Re: Support for N synchronous standby servers - take 2

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Support for N synchronous standby servers - take 2
Date: 2016-04-11 11:47:30
Message-ID: CAHGQGwHEAbDfYjyM5jSSJVs-LYsm25n1-5HMUprYS9PCg5Xczg@mail.gmail.com
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On Mon, Apr 11, 2016 at 5:52 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Mon, Apr 11, 2016 at 1:31 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>> On Mon, Apr 11, 2016 at 10:58 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>> On Sat, Apr 9, 2016 at 12:32 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>>> Jeff Janes <jeff(dot)janes(at)gmail(dot)com> writes:
>>>>> When I compile now without cassert, I get the compiler warning:
>>>>
>>>>> syncrep.c: In function 'SyncRepUpdateConfig':
>>>>> syncrep.c:878:6: warning: variable 'parse_rc' set but not used
>>>>> [-Wunused-but-set-variable]
>>>>
>>>> If there's a good reason for that to be an Assert, I don't see it.
>>>> There are no callers of SyncRepUpdateConfig that look like they
>>>> need to, or should expect not to have to, tolerate errors.
>>>> I think the way to fix this is to turn the Assert into a plain
>>>> old test-and-ereport-ERROR.
>>>>
>>>
>>> I've changed the draft patch Amit implemented so that it doesn't parse
>>> twice(check_hook and assign_hook).
>>> So assertion that was in assign_hook is no longer necessary.
>>>
>>> Please find attached.
>>
>> Thanks for the patch!
>>
>> When I emptied s_s_names, reloaded the configration file, set it to 'standby1'
>> and reloaded the configuration file again, the master crashed with
>> the following error.
>>
>> *** glibc detected *** postgres: wal sender process postgres [local]
>> streaming 0/3015F18: munmap_chunk(): invalid pointer:
>> 0x00000000024d9a40 ***
>> ======= Backtrace: =========
>> *** glibc detected *** postgres: wal sender process postgres [local]
>> streaming 0/3015F18: munmap_chunk(): invalid pointer:
>> 0x00000000024d9a40 ***
>> /lib64/libc.so.6[0x3be8e75f4e]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x97dae2]
>> ======= Backtrace: =========
>> /lib64/libc.so.6[0x3be8e75f4e]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(set_config_option+0x12cb)[0x982242]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(SetConfigOption+0x4b)[0x9827ff]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x97dae2]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x988b4e]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(set_config_option+0x12cb)[0x982242]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x98af40]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(SetConfigOption+0x4b)[0x9827ff]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(ProcessConfigFile+0x9f)[0x98a98b]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x988b4e]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x98af40]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7b50fd]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(ProcessConfigFile+0x9f)[0x98a98b]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7b359c]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7b50fd]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(exec_replication_command+0x1a7)[0x7b47b6]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7b359c]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(PostgresMain+0x772)[0x8141b6]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(exec_replication_command+0x1a7)[0x7b47b6]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7896f7]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(PostgresMain+0x772)[0x8141b6]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x788e62]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x7896f7]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x785544]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x788e62]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(PostmasterMain+0x1134)[0x784c08]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x785544]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x6ce12e]
>> /lib64/libc.so.6(__libc_start_main+0xfd)[0x3be8e1ed5d]
>> postgres: wal sender process postgres [local] streaming
>> 0/3015F18(PostmasterMain+0x1134)[0x784c08]
>> postgres: wal sender process postgres [local] streaming 0/3015F18[0x467e99]
>>
>
> Thank you for reviewing.
>
> SyncRepUpdateConfig() seems to be no longer necessary.

Really? I was thinking that something like that function needs to
be called at the beginning of a backend and walsender in
EXEC_BACKEND case. No?

Regards,

--
Fujii Masao

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