This document defines the various terms needed to understand the documentation and set up and use KEDA.

Admission Webhook

In Kubernetes, an HTTP callback that handle admission requests. KEDA uses an admission webhook to validate and mutate ScaledObject resources.

Agent

A primary role held by the KEDA operator. The Agent activates and deactivates Kubernetes Deployments to scale to and from zero.

Cluster

In Kubernetes, a set of one or more nodes that run containerized applications.

CRD

Custom Resource Definition. In Kubernetes, a custom resource that extends the Kubernetes API with custom resources like ScaledObjects that have custom fields and behavior.

Event

A notable occurrence captured by an event source that KEDA may use as a trigger to scale a container or deployment.

Event Source

An external system like Kafka, RabbitMQ, that generates events that KEDA can monitor using a scaler.

Grafana

An open-source monitoring platform that can visualize metrics collected by KEDA.

gRPC Remote Procedure Calls (gRPC)

gRPC Remote Procedure Calls (gRPC). An open-source remote procedure call framework used by KEDA components to communicate.

HPA

Horizontal Pod Autoscaler. Kubernetes autoscaler. By default, scales based on CPU/memory usage. KEDA uses HPA to scale Kubernetes clusters and deployments.

KEDA

Kubernetes Event-Driven Autoscaling. A single-purpose, lightweight autoscaler that can scale a Kubernetes workload based on event metrics.

Metric

Measurement of an event source such as queue length or response lag that KEDA uses to determine scaling.

OpenTelemetry

An observability framework used by KEDA to instrument applications and collect metrics.

Operator

The core KEDA component that monitors metrics and scales workloads accordingly.

Prometheus

An open-source monitoring system that can scrape and store metrics from KEDA.

Scaled Object

A custom resource that defines how KEDA should scale a workload based on events.

Scaled Job

A custom resource KEDA uses to scale an application.

Scaler

A component that integrates KEDA with a specific event source to collect metrics.

Stateful Set

A Kubernetes workload with persistent data. KEDA can scale stateful sets.

TLS

Transport Layer Security. KEDA uses TLS to encrypt communications between KEDA components.

Webhook

An HTTP callback used to notify KEDA of events from external sources.

In Kubernetes, an HTTP callback used as an event notification mechanism.