OpenMetrics/Promethus telemetry

Various server statistics is provided in OpenMetrics format by "openmetrics" module.

To enable it, add following line to the server config:

openmetrics tcp://127.0.0.1:9749 { }

Scrape endpoint would be http://127.0.0.1:9749/metrics.

Metrics

# AUTH command failures due to invalid credentials.
maddy_smtp_failed_logins{module}
# Failed SMTP transaction commands (MAIL, RCPT, DATA).
maddy_smtp_failed_commands{module, command, smtp_code, smtp_enchcode}
# Messages rejected with 4xx code due to ratelimiting.
maddy_smtp_ratelimit_deferred{module}
# Amount of started SMTP trasanactions started.
maddy_smtp_started_transactions{module}
# Amount of aborted SMTP trasanactions started.
maddy_smtp_aborted_transactions{module}
# Amount of completed SMTP trasanactions.
maddy_smtp_completed_transactions{module}
# Number of times a check returned 'reject' result (may be more than processed
# messages if check does so on per-recipient basis)
maddy_check_reject{check}
# Number of times a check returned 'quarantine' result (may be more than
# processed messages if check does so on per-recipient basis).
maddy_check_quarantined{check}
# Amount of queued messages
maddy_queue_length{module, location}
# Outbound connections established with specific TLS security level
maddy_remote_conns_tls_level{module, level}
# Outbound connections established with specific MX security level
maddy_remote_conns_mx_level{module, level}