grpc/doc/statuscodes.md

Status codes and their use in gRPC

gRPC uses a set of well defined status codes as part of the RPC API. All RPCs started at a client return a status object composed of an integer code and a string message. The server-side can choose the status it returns for a given RPC.

The gRPC client and server-side implementations may also generate and return status on their own when errors happen.
Only a subset of the pre-defined status codes are generated by the gRPC libraries. The following table lists these codes and summarizes the situations in which they are generated, either by the client or the server-side library implementation.

Case	Code	Generated at Client or Server
Client Application cancelled the request	CANCELLED	Both
Deadline expires before server returns status	DEADLINE_EXCEEDED	Both
Method not found at server	UNIMPLEMENTED	Server
Server shutting down	UNAVAILABLE	Server
Server side application throws an exception (or does something other than returning a Status code to terminate an RPC)	UNKNOWN	Server
No response received before Deadline expires. This may occur either when the client is unable to send the request to the server or when the server fails to respond in time.	DEADLINE_EXCEEDED	Both
Some data transmitted (e.g., request metadata written to TCP connection) before connection breaks	UNAVAILABLE	Client
Could not decompress, but compression algorithm supported (Client -> Server)	INTERNAL	Server
Could not decompress, but compression algorithm supported (Server -> Client)	INTERNAL	Client
Compression mechanism used by client not supported at server	UNIMPLEMENTED	Server
Server temporarily out of resources (e.g., Flow-control resource limits reached)	RESOURCE_EXHAUSTED	Server
Flow-control protocol violation	INTERNAL	Both
Error parsing returned status	UNKNOWN	Client
Incorrect Auth metadata ( Credentials failed to get metadata, Incompatible credentials set on channel and call, Invalid host set in :authority metadata, etc.)	UNAUTHENTICATED	Both
Error parsing response proto	INTERNAL	Client
Error parsing request proto	INTERNAL	Server

The following status codes are never generated by the library:

• INVALID_ARGUMENT
• NOT_FOUND
• ALREADY_EXISTS
• FAILED_PRECONDITION
• ABORTED
• OUT_OF_RANGE
• DATA_LOSS