Kubernetes client-go: watch.Interface vs. cache.NewInformer vs. cache.NewSharedIndexInformer?

These methods differ in the level of abstraction. If a higher level abstraction fits your need, you should use it, as many lower level problems is solved for you.

Informers is a higher level of abstraction than watch that also include listers. In most use cases you should use any kind of Informer instead of lower level abstraction. An Informer internally consists of a watcher, a lister and an in-memory cache.

SharedInformers share the connection with the API server and other resources between your informers.

SharedIndexInformers add an index to your data cache, in case you work with a larger dataset.

It is recommended to use SharedInformers instead of the lower level abstractions. Instantiate new SharedInformes from the same SharedInformerFactory. Theres is an example in Kubernetes Handbook example

informerFactory := informers.NewSharedInformerFactory(clientset, time.Second*30)podInformer := informerFactory.Core().V1().Pods()serviceInformer := informerFactory.Core().V1().Services()podInformer.Informer().AddEventHandler(    // add your event handling )// add event handling for serviceInformerinformerFactory.Start(wait.NeverStop)informerFactory.WaitForCacheSync(wait.NeverStop)