Jaeger

Jaeger exposes a JSON over HTTP API for queries: /api/services, /api/operations, /api/traces?service=X, /api/traces/{traceID}. The UI is backed by this API. Ingestion is via OTLP (recommended) or Jaeger-native Thrift UDP/HTTP. The Query API returns traces in Jaeger's JSON format. No official SDK for the Query API — direct HTTP calls. Authentication to the Query API is not built-in and must be added via a reverse proxy. The Jaeger Collector and Query services run as separate binaries.

Jaeger Query returns well-structured JSON errors for invalid trace IDs or missing services. HTTP 404 for not-found traces, 400 for malformed queries. The Query service is read-only and stateless — failure is non-destructive. Storage backend failures (Elasticsearch down) cause Query service to return 5xx. No circuit breaker or graceful degradation at the API level. Ingestion failures (Collector down) drop spans — no durable buffering in the default configuration.

Jaeger is a CNCF graduated distributed tracing system used for monitoring and troubleshooting microservice architectures. It accepts trace data via OTLP (recommended), Jaeger Thrift, or Zipkin formats, stores them in configurable backends (Elasticsearch, Cassandra, Badger), and exposes a Query API for retrieving traces and service maps. Agent relevance is moderate: agents debugging or monitoring distributed systems can query the Jaeger API for specific trace IDs, find traces by service/operation, or retrieve service dependency graphs. Jaeger must be self-hosted — no official managed cloud offering exists. Confidence is docs-derived.

Jaeger's Query API has no built-in authentication — it is designed for internal network access behind a reverse proxy or service mesh. Production deployments add OAuth2 proxy or network-level controls. Ingestion endpoints similarly lack auth by default. The Jaeger Operator for Kubernetes supports TLS and cert-manager integration. For agents, this means Jaeger Query access requires network-level security rather than API key management.

Documentation at jaegertracing.io covers architecture, deployment, and API reference. The HTTP API is described in the deployment docs and OpenAPI spec. Kubernetes operator documentation is detailed. Community support via CNCF Slack (#jaeger). The documentation assumes familiarity with distributed tracing concepts. API reference is functional but not as polished as commercial APM tools. Actively maintained as part of CNCF ecosystem.