How to diagnose and fix the 57P05 idle_session_timeout error code in Postgres. 

The 57P05 idle_session_timeout error code in PostgreSQL indicates that a session has been terminated because it was idle for longer than the idle_session_timeout setting allows. This setting is used to specify the maximum amount of time that a session can be idle before being automatically terminated by the server. Here are several examples of how this error might occur and how to resolve it:

  1. Exceeding the Idle Session Timeout:
    If the idle_session_timeout parameter is set to a certain value and a session remains idle (without any query activity) for longer than this duration, the server will terminate the session, resulting in the 57P05 error when the client next attempts to use it.
   -- Set the idle_session_timeout to 5 minutes
   SET idle_session_timeout = '5min';

In this example, any session that remains idle for more than 5 minutes will be terminated. To resolve this, you can:

  • Increase the idle_session_timeout setting to a higher value if the current setting is too aggressive for your workload.
  • Implement application logic to avoid long idle times or to handle reconnections gracefully if the session is terminated.
  1. Application Connection Pooling:
    Connection pooling in applications often keeps a number of database connections open and idle. If idle_session_timeout is set to a value that is too low, you might find that connections in the pool are being closed unexpectedly. To resolve this, you can either increase the idle_session_timeout or configure your connection pool to validate connections and re-establish them as needed. For example, in a connection pool configuration, you might use settings like testOnBorrow or testWhileIdle to check that a connection is still valid before lending it to an application.
  2. Default Server Configuration:
    The idle_session_timeout parameter might not be set explicitly, relying on the default server configuration. If the default is too low for your application’s usage pattern, you may encounter unexpected session terminations. To fix this, you can set the idle_session_timeout parameter in the postgresql.conf file to a value that better suits your needs:
   # postgresql.conf
   idle_session_timeout = '10min'

After making changes to postgresql.conf, you will need to reload the server configuration or restart the PostgreSQL server for the changes to take effect.

  1. Temporary Adjustment for a Session:
    You might want to temporarily adjust the idle_session_timeout for a specific session without affecting the global server setting. You can do this with the SET command within your session:
   SET idle_session_timeout = '15min';

This change will only apply to the current session and will be reset once the session ends.

When diagnosing the 57P05 idle_session_timeout error, check the PostgreSQL server logs for messages indicating that sessions have been terminated due to idle timeout. Review the current idle_session_timeout setting and consider whether it is appropriate for your application’s behavior.

For more information on the idle_session_timeout setting and how to configure it, you can refer to the PostgreSQL documentation on runtime configuration.

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