Sidecar Container - CI/CD Glossary Definition
A sidecar container is a helper container that runs alongside the main application container in the same Kubernetes pod, sharing its network and (optionally) volumes. Common sidecars proxy traffic, ship logs, or sync config.
How it works
Because containers in a pod share a network namespace, a sidecar can reach the main container over localhost. Service-mesh proxies (Envoy) and log shippers are typical sidecars. Kubernetes 1.28+ supports native sidecar containers via initContainers with restartPolicy: Always.
CI analog
GitHub Actions service containers play a similar role in CI: a Postgres or Redis container runs next to the job so tests can reach a real dependency.
Related guides
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Pod - CI/CD Glossary DefinitionPod: A pod is the smallest deployable unit in Kubernetes: one or more containers that share a network namespa…
Service Mesh - CI/CD Glossary DefinitionA service mesh is a layer of sidecar proxies that handles service-to-service traffic - routing, retries, mTLS…