Glossary

The OpenTelemetry project uses terminology you may or may not be familiar with. In addition, the project may define the terminology in a different way than others. This page captures terminology used in the project and what it means.

Generic Terminology

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, etc.) to detect issues, alerting and tooling for finding the root cause.

Attribute

OpenTelemetry’s word 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

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.

Also known as the OpenTelemetry Collector. More on the Collector here.

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.

More on Distributed Tracing here.

Distribution

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

Event

Something that happened where representation depends on the Data Source. For example, Spans.

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. More on gRPC here.

HTTP

Short for Hypertext Transfer Protocol.

Instrumented Library

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

Instrumentation Library

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 more.

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. 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). See more.

Log Record

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. See more.

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 more.

OC

Short form for OpenCensus.

OpenCensus

A set of libraries for various languages that allow you to collect application metrics and distributed traces, then transfer the data to a backend of your choice in real time. Precursor to OpenTelemetry. See more.

OpenTracing

Vendor-neutral APIs and instrumentation for distributed tracing. Precursor to OpenTelemetry. See more.

OT

Short form for OpenTracing.

OTel

Short form for OpenTelemetry.

OTelCol

Short form for OpenTelemetry Collector.

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 more.

Proto

Language independent interface types. See more.

Receiver

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

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 four of 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 more.

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 may be deployed in multiple locations.

Signal

One of Traces, Metrics or Logs. More on Signals here.

Span

Represents a single operation within a Trace. See more.

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 more.

Status

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

Tag

See Metadata.

Trace

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

Tracer

Responsible for creating Spans. See more.

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 more.