• Examples:
• Failure to send raft message to a remote peer

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

• Examples:
• Add a new node into the cluster
• Add a new user into auth subsystem

• 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