gRPC错误码 http状态码 provide your APIs in both gRPC and RESTful style at the same time

• How gRPC error codes map to HTTP status codes in the response

https://github.com/grpc-ecosystem/grpc-gateway/blob/master/runtime/errors.go#L15

package runtime

import (
	"context"
	"io"
	"net/http"

	"github.com/golang/protobuf/proto"
	"github.com/golang/protobuf/ptypes/any"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/grpclog"
	"google.golang.org/grpc/status"
)

// HTTPStatusFromCode converts a gRPC error code into the corresponding HTTP response status.
// See: https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto
func HTTPStatusFromCode(code codes.Code) int {
	switch code {
	case codes.OK:
		return http.StatusOK
	case codes.Canceled:
		return http.StatusRequestTimeout
	case codes.Unknown:
		return http.StatusInternalServerError
	case codes.InvalidArgument:
		return http.StatusBadRequest
	case codes.DeadlineExceeded:
		return http.StatusGatewayTimeout
	case codes.NotFound:
		return http.StatusNotFound
	case codes.AlreadyExists:
		return http.StatusConflict
	case codes.PermissionDenied:
		return http.StatusForbidden
	case codes.Unauthenticated:
		return http.StatusUnauthorized
	case codes.ResourceExhausted:
		return http.StatusTooManyRequests
	case codes.FailedPrecondition:
		return http.StatusPreconditionFailed
	case codes.Aborted:
		return http.StatusConflict
	case codes.OutOfRange:
		return http.StatusBadRequest
	case codes.Unimplemented:
		return http.StatusNotImplemented
	case codes.Internal:
		return http.StatusInternalServerError
	case codes.Unavailable:
		return http.StatusServiceUnavailable
	case codes.DataLoss:
		return http.StatusInternalServerError
	}

	grpclog.Infof("Unknown gRPC error code: %v", code)
	return http.StatusInternalServerError
}

var (
	// HTTPError replies to the request with the error.
	// You can set a custom function to this variable to customize error format.
	HTTPError = DefaultHTTPError
	// OtherErrorHandler handles the following error used by the gateway: StatusMethodNotAllowed StatusNotFound and StatusBadRequest
	OtherErrorHandler = DefaultOtherErrorHandler
)

type errorBody struct {
	Error   string     `protobuf:"bytes,1,name=error" json:"error"`
	// This is to make the error more compatible with users that expect errors to be Status objects:
	// https://github.com/grpc/grpc/blob/master/src/proto/grpc/status/status.proto
	// It should be the exact same message as the Error field.
	Message string     `protobuf:"bytes,1,name=message" json:"message"`
	Code    int32      `protobuf:"varint,2,name=code" json:"code"`
	Details []*any.Any `protobuf:"bytes,3,rep,name=details" json:"details,omitempty"`
}

// Make this also conform to proto.Message for builtin JSONPb Marshaler
func (e *errorBody) Reset()         { *e = errorBody{} }
func (e *errorBody) String() string { return proto.CompactTextString(e) }
func (*errorBody) ProtoMessage()    {}

// DefaultHTTPError is the default implementation of HTTPError.
// If "err" is an error from gRPC system, the function replies with the status code mapped by HTTPStatusFromCode.
// If otherwise, it replies with http.StatusInternalServerError.
//
// The response body returned by this function is a JSON object,
// which contains a member whose key is "error" and whose value is err.Error().
func DefaultHTTPError(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, _ *http.Request, err error) {
	const fallback = `{"error": "failed to marshal error message"}`

	w.Header().Del("Trailer")
	w.Header().Set("Content-Type", marshaler.ContentType())

	s, ok := status.FromError(err)
	if !ok {
		s = status.New(codes.Unknown, err.Error())
	}

	body := &errorBody{
		Error:   s.Message(),
		Message: s.Message(),
		Code:    int32(s.Code()),
		Details: s.Proto().GetDetails(),
	}

	buf, merr := marshaler.Marshal(body)
	if merr != nil {
		grpclog.Infof("Failed to marshal error message %q: %v", body, merr)
		w.WriteHeader(http.StatusInternalServerError)
		if _, err := io.WriteString(w, fallback); err != nil {
			grpclog.Infof("Failed to write response: %v", err)
		}
		return
	}

	md, ok := ServerMetadataFromContext(ctx)
	if !ok {
		grpclog.Infof("Failed to extract ServerMetadata from context")
	}

	handleForwardResponseServerMetadata(w, mux, md)
	handleForwardResponseTrailerHeader(w, md)
	st := HTTPStatusFromCode(s.Code())
	w.WriteHeader(st)
	if _, err := w.Write(buf); err != nil {
		grpclog.Infof("Failed to write response: %v", err)
	}

	handleForwardResponseTrailer(w, md)
}

// DefaultOtherErrorHandler is the default implementation of OtherErrorHandler.
// It simply writes a string representation of the given error into "w".
func DefaultOtherErrorHandler(w http.ResponseWriter, _ *http.Request, msg string, code int) {
	http.Error(w, msg, code)
}



https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto

// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.rpc;

option go_package = "google.golang.org/genproto/googleapis/rpc/code;code";
option java_multiple_files = true;
option java_outer_classname = "CodeProto";
option java_package = "com.google.rpc";
option objc_class_prefix = "RPC";


// The canonical error codes for Google APIs.
//
//
// Sometimes multiple error codes may apply.  Services should return
// the most specific error code that applies.  For example, prefer
// `OUT_OF_RANGE` over `FAILED_PRECONDITION` if both codes apply.
// Similarly prefer `NOT_FOUND` or `ALREADY_EXISTS` over `FAILED_PRECONDITION`.
enum Code {
  // Not an error; returned on success
  //
  // HTTP Mapping: 200 OK
  OK = 0;

  // The operation was cancelled, typically by the caller.
  //
  // HTTP Mapping: 499 Client Closed Request
  CANCELLED = 1;

  // Unknown error.  For example, this error may be returned when
  // 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.
  //
  // HTTP Mapping: 500 Internal Server Error
  UNKNOWN = 2;

  // The 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).
  //
  // HTTP Mapping: 400 Bad Request
  INVALID_ARGUMENT = 3;

  // The deadline expired before the 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.
  //
  // HTTP Mapping: 504 Gateway Timeout
  DEADLINE_EXCEEDED = 4;

  // Some requested entity (e.g., file or directory) was not found.
  //
  // Note to server developers: if a request is denied for an entire class
  // of users, such as gradual feature rollout or undocumented whitelist,
  // `NOT_FOUND` may be used. If a request is denied for some users within
  // a class of users, such as user-based access control, `PERMISSION_DENIED`
  // must be used.
  //
  // HTTP Mapping: 404 Not Found
  NOT_FOUND = 5;

  // The entity that a client attempted to create (e.g., file or directory)
  // already exists.
  //
  // HTTP Mapping: 409 Conflict
  ALREADY_EXISTS = 6;

  // 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). This error code does not imply the
  // request is valid or the requested entity exists or satisfies
  // other pre-conditions.
  //
  // HTTP Mapping: 403 Forbidden
  PERMISSION_DENIED = 7;

  // The request does not have valid authentication credentials for the
  // operation.
  //
  // HTTP Mapping: 401 Unauthorized
  UNAUTHENTICATED = 16;

  // Some resource has been exhausted, perhaps a per-user quota, or
  // perhaps the entire file system is out of space.
  //
  // HTTP Mapping: 429 Too Many Requests
  RESOURCE_EXHAUSTED = 8;

  // The operation was rejected because the system is not in a state
  // required for the operation's execution.  For example, the directory
  // to be deleted is non-empty, an rmdir operation is applied to
  // a non-directory, etc.
  //
  // Service implementors can use the following guidelines to decide
  // between `FAILED_PRECONDITION`, `ABORTED`, and `UNAVAILABLE`:
  //  (a) Use `UNAVAILABLE` if the client can retry just the failing call.
  //  (b) Use `ABORTED` if the client should retry at a higher level
  //      (e.g., when a client-specified test-and-set fails, indicating the
  //      client should restart a read-modify-write sequence).
  //  (c) 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
  //      the files are deleted from the directory.
  //
  // HTTP Mapping: 400 Bad Request
  FAILED_PRECONDITION = 9;

  // The operation was aborted, typically due to a concurrency issue such as
  // a sequencer check failure or transaction abort.
  //
  // See the guidelines above for deciding between `FAILED_PRECONDITION`,
  // `ABORTED`, and `UNAVAILABLE`.
  //
  // HTTP Mapping: 409 Conflict
  ABORTED = 10;

  // The 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.
  //
  // HTTP Mapping: 400 Bad Request
  OUT_OF_RANGE = 11;

  // The operation is not implemented or is not supported/enabled in this
  // service.
  //
  // HTTP Mapping: 501 Not Implemented
  UNIMPLEMENTED = 12;

  // Internal errors.  This means that some invariants expected by the
  // underlying system have been broken.  This error code is reserved
  // for serious errors.
  //
  // HTTP Mapping: 500 Internal Server Error
  INTERNAL = 13;

  // The service is currently unavailable.  This is most likely a
  // transient condition, which can be corrected by retrying with
  // a backoff.
  //
  // See the guidelines above for deciding between `FAILED_PRECONDITION`,
  // `ABORTED`, and `UNAVAILABLE`.
  //
  // HTTP Mapping: 503 Service Unavailable
  UNAVAILABLE = 14;

  // Unrecoverable data loss or corruption.
  //
  // HTTP Mapping: 500 Internal Server Error
  DATA_LOSS = 15;
}

grpc-ecosystem/grpc-gateway: gRPC to JSON proxy generator following the gRPC HTTP spec
https://github.com/grpc-ecosystem/grpc-gateway