Kubernetes provides Webhooks as a way to interact with all system generated events. This is the equivalent of http handlers and modules in ASP. Net in terms of functionality to intercept and change requests and Responses. The webhooks however are an opportunity to work on System generated resources such as pod creation requests and so on.
There are two stages where webhooks can be run. They are correspondingly named as mutating or validating webhooks. The first is an opportunity to change the requests on Kubernetes core V1 resources. The second is an opportunity to add validations to requests and Responses.
Since these span a lot of system calls the webhooks are invoked frequently. Therefore they must be selective in the requests they modify to exclude the possibility that they touch requests that were not intended.
In addition to selectors, the power of webhooks is best denomonstrated when they select all requests of a particular type to modify. For example this is an opportunity for security to raise the baseline by allowing or denying all resources of a particular kind. The execution of privileged pods may be disabled in the cluster with the help of webhooks.
The webhooks are light to run and serve similar to nginx http parameter modifiers. A number of them may be allowed to run