Support JAEGER_TRACEID_128BIT env var

Signed-off-by: Yuri Shkuro <github@ysh.us>

config/config.go

@@ -40,12 +40,18 @@ type Configuration struct {
 	// Can be provided by FromEnv() via the environment variable named JAEGER_SERVICE_NAME
 	ServiceName string `yaml:"serviceName"`
 
-	// Disabled can be provided by FromEnv() via the environment variable named JAEGER_DISABLED
+	// Disabled makes the config return opentracing.NoopTracer.
+	// Value can be provided by FromEnv() via the environment variable named JAEGER_DISABLED.
 	Disabled bool `yaml:"disabled"`
 
-	// RPCMetrics can be provided by FromEnv() via the environment variable named JAEGER_RPC_METRICS
+	// RPCMetrics enables generations of RPC metrics (requires metrics factory to be provided).
+	// Value can be provided by FromEnv() via the environment variable named JAEGER_RPC_METRICS
 	RPCMetrics bool `yaml:"rpc_metrics"`
 
+	// Gen128Bit isntructs the tracer to generate 128-bit wide trace IDs, compatible with W3C Trace Context.
+	// Value can be provided by FromEnv() via the environment variable named JAEGER_TRACEID_128BIT.
+	Gen128Bit bool `yaml:"traceid_128bit"`
+
 	// Tags can be provided by FromEnv() via the environment variable named JAEGER_TAGS
 	Tags []opentracing.Tag `yaml:"tags"`
 
@@ -261,12 +267,14 @@ func (c Configuration) NewTracer(options ...Option) (opentracing.Tracer, io.Clos
 		jaeger.TracerOptions.Metrics(tracerMetrics),
 		jaeger.TracerOptions.Logger(opts.logger),
 		jaeger.TracerOptions.CustomHeaderKeys(c.Headers),
-		jaeger.TracerOptions.Gen128Bit(opts.gen128Bit),
 		jaeger.TracerOptions.PoolSpans(opts.poolSpans),
 		jaeger.TracerOptions.ZipkinSharedRPCSpan(opts.zipkinSharedRPCSpan),
 		jaeger.TracerOptions.MaxTagValueLength(opts.maxTagValueLength),
 		jaeger.TracerOptions.NoDebugFlagOnForcedSampling(opts.noDebugFlagOnForcedSampling),
 	}
+	if c.Gen128Bit || opts.gen128Bit {
+		tracerOptions = append(tracerOptions, jaeger.TracerOptions.Gen128Bit(opts.gen128Bit))
+	}
 
 	for _, tag := range opts.tags {
 		tracerOptions = append(tracerOptions, jaeger.TracerOptions.Tag(tag.Key, tag.Value))

config/config_env.go

@@ -49,6 +49,7 @@ const (
 	envPassword                            = "JAEGER_PASSWORD"
 	envAgentHost                           = "JAEGER_AGENT_HOST"
 	envAgentPort                           = "JAEGER_AGENT_PORT"
+	env128bit                              = "JAEGER_TRACEID_128BIT"
 )
 
 // FromEnv uses environment variables to set the tracer's Configuration
@@ -83,6 +84,14 @@ func (c *Configuration) FromEnv() (*Configuration, error) {
 		c.Tags = parseTags(e)
 	}
 
+	if e := os.Getenv(env128bit); e != "" {
+		if value, err := strconv.ParseBool(e); err == nil {
+			c.Gen128Bit = value
+		} else {
+			return nil, errors.Wrapf(err, "cannot parse env var %s=%s", env128bit, e)
+		}
+	}
+
 	if c.Sampler == nil {
 		c.Sampler = &SamplerConfig{}
 	}

config/config_test.go

@@ -123,6 +123,7 @@ func TestConfigFromEnv(t *testing.T) {
 	setEnv(t, envServiceName, "my-service")
 	setEnv(t, envDisabled, "false")
 	setEnv(t, envRPCMetrics, "true")
+	setEnv(t, env128bit, "true")
 	setEnv(t, envTags, "KEY=VALUE")
 
 	// test with env set
@@ -133,13 +134,15 @@ func TestConfigFromEnv(t *testing.T) {
 	assert.Equal(t, "my-service", cfg.ServiceName)
 	assert.Equal(t, false, cfg.Disabled)
 	assert.Equal(t, true, cfg.RPCMetrics)
+	assert.Equal(t, true, cfg.Gen128Bit)
 	assert.Equal(t, "KEY", cfg.Tags[0].Key)
 	assert.Equal(t, "VALUE", cfg.Tags[0].Value)
 
 	// cleanup
 	unsetEnv(t, envServiceName)
 	unsetEnv(t, envDisabled)
 	unsetEnv(t, envRPCMetrics)
+	unsetEnv(t, env128bit)
 	unsetEnv(t, envTags)
 }
 
@@ -479,6 +482,10 @@ func TestParsingErrorsFromEnv(t *testing.T) {
 			envVar: envDisabled,
 			value:  "NOT_A_BOOLEAN",
 		},
+		{
+			envVar: env128bit,
+			value:  "NOT_A_BOOLEAN",
+		},
 		{
 			envVar: envSamplerParam,
 			value:  "NOT_A_FLOAT",