Sahdev Zala d4a21b5d17 Doc: update logging convention
Update the logging convention as capnslog is replaced by zap.
2022-04-22 14:38:48 -04:00

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# Logging Conventions
etcd uses the [zap][zap] library for logging application output categorized into *levels*. A log message's level is determined according to these conventions:
* Debug: Everything is still fine, but even common operations may be logged, and less helpful but more quantity of notices. Usually not used in production.
* Examples:
* Send a normal message to a remote peer
* Write a log entry to disk
* Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations. Should rather not be logged more frequently than once per a few seconds in normal server's operation.
* Examples:
* Startup configuration
* Start to do snapshot
* 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
* Error: Data has been lost, a request has failed for a bad reason, or a required resource has been lost.
* Examples:
* Failure to allocate disk space for WAL
* Panic: Unrecoverable or unexpected error situation that requires stopping execution.
* Examples:
* Failure to create the database
* Fatal: Unrecoverable or unexpected error situation that requires immediate exit. Mostly used in the test.
* Examples:
* Failure to find the data directory
* Failure to run a test function
[zap]: https://github.com/uber-go/zap