Base Application Configuration

Environment Variables

• app: Specifies the name of the current service. For example, when deploying service-a, this value should be set to service-a.
• version: Sets the version of the current service. In this example, all services use v1 as their version number.
• upstream: Specifies the URL of the downstream service which will send request to. For example, service-a can set upstream to http://service-b:8080/, and so forth. If emitted, it will respond directly.

Port Configuration

The application listens on port 8080. Ensure that the containerPort in the Kubernetes deployment configuration is set to 8080.

Example Configuration

For service-a, the configuration should look like this:

containers:
- name: service-a
  image: addozhang/http-sample
  imagePullPolicy: Always
  ports:
    - containerPort: 8080
      env:
    - name: app
      value: "service-a"
    - name: version
      value: "v1"
    - name: upstream
      value: "http://service-b:8080/"

Application Behavior

When service-a is accessed, it forwards the request to service-b as configured in the upstream environment variable, and service-b further forwards it to service-c. Each service, while forwarding the request, appends its information (version, IP, and hostname).

You might receive response like below:

service-a(version: v1, ip: 10.42.0.75, hostname: service-a-74d6b8d9cd-n84h2) -> service-b(version: v1, ip: 10.42.0.74, hostname: service-b-859ff9bb95-7f6xf) -> service-c(version: v1, ip: 10.42.0.73, hostname: service-c-84bb4bcfcc-wkjhp)

OpenTelemetry Configuration

The application incorporates manual instrumentation using the OpenTelemetry SDK.

Environment Variables

• OTEL_EXPORTER_OTLP_ENDPOINT: This specifies the OTLP endpoint for the OpenTelemetry collector. If this variable is not set, the SDK will not be activated. For instance, use localhost:4318. It's important to note that the scheme is not required in this setting.
• OTEL_PROPAGATORS: This variable determines the propagator mode within the context. Options include tracecontext, baggage, b3, b3multi, or jaeger. Each option specifies a different propagation format for distributed tracing.