This guide is for troubleshooting gRPC implementations based on C core library (sources for most of them are living in the grpc/grpc repository).
Extra logging can be very useful for diagnosing problems. All gRPC implementations based on C core library support
the GRPC_VERBOSITY and GRPC_TRACE environment variables that can be used to increase the amount of information
that gets printed to stderr.
GRPC_VERBOSITY is used to set the minimum level of log messages printed by gRPC (supported values are DEBUG, INFO and ERROR).
GRPC_TRACE can be used to enable extra logging for some internal gRPC components. Enabling the right traces can be invaluable
for diagnosing for what is going wrong when things aren't working as intended. Possible values for GRPC_TRACE are listed in Environment Variables Overview.
Multiple traces can be enable at once (use comma as separator).
# Enable debug logs for an application
GRPC_VERBOSITY=debug ./helloworld_application_using_grpc
# Print info about invocations of low-level C core API.
# Note that trace logs of log level DEBUG won't be displayed
# as GRPC_VERBOSITY and GRPC_TRACE are 2 independent settings.
GRPC_TRACE=api ./helloworld_application_using_grpc
# Print info from 3 different tracers, including tracing logs with log level DEBUG
GRPC_VERBOSITY=debug GRPC_TRACE=tcp,http,api ./helloworld_application_using_grpc
Known limitations: GPRC_TRACE=tcp is currently not implemented for Windows (you won't see any tcp traces).
Please note that the GRPC_TRACE environment variable has nothing to do with gRPC's "tracing" feature (= tracing RPCs in microservice environment to gain insight about how requests are processed by deployment), it is merely used to enable printing of extra logs.