[pgpool-hackers: 93] Re: "COMMIT" sent to read-only slave in streaming replication

Tatsuo Ishii ishii at postgresql.org
Fri Jul 20 08:02:01 JST 2012


Ok. Do you know the way to reproduce the problem reliably?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

> I meant I turned off query caching; I'm still using connection
> caching.  This is pgpool-II version 3.2alpha1 (hatsuiboshi).
> 
> 
>   alex
> 
> 
> On 7/19/12 3:00 PM, Tatsuo Ishii wrote:
>> 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
> 


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