Jaeger

Mon, 01 Jan 2024 00:00:00 +0000

Metrics tell you something is wrong. Logs tell you what happened on one service. Distributed tracing tells you what happened across all the services involved in a single request — where the time went, which service called which, and where a failure or latency spike originated.

Jaeger is an open source distributed tracing system originally from Uber, now a CNCF graduated project. It collects trace data from instrumented services, stores it, and provides a UI for querying and visualising traces. A trace is a tree of spans — each span represents one operation (an HTTP request, a database query, a cache lookup), with start time, duration, and metadata. Jaeger assembles the spans from all services involved in a request into a single trace and lets you follow a request from the frontend through every microservice it touched.

How it works

Services emit spans using the OpenTelemetry SDK (the modern standard) or the legacy Jaeger client libraries. Spans are sent to a Jaeger Collector, stored in a backend (Elasticsearch, Cassandra, or in-memory for development), and queried via the Jaeger UI or API.

The typical deployment in Kubernetes uses the Jaeger Operator:

kubectl apply -f https://github.com/jaegertracing/jaeger-operator/releases/latest/download/jaeger-operator.yaml

A minimal all-in-one instance (suitable for development):

apiVersion: jaegertracing.io/v1
kind: Jaeger
metadata:
 name: jaeger
spec:
 strategy: allInOne

For production, use the production strategy with a separate Collector, Query, and storage backend.

OpenTelemetry

Jaeger is increasingly used as a backend rather than as the instrumentation library. OpenTelemetry (OTel) is the standard for instrumenting applications — language SDKs, auto-instrumentation agents, and a Collector that receives, processes, and exports telemetry. OTel exports traces to Jaeger (or Tempo, Zipkin, or any OTLP-compatible backend) via the OTLP protocol. The practical consequence: instrument once with OTel, route to whichever backend fits.

In the observability stack

Jaeger covers the tracing pillar alongside Prometheus (metrics) and Loki (logs). Grafana can query Jaeger directly — a trace ID in a log line becomes a clickable link that opens the trace in Grafana’s trace explorer, connecting all three pillars in a single investigation workflow. Grafana Tempo is an alternative tracing backend that integrates more tightly with the Grafana stack, but Jaeger remains the standalone tracing solution with the longest track record.

Distributed-Tracing on Backend Engineering Strategy Tools

Jaeger

How it works

OpenTelemetry

In the observability stack

Resources