Source: trace.go in package cloud.google.com/go/internal/trace

Copyright 2018 Google LLC 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.


package trace

import (
	"context"
	"fmt"

	"go.opencensus.io/trace"
	"google.golang.org/api/googleapi"
	"google.golang.org/genproto/googleapis/rpc/code"
	"google.golang.org/grpc/status"
)

StartSpan adds a span to the trace with the given name.

func StartSpan(ctx context.Context, name string) context.Context {
	ctx, _ = trace.StartSpan(ctx, name)
	return ctx
}

EndSpan ends a span with the given error.

func EndSpan(ctx context.Context, err error) {
	span := trace.FromContext(ctx)
	if err != nil {
		span.SetStatus(toStatus(err))
	}
	span.End()
}

toStatus interrogates an error and converts it to an appropriate OpenCensus status.

func toStatus(err error) trace.Status {
	if err2, ok := err.(*googleapi.Error); ok {
		return trace.Status{Code: httpStatusCodeToOCCode(err2.Code), Message: err2.Message}
	} else if s, ok := status.FromError(err); ok {
		return trace.Status{Code: int32(s.Code()), Message: s.Message()}
	} else {
		return trace.Status{Code: int32(code.Code_UNKNOWN), Message: err.Error()}
	}
}

TODO(deklerk): switch to using OpenCensus function when it becomes available. Reference: https://github.com/googleapis/googleapis/blob/26b634d2724ac5dd30ae0b0cbfb01f07f2e4050e/google/rpc/code.proto

func httpStatusCodeToOCCode(httpStatusCode int) int32 {
	switch httpStatusCode {
	case 200:
		return int32(code.Code_OK)
	case 499:
		return int32(code.Code_CANCELLED)
	case 500:
		return int32(code.Code_UNKNOWN) // Could also be Code_INTERNAL, Code_DATA_LOSS
	case 400:
		return int32(code.Code_INVALID_ARGUMENT) // Could also be Code_OUT_OF_RANGE
	case 504:
		return int32(code.Code_DEADLINE_EXCEEDED)
	case 404:
		return int32(code.Code_NOT_FOUND)
	case 409:
		return int32(code.Code_ALREADY_EXISTS) // Could also be Code_ABORTED
	case 403:
		return int32(code.Code_PERMISSION_DENIED)
	case 401:
		return int32(code.Code_UNAUTHENTICATED)
	case 429:
		return int32(code.Code_RESOURCE_EXHAUSTED)
	case 501:
		return int32(code.Code_UNIMPLEMENTED)
	case 503:
		return int32(code.Code_UNAVAILABLE)
	default:
		return int32(code.Code_UNKNOWN)
	}
}

TODO: (odeke-em): perhaps just pass around spans due to the cost incurred from using trace.FromContext(ctx) yet we could avoid throwing away the work done by ctx, span := trace.StartSpan.

func TracePrintf(ctx context.Context, attrMap map[string]interface{}, format string, args ...interface{}) {
	var attrs []trace.Attribute
	for k, v := range attrMap {
		var a trace.Attribute
		switch v := v.(type) {
		case string:
			a = trace.StringAttribute(k, v)
		case bool:
			a = trace.BoolAttribute(k, v)
		case int:
			a = trace.Int64Attribute(k, int64(v))
		case int64:
			a = trace.Int64Attribute(k, v)
		default:
			a = trace.StringAttribute(k, fmt.Sprintf("%#v", v))
		}
		attrs = append(attrs, a)
	}
	trace.FromContext(ctx).Annotatef(attrs, format, args...)