Resource Watches in Kubernetes are a powerful feature that allows for real-time updates on Kubernetes resources. Here are the possible options for implementing watches and examples for each option, along with the relevant sources:
- Start a watch at the most recent resource version: This is the recommended way to start a watch, as it ensures that the client receives the most up-to-date state of the resource. Here’s an example from the Kubernetes API Concepts documentation:
GET /api/v1/namespaces/default/pods?watch=true
Source: https://kubernetes.io/docs/reference/using-api/api-concepts
- Start a watch at any resource version: This option allows the client to start a watch at any version of the resource. However, this may result in the client receiving older, stale data. Here’s an example from the Kubernetes API Concepts documentation:
GET /api/v1/namespaces/default/pods?watch=true&resourceVersion=123
Source: https://kubernetes.io/docs/reference/using-api/api-concepts
- Use Compose Watch: Docker Compose allows for automatic service updates based on local file changes. Here’s an example from the Docker Compose Watch documentation:
services:
web:
image: my-web-image
volumes:
- .:/code
- /code/node_modules
watch:
- ./:/code
- /code/node_modules
Source: https://docs.docker.com/compose/file-watch
- Use the Karmada API: Karmada is a Kubernetes management platform that allows for watching resources. Here’s an example from the Karmada documentation:
GET /api/v1/namespaces/default/pods?watch=true&resourceVersionMatch=NotOlderThan
Source: https://karmada.io/docs/next/reference/karmada-api/common-parameter/common-parameters
- Use the etcd API: etcd is a distributed key-value store that is used by Kubernetes for storing configuration data. Here’s an example from the etcd API documentation:
GET /v3/watch/mykey
Source: https://etcd.io/docs/v3.6/learning/api
- Use the Consul API: Consul is a service mesh platform that allows for watching resources. Here’s an example from the Consul documentation:
GET /v1/watch/kv
Source: https://developer.hashicorp.com/consul/docs/dynamic-app-config/watches
- Use the Kubernetes Operator SDK: The Operator SDK allows for building Kubernetes operators that can watch resources. Here’s an example from the Operator SDK documentation:
c.Watch(&source.Kind{Type: &examplev1.Wordpress{}}, &handler.EnqueueRequestForObject{})
Source: https://sdk.operatorframework.io/docs/building-operators/golang/quickstart/
These are some of the possible options for implementing watches in Kubernetes. The choice of which option to use depends on the specific use case and the programming language being used.
