go.etcd.io/etcd@v3.3.27+incompatible/Documentation/dev-internal/logging.md (about) 1 --- 2 title: Logging conventions 3 --- 4 5 etcd uses the [capnslog][capnslog] library for logging application output categorized into *levels*. A log message's level is determined according to these conventions: 6 7 * Error: Data has been lost, a request has failed for a bad reason, or a required resource has been lost 8 * Examples: 9 * A failure to allocate disk space for WAL 10 11 * Warning: (Hopefully) Temporary conditions that may cause errors, but may work fine. A replica disappearing (that may reconnect) is a warning. 12 * Examples: 13 * Failure to send raft message to a remote peer 14 * Failure to receive heartbeat message within the configured election timeout 15 16 * Notice: Normal, but important (uncommon) log information. 17 * Examples: 18 * Add a new node into the cluster 19 * Add a new user into auth subsystem 20 21 * Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations. 22 * Examples: 23 * Startup configuration 24 * Start to do snapshot 25 26 * Debug: Everything is still fine, but even common operations may be logged, and less helpful but more quantity of notices. 27 * Examples: 28 * Send a normal message to a remote peer 29 * Write a log entry to disk 30 31 [capnslog]: https://github.com/coreos/pkg/tree/master/capnslog