From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Markus Wanner <markus(at)bluegap(dot)ch> |
Cc: | Alexey Klyukin <alexk(at)commandprompt(dot)com>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Postgres-R: internal messaging |
Date: | 2008-07-23 20:51:42 |
Message-ID: | 11514.1216846302@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Markus Wanner <markus(at)bluegap(dot)ch> writes:
> ... crashes are more difficult. IMO the replication
> manager needs to stay alive during this reinitialization, to keep the
> GCS connection. However, it can easily detach from shared memory
> temporarily (the imessages stuff is the only shmem place it touches,
> IIRC). However, a more difficult aspect is: it must be able to tell if a
> backend has applied its transaction *before* it died or not. Thus, after
> all backends have been killed, the postmaster needs to wait with
> reinitializing shared memory, until the replication manager has consumed
> all its messages. (Otherwise we would risk "losing" local transactions,
> probably also remote ones).
I hope you're not expecting the contents of shared memory to still be
trustworthy after a backend crash. If the manager is working strictly
from its own local memory, then it would be reasonable to operate
as above.
regards, tom lane
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