override reporter config only when agent host or port was set in env

config/config_env.go

@@ -187,20 +187,25 @@ func (rc *ReporterConfig) reporterConfigFromEnv() (*ReporterConfig, error) {
 		rc.User = user
 		rc.Password = pswd
 	} else {
+		useEnv := false
 		host := jaeger.DefaultUDPSpanServerHost
 		if e := os.Getenv(envAgentHost); e != "" {
 			host = e
+			useEnv = true
 		}
 
 		port := jaeger.DefaultUDPSpanServerPort
 		if e := os.Getenv(envAgentPort); e != "" {
 			if value, err := strconv.ParseInt(e, 10, 0); err == nil {
 				port = int(value)
+				useEnv = true
 			} else {
 				return nil, errors.Wrapf(err, "cannot parse env var %s=%s", envAgentPort, e)
 			}
 		}
-		rc.LocalAgentHostPort = fmt.Sprintf("%s:%d", host, port)
+		if useEnv || rc.LocalAgentHostPort == "" {
+			rc.LocalAgentHostPort = fmt.Sprintf("%s:%d", host, port)
+		}
 	}
 
 	return rc, nil

config/config_test.go

@@ -398,6 +398,68 @@ func TestReporterConfigFromEnv(t *testing.T) {
 	unsetEnv(t, envPassword)
 }
 
+func TestReporterAgentConfigFromEnv(t *testing.T) {
+	// prepare
+	unsetEnv(t, envEndpoint)
+	unsetEnv(t, envAgentHost)
+	unsetEnv(t, envAgentPort)
+
+	// No config and no env check
+	rc := ReporterConfig{}
+
+	// test
+	cfg, err := rc.reporterConfigFromEnv()
+	assert.NoError(t, err)
+
+	// verify
+	assert.Equal(t, "localhost:6831", cfg.LocalAgentHostPort)
+
+	// No env check
+	rc = ReporterConfig{
+		LocalAgentHostPort: "localhost01:7777",
+	}
+
+	// test
+	cfg, err = rc.reporterConfigFromEnv()
+	assert.NoError(t, err)
+
+	// verify
+	assert.Equal(t, "localhost01:7777", cfg.LocalAgentHostPort)
+
+	// Only host env check
+	setEnv(t, envAgentHost, "localhost02")
+	unsetEnv(t, envAgentPort)
+	rc = ReporterConfig{
+		LocalAgentHostPort: "localhost01:7777",
+	}
+
+	// test
+	cfg, err = rc.reporterConfigFromEnv()
+	assert.NoError(t, err)
+
+	// verify
+	assert.Equal(t, "localhost02:6831", cfg.LocalAgentHostPort)
+
+	// Only port env check
+	unsetEnv(t, envAgentHost)
+	setEnv(t, envAgentPort, "8888")
+	rc = ReporterConfig{
+		LocalAgentHostPort: "localhost01:7777",
+	}
+
+	// test
+	cfg, err = rc.reporterConfigFromEnv()
+	assert.NoError(t, err)
+
+	// verify
+	assert.Equal(t, "localhost:8888", cfg.LocalAgentHostPort)
+
+	// cleanup
+	unsetEnv(t, envEndpoint)
+	unsetEnv(t, envAgentHost)
+	unsetEnv(t, envAgentPort)
+}
+
 func TestParsingErrorsFromEnv(t *testing.T) {
 	setEnv(t, envAgentHost, "localhost") // we require this in order to test the parsing of the port