On Wed, Mar 30, 2016 at 11:43 PM, Masahiko Sawada <sawada.m...@gmail.com> wrote:
> On Tue, Mar 29, 2016 at 5:36 PM, Kyotaro HORIGUCHI
> <horiguchi.kyot...@lab.ntt.co.jp> wrote:
>> I personally don't think it needs such a survive measure. It is
>> very small syntax and the parser reads very short text. If the
>> parser failes in such mode, something more serious should have
>> occurred.
>> At Tue, 29 Mar 2016 16:51:02 +0900, Fujii Masao <masao.fu...@gmail.com> 
>> wrote in <cahgqgwfth8pnyhalbx0nf8o4qmwctdzeocwrqeu7howgdjg...@mail.gmail.com>
>>> On Tue, Mar 29, 2016 at 4:23 PM, Kyotaro HORIGUCHI
>>> <horiguchi.kyot...@lab.ntt.co.jp> wrote:
>>> > Hello,
>>> >
>>> > At Mon, 28 Mar 2016 18:38:22 +0900, Masahiko Sawada 
>>> > <sawada.m...@gmail.com> wrote in 
>>> > <cad21aoajmdv1eukmfeyav24arx4pzujghyby4zxzkpkicuv...@mail.gmail.com>
>>> > sawada.mshk> On Mon, Mar 28, 2016 at 5:50 PM, Kyotaro HORIGUCHI
>>> >> <horiguchi.kyot...@lab.ntt.co.jp> wrote:
>>> > As mentioned in my comment, SQL parser converts yy_fatal_error
>>> > into ereport(ERROR), which can be caught by the upper PG_TRY (by
>>> > #define'ing fprintf). So it is doable if you mind exit().
>>> I'm afraid that your idea doesn't work in postmaster. Because 
>>> ereport(ERROR) is
>>> implicitly promoted to ereport(FATAL) in postmaster. IOW, when an internal
>>> flex fatal error occurs, postmaster just exits instead of jumping out of 
>>> parser.
>> If The ERROR may be LOG or DEBUG2 either, if we think the parser
>> fatal erros are recoverable. guc-file.l is doing so.
>>> ISTM that, when an internal flex fatal error occurs, it's
>>> better to elog(FATAL) and terminate the problematic
>>> process. This might lead to the server crash (e.g., if
>>> postmaster emits a FATAL error, it and its all child processes
>>> will exit soon). But probably we can live with this because the
>>> fatal error basically rarely happens.
>> I agree to this
>>> OTOH, if we make the process keep running even after it gets an internal
>>> fatal error (like Sawada's patch or your idea do), this might cause more
>>> serious problem. Please imagine the case where one walsender gets the fatal
>>> error (e.g., because of OOM), abandon new setting value of
>>> synchronous_standby_names, and keep running with the previous setting value.
>>> OTOH, the other walsender processes successfully parse the setting and
>>> keep running with new setting. In this case, the inconsistency of the 
>>> setting
>>> which each walsender is based on happens. This completely will mess up the
>>> synchronous replication.
>> On the other hand, guc-file.l seems ignoring parser errors under
>> normal operation, even though it may cause similar inconsistency,
>> if any..
>> | LOG:  received SIGHUP, reloading configuration files
>> | LOG:  input in flex scanner failed at file 
>> "/home/horiguti/data/data_work/postgresql.conf" line 1
>> | LOG:  configuration file "/home/horiguti/data/data_work/postgresql.conf" 
>> contains errors; no changes were applied
>>> Therefore, I think that it's better to make the problematic process exit
>>> with FATAL error rather than ignore the error and keep it running.
>> +1. Restarting walsender would be far less harmful than keeping
>> it running in doubtful state.
>> Sould I wait for the next version or have a look on the latest?
> Attached latest patch incorporate some review comments so far, and is
> rebased against current HEAD.

Sorry I attached wrong patch.
Attached patch is correct patch.


Masahiko Sawada

Attachment: multi_sync_replication_v21.patch
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