informers (k8s)

Gives higher level programming interface for most common use case of watches: in memory caching and fast lookup of objects by name or other properties
basically an in-mem cache that sits between watch events and the user code
has advanced error behaviors, such as correcting for when long-running watch connections break
one of the main concepts of k8s design
preferred over polling, but creates load on the API server, each binary should only instantiate one informer per GVR
generated from a code generator and shipped as part of client-go
register handlers, and then start the shared informer factory
note: there is a lag between when the api server updates something and when the informer updates something
note: never mutate objects from informers, always deep copy