etcd uses the capnslog 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
- Examples:
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
- Examples:
Notice: Normal, but important (uncommon) log information.
- Examples:
- Add a new node into the cluster
- Add a new user into auth subsystem
- Examples:
Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations.
- Examples:
- Startup configuration
- Start to do snapshot
- Examples:
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
- Examples: