This is a simple exporter for various statistics relating to a Postfix server.

Features

• Examines mail queue periodically and exports postfix_mail_queue_size;

• Reads syslog entries as they happen, and exports disposition status counters (postfix_delivery_delays_count) per DSN, as well as delay summaries per DSN (postfix_delivery_delays{quantile="..."});

• Total number of SMTP connections (postfix_smtpd_connections_total) and currently-active connections (postfix_smtpd_active_connections);

• Count how many delivery attempts were received (postfix_incoming_delivery_attempts_total), split out by whether we accepted or rejected the message (status) and the exact DSN provided to the client (dsn);

• Whether or not the Postfix master process is running (postfix_up);

• Drinks from the syslog stream directly.

Deployment

The default way of rolling out this exporter is as a Docker container. For that, you'll want to setup a volume for the postfix queue (making it available in the container as /var/spool/postfix), and some env vars. You can also run it directly (via the gem), with the same env vars, and with the expectation that /var/spool/postfix is in the usual place.

If you configure the postfix-exporter to run in the same PID namespace as whatever it is that's running Postfix itself (either --pid=host or in the same NS namespace, a la k8s pods), then the postfix_up metric will be valid, otherwise it'll be random (but unlikely to be correct).

Environment Variables

• SYSLOG_SOCKET -- where to read raw syslog events from. If you're running Postfix in an isolated container, you can probably hook up /dev/log directly between containers with a bit of shenanigans, otherwise configure your syslog daemon to write out a copy of all mail facility messages to a custom socket. Alternately, if you use logstash, take a look at the syslogstash gem and container, and go forth and sin no more.