WHAT IS KUBERNETES SIDECAR CODE

WHAT IS KUBERNETES SIDECAR CODE

At that point, we wrote a spec for what an ideal sidecar injector would look like, dropped some code into a new repo, and the generic sidecar injector was born. We did find at least one open source project, but it didn’t fit our situation particularly well, or meet all of our needs. We looked around in the open source world to see if someone had already solved this generically, such as by providing a generic framework for sidecar injection. If the annotation was present on the pod, that meant it was a target for injection.įor example: /inject: true Each team had their own annotation namespace (sometimes more than one) and an annotation trigger. We discovered that each team was using an annotation on newly created pods to trigger the injection of one or more sidecars (some kind of initcontainers, containers, possibly volumes). debugging the same problems in Kubernetes clustersĪt that point we realized we should take a step back, and see if we could derive a common pattern.writing the same set of unit tests and integration tests and producing the same Docker image.This worked well until we realized that each of the teams was: Many of the infrastructure teams at Salesforce independently chose the Kubernetes mutating admission controller webhook model to dynamically inject sidecars in Kubernetes workloads. When Kubernetes announced the support for mutating admission controllers in 1.9 release, the sidecar pattern really became a “first-class citizen” of Kubernetes. (Our team explored this a bit in our Kubecon 2019, San Diego talk.) This allows service teams to focus on their application logic, while infrastructure teams provide reusable blocks that run alongside the application container to serve their needs.Īt Salesforce, many internal infrastructure teams have written sidecars to provide glue services such as logging, metrics, authorization, and certificate rotation for Kubernetes workloads. It also serves to decouple common infrastructure requirements from application code. It works very well in a polyglot world because you can use the same sidecar for services regardless of what language the services (or the sidecar) are written in. The sidecar model has a number of strengths that make it appealing. The sidecar also shares the same lifecycle as the main container application, being created and retired alongside the main application container. In the pattern, the sidecar is a separate container image that runs alongside the main container image (in the same Kubernetes Pod) and provides supporting features for the application. This pattern is named sidecar because it resembles a sidecar attached to a motorcycle. The adoption of Kubernetes in the cloud-native world, along with the proliferation of service mesh architectures, has popularized the sidecar pattern.

What is kubernetes sidecar