08006: connection_failure

What does it mean?

The connection between client and server could not be established or was dropped unexpectedly.

Why does it happen?

The server not running or restarting, network/firewall problems, wrong host/port, a listen_addresses setting that blocks access, an idle connection dropped by the network, or an overloaded server.

How to fix it

Check that the server is up and listening on the correct host/port (pg_isready host port). Verify listen_addresses in postgresql.conf and the access rules in pg_hba.conf. Check network/firewall and DNS settings. Review TCP keepalive and timeout settings in the connection pool. Look for crash/restart traces in the server log.