This document defines some terms that are used across this specification.
Some other fundamental terms are documented in the overview document.
In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even over a separate network (Wikipedia).
In OpenTelemetry we refer to in-band data as data that is passed between components of a distributed system as part of business messages, for example, when trace or correlation contexts are included in the HTTP requests in the form of HTTP headers. Such data usually does not contain the telemetry, but is used to correlate and join the telemetry produced by various components. The telemetry itself is referred to as out-of-band data: it is transmitted from applications via dedicated messages, usually asynchronously by background routines rather than from the critical path of the business logic. Metrics, logs, and traces exported to telemetry backends are examples of out-of-band data.
Denotes the library that implements the OpenTelemetry API.
See Library Guidelines and Library resource semantic conventions.
Libraries which are compatible with the Telemetry SDK and provide functionality to emit telemetry to consumers.
Denotes the library for which the telemetry signals (traces, metrics, logs) are gathered.
The calls to the OpenTelemetry API can be done either by the Instrumented Library itself, or by another Instrumentation Library.
Example: org.mongodb.client.
Denotes the library that provides the instrumentation for a given Instrumented Library. Instrumented Library and Instrumentation Library may be the same library if it has built-in OpenTelemetry instrumentation.
See Overview for a more detailed definition and naming guidelines.
Example: io.opentelemetry.contrib.mongodb.
Synonyms: Instrumenting Library.
This refers to the name and (optional) version arguments specified when
creating a new Tracer or Meter (see Obtaining a Tracer/Obtaining a Meter).
The name/version pair identifies the Instrumentation Library.
A recording of an event. Typically the record includes a timestamp indicating when the event happened as well as other data that describes what happened, where it happened, etc.
Synonyms: Log Entry.
Sometimes used to refer to a collection of Log Records. May be ambiguous, since
people also sometimes use Log to refer to a single Log Record, thus this
term should be used carefully and in the context where ambiguity is possible
additional qualifiers should be used (e.g. Log Record).
Log Records embedded inside a Span
object, in the Events list.
Log Records that are not embedded inside a Span and are recorded elsewhere.
Key/value pairs contained in a Log Record.
Logs that are recorded in a format which has a well-defined structure that allows
to differentiate between different elements of a Log Record (e.g. the Timestamp,
the Attributes, etc). The Syslog protocol (RFC 5425),
for example, defines a structured-data format.
Logs recorded in text files, often one line per log record (although multiline records are possible too). There is no common industry agreement whether logs written to text files in more structured formats (e.g. JSON files) are considered Flat File Logs or not. Where such distinction is important it is recommended to call it out specifically.