Log Levels

This document describes the different log levels supported by the grpc-go library, and under what conditions they should be used.


Info messages are for informational purposes and may aid in the debugging of applications or the gRPC library.


  • The name resolver received an update.
  • The balancer updated its picker.
  • Significant gRPC state is changing.

At verbosity of 0 (the default), any single info message should not be output more than once every 5 minutes under normal operation.


Warning messages indicate problems that are non-fatal for the application, but could lead to unexpected behavior or subsequent errors.


  • Resolver could not resolve target name.
  • Error received while connecting to a server.
  • Lost or corrupt connection with remote endpoint.


Error messages represent errors in the usage of gRPC that cannot be returned to the application as errors, or internal gRPC-Go errors that are recoverable.

Internal errors are detected during gRPC tests and will result in test failures.


  • Invalid arguments passed to a function that cannot return an error.
  • An internal error that cannot be returned or would be inappropriate to return to the user.


Fatal errors are severe internal errors that are unrecoverable. These lead directly to panics, and are avoided as much as possible.


  • Internal invariant was violated.
  • User attempted an action that cannot return an error gracefully, but would lead to an invalid state if performed.