Dev.Poga

gRPC status codes

gRPC defined 18 status codes for returning different types of errors.

I think they’re a pretty good reference if you want to design clear error handling for API.

Status Codes

OK = 0

Not an error; returned on success.

CANCELLED = 1

The operation was cancelled (typically by the caller).

UNKNOWN = 2

Unknown error. An example of where this error may be returned is if a Status value received from another address space belongs to an error-space that is not known in this address space. Also errors raised by APIs that do not return enough error information may be converted to this error.

INVALID_ARGUMENT = 3,

Client specified an invalid argument. Note that this differs from FAILED_PRECONDITION. INVALID_ARGUMENT indicates arguments that are problematic regardless of the state of the system (e.g., a malformed file name).

DEADLINE_EXCEEDED = 4,

Deadline expired before operation could complete. For operations that change the state of the system, this error may be returned even if the operation has completed successfully. For example, a successful response from a server could have been delayed long enough for the deadline to expire.

NOT_FOUND = 5,

Some requested entity (e.g., file or directory) was not found.

ALREADY_EXISTS = 6,

Some entity that we attempted to create (e.g., file or directory) already exists.

PERMISSION_DENIED = 7,

The caller does not have permission to execute the specified operation. PERMISSION_DENIED must not be used for rejections caused by exhausting some resource (use RESOURCE_EXHAUSTED instead for those errors). PERMISSION_DENIED must not be used if the caller can not be identified (use UNAUTHENTICATED instead for those errors).

UNAUTHENTICATED = 16,

The request does not have valid authentication credentials for the operation.

RESOURCE_EXHAUSTED = 8,

Some resource has been exhausted, perhaps a per-user quota, or perhaps the entire file system is out of space.

FAILED_PRECONDITION = 9,

Operation was rejected because the system is not in a state required for the operation’s execution. For example, directory to be deleted may be non-empty, an rmdir operation is applied to a non-directory, etc.

A litmus test that may help a service implementor in deciding between FAILED_PRECONDITION, ABORTED, and UNAVAILABLE: 1. Use UNAVAILABLE if the client can retry just the failing call. 2. Use ABORTED if the client should retry at a higher-level (e.g., restarting a read-modify-write sequence). 3. Use FAILED_PRECONDITION if the client should not retry until the system state has been explicitly fixed. E.g., if an “rmdir” fails because the directory is non-empty, FAILED_PRECONDITION should be returned since the client should not retry unless they have first fixed up the directory by deleting files from it. 4. Use FAILED_PRECONDITION if the client performs conditional REST Get/Update/Delete on a resource and the resource on the server does not match the condition. E.g., conflicting read-modify-write on the same resource.

ABORTED = 10,

The operation was aborted, typically due to a concurrency issue like sequencer check failures, transaction aborts, etc.

See litmus test above for deciding between FAILED_PRECONDITION, ABORTED, and UNAVAILABLE.

OUT_OF_RANGE = 11,

Operation was attempted past the valid range. E.g., seeking or reading past end of file.

Unlike INVALID_ARGUMENT, this error indicates a problem that may be fixed if the system state changes. For example, a 32-bit file system will generate INVALID_ARGUMENT if asked to read at an offset that is not in the range [0,2^32-1], but it will generate OUT_OF_RANGE if asked to read from an offset past the current file size.

There is a fair bit of overlap between FAILED_PRECONDITION and OUT_OF_RANGE. We recommend using OUT_OF_RANGE (the more specific error) when it applies so that callers who are iterating through a space can easily look for an OUT_OF_RANGE error to detect when they are done.

UNIMPLEMENTED = 12,

Operation is not implemented or not supported/enabled in this service.

INTERNAL = 13,

Internal errors. Means some invariants expected by underlying System has been broken. If you see one of these errors, Something is very broken.

UNAVAILABLE = 14,

The service is currently unavailable. This is a most likely a transient condition and may be corrected by retrying with a backoff.

warning Although data MIGHT not have been transmitted when this status occurs, there is NOT A GUARANTEE that the server has not seen anything. So in general it is unsafe to retry on this status code if the call is non-idempotent.

See litmus test above for deciding between FAILED_PRECONDITION, ABORTED, and UNAVAILABLE.

DATA_LOSS = 15,

Unrecoverable data loss or corruption.


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