This directory tree contains the C++ API and implementation of OpenCensus tracing.

The main entry point to tracing is the span.h file. It's a relatively short file and the comments are a reference guide to the tracing API.

For a quick use guide, look at the examples/ directory.

Also see the tracing tutorial on the OpenCensus website.

• ./ - headers that are the public API for tracing.

• exporter/ - headers that are the public API for trace exporting and in-process storage.

• examples/ - usage examples for the public API.

• internal/ - internal implementation details and tests. Do not include or rely on headers from this directory!

• propagation/ - headers that are the public API for trace propagation, using different encodings.

Span is the central unit of tracing: Traces are made of Spans.

TraceId is an opaque token that uniquely identifies a trace.

SpanId is an opaque token which uniquely identifies a span within a trace.

Sampler decides whether or not a span will be sampled for export.

SpanContext consists of TraceId, SpanId, and TraceOptions.

TraceConfig is a global that holds TraceParams.

TraceParams configures the maximum number of Annotations, Attributes, MessageEvents, and Links, as well as the currently active Sampler.

The OpenCensus data model follows the Stackdriver tracing data model.

Annotations contain a text annotation along with a set of attributes.

Attributes are a map of key/value pairs where the key is a string and value is either a string, an integer, or a bool.

Links represent connections between spans in different traces.

MessageEvents represent messages (e.g. RPCs) that were sent/received between spans.