[pgpool-general: 8079] Re: ERROR: unable to read data from DB node 0
Bo Peng
pengbo at sraoss.co.jp
Tue Apr 12 16:50:41 JST 2022
Hello,
On Mon, 11 Apr 2022 18:29:00 +0300
"Nikolay Mastilo (HM)" <nikm71 at hotmail.com> wrote:
> Hello,
>
> We use Pgpool as load balancer and connection pool in our application
> with three database nodes cluster (Patroni as failover manager).
>
> Previously, we received such messages in the log when starting Pgpool:
>
> 2021-11-17 13:58:40: pid 19: LOG: find_primary_node_repeatedly: waiting
> for finding a primary node
> 2021-11-17 13:58:40: pid 19: ERROR: unable to read data from DB node 0
> 2021-11-17 13:58:40: pid 19: DETAIL: EOF encountered with backend
> 2021-11-17 13:58:40: pid 19: LOG: find_primary_node:
> make_persistent_db_connection_noerror failed on node 0
> 2021-11-17 13:58:40: pid 19: ERROR: unable to read data from DB node 1
> 2021-11-17 13:58:40: pid 19: DETAIL: EOF encountered with backend
>
> These messages appeared during the first 5 minutes of the Pgpool
> starting, then stopped appearing.
>
> When we set the parameter BACKEND_FLAG0 =
> ALWAYS_PRIMARY|DISALLOW_TO_FAILOVER , such messages no longer appear on
> startup.
>
> Could you explain what happened and why such messages stopped after
> setting the specified parameter value.
At startup, pgpool connects to all PostgreSQL servers
using "sr_check_user" and "sr_check_password" to find the primary node.
The timeout for finding a primary node is defined in the following parameter:
search_primary_node_timeout = 300
If you specify "ALWAYS_PRIMARY" flag to BACKEND_FLAG0,
Pgpool-II will recognize node0 as the primary and will not connect to PostgreSQL servers.
> 2021-11-17 13:58:40: pid 19: ERROR: unable to read data from DB node 0
> 2021-11-17 13:58:40: pid 19: DETAIL: EOF encountered with backend
> 2021-11-17 13:58:40: pid 19: LOG: find_primary_node:
> make_persistent_db_connection_noerror failed on node 0
> 2021-11-17 13:58:40: pid 19: ERROR: unable to read data from DB node 1
> 2021-11-17 13:58:40: pid 19: DETAIL: EOF encountered with backend
Pgpool-II fails to connect to all PostgreSQL servers.
Please check if "sr_check_user" and "sr_check_password" are set correctly.
> --
>
> Regards,
> Nikolay
>
--
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS, Inc. Japan
http://www.sraoss.co.jp/
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