How to get notified when a pod or service or endpoints change?

Blankman_39677 0
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If I have a service, pod etc. that I can query using a selector changes its ip address, is there a way to get notified?

For example, say my application needs to have a list of ip addresses of a pod, or the ip address of a service. Since the container can go down and get recreated using kubernetes, is there a way to get notified when the containers go down and get recreated so I can then use the kubernetes API to get the latest values for the ip addresses?

This would be required for things like primary and slave databases etc.

Does kubernetes have a webhook type functionality that can be used to notify my app?

kubernetes
3 Answers

You can use watch API operations.

To watch all Endpoints objects:

GET /api/v1/namespaces/{namespace}/endpoints?watch=true

To watch a specific Endpoints object:

GET /api/v1/watch/namespaces/{namespace}/endpoints/{name}?watch=true

This creates a hanging HTTP GET request and you get notified whenever any of the watched objects changes.

See the Kubernetes API reference.

user_47471930

There is nothing out of the box. You would have to write a controller which can watch and get notified for change of a resource in kubernetes cluster ETCD store. The endpoint controller within kubernetes is an example of that because it updates the Endpoints object whenever IP of a pod behind a service changes.

Another example is ingress controllers which watches for any change in the Endpoints which holds the Pod IPs behind a service.

The watch API in the standard kubernetes client libraries is pretty efficient and widely used.

user_18394820
user_125388020
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