Terminology
Jaeger uses the OpenTelemetry trace data model: it receives spans over OTLP and the UI shows them with OpenTelemetry names. Jaeger’s own formats, which predate OpenTelemetry, still appear in the legacy api_v2 gRPC query service, in the Thrift and Protobuf definitions in jaeger-idl and in the storage schemas, and they use different names for some of the same concepts:
| OpenTelemetry | Legacy Jaeger formats | Notes |
|---|---|---|
| Attributes | Tags | Both support typed values, but nested tags are not supported in Jaeger. |
| Span Events | Span Logs | Point-in-time events on the span recorded in a structured form. |
| Span Links | Span References | A Jaeger Span Reference has a required type, child-of or follows-from, and always points at an earlier span. An OpenTelemetry Span Link has no type but can carry attributes. |
| Resource | Process | A description of the entity that produces the telemetry. |
Span
A span represents a logical unit of work that has an operation name, the start time of the operation, and the duration. Spans may be nested and ordered to model causal relationships.
Trace
A trace represents the data or execution path through the system. It can be thought of as a directed acyclic graph of spans.
Baggage
Baggage is arbitrary user-defined metadata (key-value pairs) that can be attached to distributed context and propagated by the tracing SDKs. See W3C Baggage for more information.
