Re: tracking commit timestamps

On 05/01/15 17:50, Petr Jelinek wrote:
> On 05/01/15 16:17, Petr Jelinek wrote:
>> On 05/01/15 07:28, Fujii Masao wrote:
>>> On Thu, Dec 4, 2014 at 12:08 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
>>> wrote:
>>>> On Wed, Dec 3, 2014 at 11:54 PM, Alvaro Herrera
>>>> <alvherre(at)2ndquadrant(dot)com> wrote:
>>>>> Pushed with some extra cosmetic tweaks.
>>>>
>>>> I got the following assertion failure when I executed
>>>> pg_xact_commit_timestamp()
>>>> in the standby server.
>>>>
>>>> =# select pg_xact_commit_timestamp('1000'::xid);
>>>> TRAP: FailedAssertion("!(((oldestCommitTs) != ((TransactionId) 0)) ==
>>>> ((newestCommitTs) != ((TransactionId) 0)))", File: "commit_ts.c",
>>>> Line: 315)
>>>> server closed the connection unexpectedly
>>>> This probably means the server terminated abnormally
>>>> before or while processing the request.
>>>> The connection to the server was lost. Attempting reset: 2014-12-04
>>>> 12:01:08 JST sby1 LOG: server process (PID 15545) was terminated by
>>>> signal 6: Aborted
>>>> 2014-12-04 12:01:08 JST sby1 DETAIL: Failed process was running:
>>>> select pg_xact_commit_timestamp('1000'::xid);
>>>>
>>>> The way to reproduce this problem is
>>>>
>>>> #1. set up and start the master and standby servers with
>>>> track_commit_timestamp disabled
>>>> #2. enable track_commit_timestamp in the master and restart the master
>>>> #3. run some write transactions
>>>> #4. enable track_commit_timestamp in the standby and restart the
>>>> standby
>>>> #5. execute "select pg_xact_commit_timestamp('1000'::xid)" in the
>>>> standby
>>>>
>>>> BTW, at the step #4, I got the following log messages. This might be
>>>> a hint for
>>>> this problem.
>>>>
>>>> LOG: file "pg_commit_ts/0000" doesn't exist, reading as zeroes
>>>> CONTEXT: xlog redo Transaction/COMMIT: 2014-12-04 12:00:16.428702+09;
>>>> inval msgs: catcache 59 catcache 58 catcache 59 catcache 58 catcache
>>>> 45 catcache 44 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7
>>>> catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7
>>>> catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 snapshot 2608
>>>> relcache 16384
>>>
>>> This problem still happens in the master.
>>>
>>> Regards,
>>>
>>
>> Attached patch fixes it, I am not sure how happy I am with the way I did
>> it though.
>>
>
> Added more comments and made the error message bit clearer.
>

Fujii, Alvaro, did one of you had chance to look at this fix?

--
Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services