symbols from /lib64/libkrb5support.so.0...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /lib64/libkrb5support.so.0
>>>>> Reading symbols from /lib64/libkeyutils.so.1...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libkeyutils.so.1
>>>>> Reading symbols from /usr/lib64/liblber-2.4.so.2...(no debugging
>>>>> symbols found)...done.
>>>>> Loaded symbols for /usr/lib64/liblber-2.4.so.2
>>>>> Reading symbols from /usr/lib64/libsasl2.so.2...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /usr/lib64/libsasl2.so.2
>>>>> Reading symbols from /lib64/libselinux.so.1...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libselinux.so.1
>>>>> Reading symbols from /lib64/libnss_files.so.2...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libnss_files.so.2
>>>>> Reading symbols from /lib64/libnss_dns.so.2...(no debugging symbols
>>>>> found)...done.
>>>>> Loaded symbols for /lib64/libnss_dns.so.2
>>>>> 0x000000000044790a in ?? ()
>>>>> Missing separate debuginfos, use: debuginfo-install pgpool-II-3.0.4-1.el6.x86_64
>>>>> (gdb) bt
>>>>> #0  0x000000000044790a in ?? ()
>>>>> #1  0x0000000000414547 in ?? ()
>>>>> #2  0x000000000041762e in ?? ()
>>>>> #3  0x000000000040a4cd in ?? ()
>>>>> #4  0x0000000000405345 in ?? ()
>>>>> #5  0x00000000004068dc in ?? ()
>>>>> #6  0x00000000004076dc in ?? ()
>>>>> #7  0x00000031ae41ec5d in __libc_start_main () from /lib64/libc.so.6
>>>>> #8  0x0000000000403bf9 in ?? ()
>>>>> #9  0x00007fff0663cfc8 in ?? ()
>>>>> #10 0x000000000000001c in ?? ()
>>>>> #11 0x0000000000000004 in ?? ()
>>>>> #12 0x00007fff0663d90b in ?? ()
>>>>> #13 0x00007fff0663dfe6 in ?? ()
>>>>> #14 0x00007fff0663dfe6 in ?? ()
>>>>> #15 0x00007fff0663dfe6 in ?? ()
>>>>> #16 0x0000000000000000 in ?? ()
>>>>> (gdb) cont
>>>>> Continuing.
>>>>>
>>>>> ###############
>>>>>
>>>>> The entire session completely hung at the end there.
>>>>>
>>>>>
>>>>> On Wed, Sep 14, 2011 at 3:57 PM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
>>>>>> Please use gdb. For example,
>>>>>>
>>>>>> become postgres user (or root user)
>>>>>> gdb pgpool 29191
>>>>>> bt
>>>>>> cont
>>>>>> bt
>>>>>> cont
>>>>>> :
>>>>>> :
>>>>>> :
>>>>>>
>>>>>> This will give us an idea where it's looping.
>>>>>> --
>>>>>> Tatsuo Ishii
>>>>>> SRA OSS, Inc. Japan
>>>>>> English: http://www.sraoss.co.jp/index_en.php
>>>>>> Japanese: http://www.sraoss.co.jp
>>>>>>
>>>>>>> This problem has returned yet again:
>>>>>>>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>>>>>>> 29191 postgres  20   0 80192  14m 1544 R 89.8  0.2  51:15.91 pgpool
>>>>>>>
>>>>>>> postgres 29191  3.4  0.1  80192 14728 ?        R    Sep13  51:40
>>>>>>> pgpool: lfriedman nightly 10.31.96.84(61698) idle
>>>>>>>
>>>>>>>
>>>>>>> I'd really appreciate some input on how to debug this.
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Sep 9, 2011 at 8:11 AM, Lonni J Friedman <netllama at gmail.com> wrote:
>>>>>>>> No one else has experienced this or has suggestions how to debug it?
>>>>>>>>
>>>>>>>> On Wed, Sep 7, 2011 at 12:49 PM, Lonni J Friedman <netllama at gmail.com> wrote:
>>>>>>>>> Greetings,
>>>>>>>>> I'm running pgpool-3.0.4 on a Linux-x86_64 server serving as a load
>>>>>>>>> balancer for a three server postgresql-9.0.4 cluster (1 master, 2
>>>>>>>>> standby).  I'm seeing strange behavior where a single pgpool process
>>>>>>>>> seems to hang after some period of time, and then consume 100% of the
>>>>>>>>> CPU.  I've seen this behavior happen twice since last Friday (when
>>>>>>>>> pgpool was brought online in my production environment).  At the
>>>>>>>>> moment the current hung process looks like this in 'ps auxww' output:
>>>>>>>>>
>>>>>>>>> postgres 19838 98.7  0.0  68856  2904 ?        R    Sep06 1027:36
>>>>>>>>> pgpool: lfriedman nightly 10.31.45.20(58277) idle
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> In top, I see:
>>>>>>>>>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>>>>>>>>> 19838 postgres  20   0 68856 2904 1072 R 100.0  0.0   1027:29 pgpool
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> When to connect to the process with strace, there is no output, so I'm
>>>>>>>>> guessing the process is stuck spinning somewhere:
>>>>>>>>> # strace -p 19838
>>>>>>>>> Process 19838 attached - interrupt to quit
>>>>>>>>> ...
>>>>>>>>> ^CProcess 19838 detached
>>>>>>>>>
>>>>>>>>> One thing that i'm certain of is that the client IP (10.31.45.20)
>>>>>>>>> associated with the hung process has rebooted at least once since that
>>>>>>>>> process was spawned.  So pgpool seems to be in some confused state, as
>>>>>>>>> the client definitely severed the connection already.  I checked the
>>>>>>>>> pgpool log and there are no explicit references to PID 19838.  I'm at
>>>>>>>>> a loss how to debug this further, but clearly something is wrong
>>>>>>>>> somewhere, and this isn't normal/expected behavior.

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