Module Review: Zero to Tracing

Key Takeaways

Distributed Tracing is essential for debugging latency in microservices; logs alone are insufficient.
OpenTelemetry provides a vendor-agnostic standard for generating telemetry (traces, metrics, logs).
Auto-Instrumentation allows you to add tracing to Java applications with zero code changes using the Java Agent.
Go Applications require library instrumentation (middleware) because they are compiled to machine code.
Jaeger is a popular open-source backend for visualizing traces.
Context Propagation passes Trace IDs between services (via headers) to link spans into a single trace.

What is a Span?

A span is the basic unit of work in a trace. It represents an operation (like an HTTP request) and has a start time, duration, and attributes.

What port does OTLP gRPC use?

Port 4317. (HTTP uses 4318).

How does the Java Agent work?

It uses bytecode manipulation to inject instrumentation code into classes at runtime (e.g., intercepting HTTP calls).

What environment variable sets the service name?

OTEL_SERVICE_NAME

Why do we need Context Propagation?

To pass the Trace ID from one service to the next, ensuring all spans are linked to the same trace.

Variable	Purpose	Example
`OTEL_SERVICE_NAME`	Identifies your service in Jaeger	`order-service`
`OTEL_EXPORTER_OTLP_ENDPOINT`	Where to send telemetry	`http://localhost:4317`
`OTEL_TRACES_SAMPLER`	How much data to keep	`always_on`, `parentbased_traceidratio`
`OTEL_TRACES_EXPORTER`	Which exporter to use	`otlp`, `console`, `none`
`OTEL_JAVAAGENT_DEBUG`	Verbose logs for Java Agent	`true`

Start Jaeger: docker run ... jaegertracing/all-in-one
Java Setup: Download opentelemetry-javaagent.jar and run with -javaagent:opentelemetry-javaagent.jar.
Go Setup: Install go.opentelemetry.io/contrib/... middleware and initialize a TracerProvider.
Verify: Check http://localhost:16686 for traces.