[TIL] K8S Opentelemetry operator thêm environment cho pod

// injectCommonSDKConfig adds common SDK configuration environment variables to the necessary pod
// agentIndex represents the index of the pod the needs the env vars to instrument the application.
// appIndex represents the index of the pod the will produce the telemetry.
// When the pod handling the instrumentation is the same as the pod producing the telemetry agentIndex
// and appIndex should be the same value.  This is true for dotnet, java, nodejs, and python instrumentations.
// Go requires the agent to be a different container in the pod, so the agentIndex should represent this new sidecar
// and appIndex should represent the application being instrumented.
func (i *sdkInjector) injectCommonSDKConfig
    ...
    configureExporter(otelinst.Spec.Exporter, &pod, container)
    ...

// https://github.com/open-telemetry/opentelemetry-operator/blob/af567cdfd563e8a5c7a221337c4ff5edfbdf63b9/pkg/instrumentation/exporter.go#L17
func configureExporter(exporter v1alpha1.Exporter, pod *corev1.Pod, container *corev1.Container) {
    if exporter.Endpoint != "" {
        if getIndexOfEnv(container.Env, constants.EnvOTELExporterOTLPEndpoint) == -1 {
            container.Env = append(container.Env, corev1.EnvVar{
                Name:  constants.EnvOTELExporterOTLPEndpoint,
                Value: exporter.Endpoint,
            })
        }
    }
    ...

annotations:
  instrumentation.opentelemetry.io/inject-sdk: "true"