[pgpool-general: 8961] Re: Java application occasionally gets "The connection attempt failed" errors

[Tatsuo Ishii]

> PgPool 4.3.7 and PG 14.7
> 
> By "occasionally", I mean 1 or 2 times for every 500 "batches" of data
> we process.
> 
> Attached is the error message text, the pgpool.conf file and
> postgresql.conf file.
> 
> "ps | aux | grep <db application user name>" shows maybe a dozen
> connections to PgPool.
> 
> We do not get these errors when connecting directly to the database on
> node "a".
> 
> It's a three node cluster (named "a", "b" and "c").  The VIP is
> attached to node "c", and the PostgreSQL primary database is on node
> "a".  PG streaming replica is node "b".
> 
> Putting the VIP on node "a" does _not_ solve the problem (but it does
> make things run slower).
> 
> "num_init_children = 350" on all three nodes, and "max_connections =
> 400" on the two DB servers.
> 
> There's nothing in the error logs where PgPool "log_min_messages =
> notice" and Postgresql log_min_error_statement and log_min_messages 
> are both = info, and client_min_messages = notice.
> 
> Where else should we look?

I am not familiar with JDBC driver but it looks like JDBC driver tried
to connect to pgpool then failed. So if pgpool is related to the
problem, I guess it may worth to check parameters of pgpool.conf that
are related to connection establishment. I noticed that
serialize_accept is enabled and reserved_connections = 3, both are
different from the defaults. If you set back one of them or both to
the default, do you see any difference?

Best reagards,
--
Tatsuo Ishii
SRA OSS LLC
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp