[pgpool-hackers: 91] Re: "COMMIT" sent to read-only slave in streaming replication

[Tatsuo Ishii]

Thanks for the report. I need more info however. What version is
pgpool-II?

> load balancing with no caching (yet).  The whitelist is empty and the

You mean you turn off connection caching? or query caching?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

> I had an interesting problem yesterday and wanted to report it before
> spending too much time tracking it down.
> 
> I have two databases configured with postgres streaming replication
> that I was putting together with a new instance of pgpool.  I'm using
> load balancing with no caching (yet).  The whitelist is empty and the
> blacklist is ".*" (so, everything).  I had the primary configured as
> backend1 and the slave configured as backend0.  I know pgpool prefers
> it the other way around, but also that it's smart enough to figure out
> which is which; backend0 is the normal primary but we'd had a failover
> recently and haven't failed back yet.
> 
> What I saw was the queries correctly went to backend1, but the COMMIT
> went to both, causing errors that filtered up to the application.
> When I switched backend0 and backend1 in the configs everything worked
> fine.
> 
> (from the postgres logs)
> LOG:  statement: COMMIT
> WARNING:  there is no transaction in progress
> 
> (and from pgpool's logs)
> ProcessBackendResponse: kind from backend: Z
> pool_read_message_length: slot: 1 length: 5
> ReadyForQuery: transaction state:T
> pool_unset_query_in_progress: done
> pool_unset_query_in_progress: done
> ProcessBackendResponse: Ready For Query
> ProcessFrontendResponse: kind from frontend Q(51)
> pool_unset_doing_extended_query_message: done
> statement: COMMIT
> pool_set_query_in_progress: done
> send_to_where: 3 query: COMMIT
> DB node id: 1 backend pid: 18487 statement: COMMIT
> wait_for_query_response: waiting for backend 1 completing the query
> DB node id: 0 backend pid: 7692 statement: COMMIT
> wait_for_query_response: waiting for backend 0 completing the query
> pool_send_and_wait: Error or notice message from backend: : DB node
> id: 0 backend pid: 7692 statement: COMMIT message: there is no tr
> ansaction in progress
> read_kind_from_backend: read kind from 0 th backend N NUM_BACKENDS: 2
> read_kind_from_backend: read kind from 1 th backend C NUM_BACKENDS: 2
> read_kind_from_backend: 1 th kind C does not match with master or
> majority connection kind Nkind mismatch among backends. Possible last
> query was: "COMMIT" kind details are: 0[N: there is no transaction in
> progress] 1[C]
> do_child: exits with status 1 due to error
> 
> 
> It looks like find_primary_node works as intended, but for at least
> one check PRIMARY_NODE_ID isn't being tested for type stream. Before I
> spend too long wandering the code I wanted to see if this was intended
> (configurable) behavior, even though it doesn't seem to be.
> _______________________________________________
> pgpool-hackers mailing list
> pgpool-hackers at pgpool.net
> http://www.pgpool.net/mailman/listinfo/pgpool-hackers