Glossary

This glossary defines terms and concepts that are new to the OpenTelemetry project, and clarifies OpenTelemetry-specific uses of terms common in the observability field.

We also comment on spelling and capitalization when helpful. For example, see OpenTelemetry and OTel.

Terms

Aggregation

The process of combining multiple measurements into exact or estimated statistics about the measurements that took place during an interval of time, during program execution. Used by the Metric Data source.

API

Application Programming Interface. In the OpenTelemetry project, used to define how telemetry data is generated per Data source.

Application

One or more Services designed for end users or other applications.

APM

Application Performance Monitoring is about monitoring software applications, their performance (speed, reliability, availability, and so on) to detect issues, alerting and tooling for finding the root cause.

Attribute

OpenTelemetry term for Metadata. Adds key-value information to the entity producing telemetry. Used across Signals and Resources. See attribute spec.

Automatic instrumentation

Refers to telemetry collection methods that do not require the end-user to modify application’s source code. Methods vary by programming language, and examples include bytecode injection or monkey patching.

Baggage

A mechanism for propagating Metadata to help establish a causal relationship between events and services. See baggage spec.

Client library

See Instrumented library.

Client-side app

A component of an Application that is not running inside a private infrastructure and is typically used directly by end-users. Examples of client-side apps are browser apps, mobile apps, and apps running on IoT devices.

Collector

The OpenTelemetry Collector, or Collector for short, is a vendor-agnostic implementation on how to receive, process, and export telemetry data. A single binary that can be deployed as an agent or gateway.

Spelling: When referring to the OpenTelemetry Collector, always capitalize Collector. Use just “Collector” if you are using Collector as an adjective — for example, “Collector configuration”.

Contrib

Several Instrumentation Libraries and the Collector offer a set of core capabilities as well as a dedicated contrib repository for non-core capabilities including vendor Exporters.

Context propagation

Allows all Data sources to share an underlying context mechanism for storing state and accessing data across the lifespan of a Transaction. See context propagation spec.

DAG

Directed Acyclic Graph.

Data source

See Signal

Dimension

A term used specifically by Metrics. See Attribute.

Distributed tracing

Tracks the progression of a single Request, called a Trace, as it is handled by Services that make up an Application. A Distributed trace transverses process, network and security boundaries.

See Distributed tracing.

Distribution

A distribution is a wrapper around an upstream OpenTelemetry repository with some customizations. See Distributions.

Event

An Event is a Log Record with an event name and a well-known structure. For example, browser events in OpenTelemetry follow a particular naming convention and carry particular data in a common structure.

Exporter

Provides functionality to emit telemetry to consumers. Exporters can be push- or pull-based.

Field

A term used specifically by Log Records. Metadata can be added through defined fields, including Attributes and Resource. Other fields may also be considered Metadata, including severity and trace information. See the field spec.

gRPC

A high-performance, open source universal RPC framework. See gRPC.

HTTP

Short for Hypertext Transfer Protocol.

Instrumented library

Denotes the Library for which the telemetry signals (Traces, Metrics, Logs) are gathered. See Instrumented library.

Instrumentation library

Denotes the Library that provides the instrumentation for a given Instrumented library. Instrumented library and Instrumentation library can be the same Library if it has built-in OpenTelemetry instrumentation. See the lib specification.

JSON

Short for JavaScript Object Notation.

Label

A term used specifically by Metrics. See Metadata.

Language

Programming Language.

Library

A language-specific collection of behavior invoked by an interface.

Log

Sometimes used to refer to a collection of Log records. Can be ambiguous since people also sometimes use Log to refer to a single Log record. Where ambiguity is possible, use additional qualifiers, for example, Log record. See Log.

Log record

A recording of data with a timestamp and a severity. May also have a Trace ID and Span ID when correlated with a trace. See Log record.

Metadata

A key-value pair, for example foo="bar", added to an entity producing telemetry. OpenTelemetry calls these pairs Attributes. In addition, Metrics have Dimensions an Labels, while Logs have Fields.

Metric

Records a data point, either raw measurements or predefined aggregation, as time series with Metadata. See Metric.

OC

Short form for OpenCensus.

Observability backend

The component of an observability platform that is responsible for receiving, processing, storing, and querying telemetry data. Examples include open source tools like Jaeger and Prometheus, as well as commercial offerings. OpenTelemetry is not an observability backend.

Observability frontend

The component of an observability platform that provides user interfaces for visualizing and analyzing telemetry data. It can be often a part of an observability backend, particularly when considering commercial offerings.

OpAMP

Abbreviation for the Open Agent Management Protocol.

Spelling: Write OpAMP, not OPAMP nor opamp in descriptions or instructions.

OpenCensus

Precursor to OpenTelemetry. For details, see History.

OpenTelemetry

Formed through a merger of the OpenTracing and OpenCensus projects, OpenTelemetry — the subject of this website — is a collection of APIs, SDKs, and tools that you can use to instrument, generate, collect, and export telemetry data such as metrics, logs, and traces.

Spelling: OpenTelemetry should always be a single unhyphenated word and capitalized as shown.

OpenTracing

Precursor to OpenTelemetry. For details, see History.

OT

Short form for OpenTracing.

OTel

Short form for OpenTelemetry.

Spelling: Write OTel, not OTEL.

OTelCol

Short form for OpenTelemetry Collector.

OTEP

An acronym for OpenTelemetry Enhancement Proposal.

Spelling: Write “OTEPs” as plural form. Don’t write OTep or otep in descriptions.

OTLP

Short for OpenTelemetry Protocol.

Propagators

Used to serialize and deserialize specific parts of telemetry data such as span context and Baggage in Spans. See Propagators.

Proto

Language independent interface types. See opentelemetry-proto.

Receiver

The term used by the Collector to define how telemetry data is received. Receivers can be push- or pull-based. See Receiver.

Request

See Distributed Tracing.

Resource

Captures information about the entity producing telemetry as Attributes. For example, a process producing telemetry that is running in a container on Kubernetes has a process name, a pod name, a namespace, and possibly a deployment name. All these attributes can be included in the Resource.

REST

Short for Representational State Transfer.

RPC

Short for Remote Procedure Call.

Sampling

A mechanism to control the amount of data exported. Most commonly used with the Tracing Data Source. See Sampling.

SDK

Short for Software Development Kit. Refers to a telemetry SDK that denotes a Library that implement the OpenTelemetry API.

Semantic conventions

Defines standard names and values of Metadata in order to provide vendor-agnostic telemetry data.

Service

A component of an Application. Multiple instances of a Service are typically deployed for high availability and scalability. A Service can be deployed in multiple locations.

Signal

One of Traces, Metrics or Logs. See Signals.

Span

Represents a single operation within a Trace. See Span.

Span link

A span link is a link between causally-related spans. For details see Links between spans and Specifying Links.

Specification

Describes the cross-language requirements and expectations for all implementations. See Specification.

Status

The result of the operation. Typically used to indicate whether an error occurred. See Status.

Tag

See Metadata.

Trace

A DAG of Spans, where the edges between Spans are defined as parent-child relationship. See Traces.

Tracer

Responsible for creating Spans. See Tracer.

Transaction

See Distributed Tracing.

zPages

An in-process alternative to external exporters. When included, they collect and aggregate tracing and metrics information in the background; this data is served on web pages when requested. See zPages.