OpenTelemetry

1. Concepts and Signals

   The signals model: traces, metrics, logs, and baggage, and how they correlate.

2. Traces and Spans

   Spans, span context, attributes, events, links, span kinds, status, and trace trees.

3. Metrics

   Counters, gauges, histograms, instruments, aggregation, and temporality.

4. Logs

   Log records, the log bridge API, and correlating logs with trace context.

5. Context Propagation and Baggage

   W3C traceparent headers, propagators, and carrying baggage across service boundaries.

6. Resources

   Resource attributes such as service.name and detection of environment metadata.

7. Instrumentation

   Manual vs automatic instrumentation and instrumentation libraries.

8. Zero-Code Instrumentation

   Agent-based auto-instrumentation for Java, Python, .NET, and Node.js.

9. Language APIs and SDKs

   The API vs SDK split, tracer and meter providers, processors, and exporters per language.

10. Semantic Conventions

    Standard attribute names for HTTP, database, messaging, RPC, and cloud telemetry.

11. Sampling

    Head and tail sampling, parent-based samplers, and sampling ratios.

12. OTLP

    OpenTelemetry Protocol over gRPC and HTTP and its encoding.

13. Collector

    Receivers, processors, exporters, pipelines, and agent vs gateway deployment.

14. Collector Configuration

    Configuring pipelines, connectors, extensions, batching, and memory limits.

15. SDK Configuration

    OTEL_* environment variables for endpoints, exporters, sampling, and resources.

16. Kubernetes and Operator

    OpenTelemetry Operator, auto-instrumentation injection, and collecting Kubernetes telemetry.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.