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. Regards, -- Masahiko Sawada
multi_sync_replication_v21.patch
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