Re: Postgres-R: internal messaging - Mailing list pgsql-hackers

From Markus Wanner
Subject Re: Postgres-R: internal messaging
Date
Msg-id 488832C4.1010003@bluegap.ch
Whole thread Raw
In response to Re: Postgres-R: internal messaging  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Postgres-R: internal messaging  (Markus Wanner <markus@bluegap.ch>)
List pgsql-hackers
Hi,

Tom Lane wrote:
> I hope you're not expecting the contents of shared memory to still be
> trustworthy after a backend crash.

Hm.. that's a good point.

So I either need to bullet-proof the imessages with checksums or some 
such. I'm not sure that's doable reliably. Not to speak about performance.

Thus it might be better to just restart the replication manager as well. 
Note that this means leaving the replication group temporarily and going 
through node recovery to apply remote transactions it has missed in 
between. This sounds expensive, but it's certainly the safer way to do 
it. And as such backend crashes are Expected Not To Happen(tm) on 
production systems, that's probably good enough.

> If the manager is working strictly
> from its own local memory, then it would be reasonable to operate
> as above.

That's not the case... :-(

Thanks for your excellent guidance.

Regards

Markus



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