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Logging conventions

Logging level categories

etcd uses the zap library for logging application output categorized into levels. A log message’s level is determined according to these conventions:

  • Error: Data has been lost, a request has failed for a bad reason, or a required resource has been lost

    • Examples:

      • A failure to allocate disk space for WAL

  • Warning: (Hopefully) Temporary conditions that may cause errors, but may work fine. A replica disappearing (that may reconnect) is a warning.

    • Examples:

      • Failure to send raft message to a remote peer

      • Failure to receive heartbeat message within the configured election timeout

  • Notice: Normal, but important (uncommon) log information.

    • Examples:

      • Add a new node into the cluster

      • Add a new user into auth subsystem

  • Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations.

    • Examples:

      • Startup configuration

      • Start to do snapshot

  • Debug: Everything is still fine, but even common operations may be logged, and less helpful but more quantity of notices.

    • Examples:

      • Send a normal message to a remote peer

      • Write a log entry to disk

Last modified February 23, 2023: Update logging.md for 3.5+ to show zap as default. (3de08c8)