blob: a9471859187ba09c579a6a6e5d40f2d722cf0fb9 [file] [log] [blame]
* Copyright 2018-present Open Networking Foundation
* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
// File contains utility functions to support Open Tracing in conjunction with
// Enhanced Logging based on context propagation
package log
import (
jtracing ""
jcfg ""
const (
RootSpanNameKey = "op-name"
// Flag indicating whether to extract Log Fields from Span embedded in the received Context
var extractLogFieldsFromContext bool = true
// Flag indicating whether to process Span related operations; to save CPU cycles when disabled
var processSpanOperations bool = true
// Jaeger complaint Logger instance to redirect logs to Default Logger
type traceLogger struct {
logger *clogger
func (tl traceLogger) Error(msg string) {
tl.logger.Error(context.Background(), msg)
func (tl traceLogger) Infof(msg string, args ...interface{}) {
// Tracing logs should be performed only at Debug Verbosity
tl.logger.Debugf(context.Background(), msg, args...)
// This method will start the Tracing for a component using Component name injected from the Chart
// The close() method on returned Closer instance should be called in defer mode to gracefully
// terminate tracing on component shutdown
func InitTracingAndLogCorrelation(tracePublishEnabled bool, traceAgentAddress string, logCorrelationEnabled bool) (io.Closer, error) {
if !tracePublishEnabled && !logCorrelationEnabled {
defaultLogger.Info(context.Background(), "Skipping Global Tracer initialization as both Trace publish and Log correlation are configured as disabled")
extractLogFieldsFromContext = false
processSpanOperations = false
return ioutil.NopCloser(strings.NewReader("")), nil
if !logCorrelationEnabled {
defaultLogger.Info(context.Background(), "Disabling Log Fields extraction from context as configured")
extractLogFieldsFromContext = false
componentName := os.Getenv("COMPONENT_NAME")
if componentName == "" {
return nil, errors.New("Unable to retrieve PoD Component Name from Runtime env")
// Use basic configuration to start with; will extend later to support dynamic config updates
cfg := jcfg.Configuration{}
var err error
var jReporterConfig jcfg.ReporterConfig
var jReporterCfgOption jtracing.Reporter
// Attempt Trace Agent Address only if Trace Publishing is enabled; else directly use Loopback IP
if tracePublishEnabled {
jReporterConfig = jcfg.ReporterConfig{LocalAgentHostPort: traceAgentAddress, LogSpans: true}
jReporterCfgOption, err = jReporterConfig.NewReporter(componentName, jtracing.NewNullMetrics(), traceLogger{logger: defaultLogger})
if err != nil {
defaultLogger.Errorw(context.Background(), "Unable to create Reporter with given Trace Agent address",
Fields{"error": err, "address": traceAgentAddress})
// The Reporter initialization may fail due to Invalid Agent address or non-existent Agent (DNS lookup failure).
// It is essential for Tracer Instance to still start for correct Span propagation needed for log correlation.
// Thus, falback to use loopback IP for Reporter initialization before throwing back any error
tracePublishEnabled = false
if !tracePublishEnabled {
jReporterConfig.LocalAgentHostPort = ""
jReporterCfgOption, err = jReporterConfig.NewReporter(componentName, jtracing.NewNullMetrics(), traceLogger{logger: defaultLogger})
if err != nil {
return nil, errors.New("Failed to initialize Jaeger Tracing due to Reporter creation error : " + err.Error())
// To start with, we are using Constant Sampling type
samplerParam := 0 // 0: Do not publish span, 1: Publish
if tracePublishEnabled {
samplerParam = 1
jSamplerConfig := jcfg.SamplerConfig{Type: "const", Param: float64(samplerParam)}
jSamplerCfgOption, err := jSamplerConfig.NewSampler(componentName, jtracing.NewNullMetrics())
if err != nil {
return nil, errors.New("Unable to create Sampler : " + err.Error())
return cfg.InitGlobalTracer(componentName, jcfg.Reporter(jReporterCfgOption), jcfg.Sampler(jSamplerCfgOption))
// Extracts details of Execution Context as log fields from the Tracing Span injected into the
// context instance. Following log fields are extracted:
// 1. Operation Name : key as 'op-name' and value as Span operation name
// 2. Operation Id : key as 'op-id' and value as 64 bit Span Id in hex digits string
// Additionally, any tags present in Span are also extracted to use as log fields e.g. device-id.
// If no Span is found associated with context, blank slice is returned without any log fields
func ExtractContextAttributes(ctx context.Context) []interface{} {
if !extractLogFieldsFromContext {
return make([]interface{}, 0)
attrMap := make(map[string]interface{})
if ctx != nil {
if span := opentracing.SpanFromContext(ctx); span != nil {
if jspan, ok := span.(*jtracing.Span); ok {
// Add Log fields for operation identified by Root Level Span (Trace)
opId := jspan.SpanContext().TraceID().String()
opName := jspan.BaggageItem(RootSpanNameKey)
taskId := jspan.SpanContext().SpanID().String()
taskName := jspan.OperationName()
if opName == "" {
span.SetBaggageItem(RootSpanNameKey, taskName)
opName = taskName
attrMap["op-id"] = opId
attrMap["op-name"] = opName
// Add Log fields for task identified by Current Span, if it is different
// than operation
if taskId != opId {
attrMap["task-id"] = taskId
attrMap["task-name"] = taskName
for k, v := range jspan.Tags() {
// Ignore the special tags added by Jaeger, middleware (sampler.type, span.*) present in the span
if strings.HasPrefix(k, "sampler.") || strings.HasPrefix(k, "span.") || k == "component" {
attrMap[k] = v
return serializeMap(attrMap)
// Method to inject additional log fields into Span e.g. device-id
func EnrichSpan(ctx context.Context, keyAndValues ...Fields) {
span := opentracing.SpanFromContext(ctx)
if span != nil {
for _, field := range keyAndValues {
for k, v := range field {
span.SetTag(k, v)
// Method to inject Error into the Span in event of any operation failure
func MarkSpanError(ctx context.Context, err error) {
span := opentracing.SpanFromContext(ctx)
span.SetTag("error", true)
span.SetTag("err", err)
// Creates a Child Span from Parent Span embedded in passed context. Should be used before starting a new major
// operation in Synchronous or Asynchronous mode (go routine), such as following:
// 1. Start of all implemented External API methods unless using a interceptor for auto-injection of Span (Server side impl)
// 2. Just before calling an Third-Party lib which is invoking a External API (etcd, kafka)
// 3. In start of a Go Routine responsible for performing a major task involving significant duration
// 4. Any method which is suspected to be time consuming...
func CreateChildSpan(ctx context.Context, taskName string, keyAndValues ...Fields) (opentracing.Span, context.Context) {
if !processSpanOperations {
return opentracing.NoopTracer{}.StartSpan(taskName), ctx
parentSpan := opentracing.SpanFromContext(ctx)
childSpan, newCtx := opentracing.StartSpanFromContext(ctx, taskName)
if parentSpan == nil || parentSpan.BaggageItem(RootSpanNameKey) == "" {
childSpan.SetBaggageItem(RootSpanNameKey, taskName)
EnrichSpan(newCtx, keyAndValues...)
return childSpan, newCtx
// Creates a Async Child Span with Follows-From relationship from Parent Span embedded in passed context.
// Should be used only in scenarios when
// a) There is dis-continuation in execution and thus result of Child span does not affect the Parent flow at all
// b) The execution of Child Span is guaranteed to start after the completion of Parent Span
// In case of any confusion, use CreateChildSpan method
// Some situations where this method would be suitable includes Kafka Async RPC call, Propagation of Event across
// a channel etc.
func CreateAsyncSpan(ctx context.Context, taskName string, keyAndValues ...Fields) (opentracing.Span, context.Context) {
if !processSpanOperations {
return opentracing.NoopTracer{}.StartSpan(taskName), ctx
var asyncSpan opentracing.Span
var newCtx context.Context
parentSpan := opentracing.SpanFromContext(ctx)
// We should always be creating Aysnc span from a Valid parent span. If not, create a Child span instead
if parentSpan == nil {
defaultLogger.Warn(context.Background(), "Async span must be created with a Valid parent span only")
asyncSpan, newCtx = opentracing.StartSpanFromContext(ctx, taskName)
} else {
// Use Background context as the base for Follows-from case; else new span is getting both Child and FollowsFrom relationship
asyncSpan, newCtx = opentracing.StartSpanFromContext(context.Background(), taskName, opentracing.FollowsFrom(parentSpan.Context()))
if parentSpan == nil || parentSpan.BaggageItem(RootSpanNameKey) == "" {
asyncSpan.SetBaggageItem(RootSpanNameKey, taskName)
EnrichSpan(newCtx, keyAndValues...)
return asyncSpan, newCtx
// Extracts the span from Source context and injects into the supplied Target context.
// This should be used in situations wherein we are calling a time-sensitive operation (etcd update) and hence
// had a context.Background() used earlier to avoid any cancellation/timeout of operation by passed context.
// This will allow propagation of span with a different base context (and not the original context)
func WithSpanFromContext(targetCtx, sourceCtx context.Context) context.Context {
span := opentracing.SpanFromContext(sourceCtx)
return opentracing.ContextWithSpan(targetCtx, span)
// Utility method to convert log Fields into array of interfaces expected by zap logger methods
func serializeMap(fields Fields) []interface{} {
data := make([]interface{}, len(fields)*2)
i := 0
for k, v := range fields {
data[i] = k
data[i+1] = v
i = i + 2
return data