Watch handles resourceVersion wrong

[epa095]

Warning: I might have misunderstood something. Feel free to correct.

As described several places (e.g. kubernetes-client/python-base#131 (comment)
#819) one can not just use a ẁatch on a "list-functon", but one has to first do a list, get the resourceVersion from the list-call itself, and then use that in the watch.

The problem is that watch itself reapplies the provided function in an infinite loop, and if func is e.g. list_namespace (as in the example in the readme), then the correct course of action is to get the resourceVersion of that call and use it. But instead only the resourceVersions of the elements in the list is used.

[roycaihw]

/assign

[roycaihw]

I think we do extract the latest resource version from the apiserver response and use that: https://github.com/kubernetes-client/python-base/blob/a2d1024524de78b62e5f9aa72d34cb9ea9de2b97/watch/watch.py#L96

/close

[k8s-ci-robot]

@roycaihw: Closing this issue.

In response to this:

I think we do extract the latest resource version from the apiserver response and use that: https://github.com/kubernetes-client/python-base/blob/a2d1024524de78b62e5f9aa72d34cb9ea9de2b97/watch/watch.py#L96

/close

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[epa095]

I think we do extract the latest resource version from the apiserver response and use that: https://github.com/kubernetes-client/python-base/blob/a2d1024524de78b62e5f9aa72d34cb9ea9de2b97/watch/watch.py#L96

/close

@roycaihw

But that is the resource version for each of the elements in the list, not of the list itself. The resource_version exists in the response of func (at least if func is any of the functions client.list_*_object). So something like

resp = func(*args, **kwargs)
resp.get("metadata", {}).get("resourceVersion", None)

But maybe the semantics is different because watch is set to True , and then K8s does not return a (interesting) resource_version on the list itself?

[roycaihw]

The semantics is different. The apiserver responds to watch requests with a stream of watch events. See https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes:

GET /api/v1/namespaces/test/pods?watch=1&resourceVersion=10245
---
200 OK
Transfer-Encoding: chunked
Content-Type: application/json
{
  "type": "ADDED",
  "object": {"kind": "Pod", "apiVersion": "v1", "metadata": {"resourceVersion": "10596", ...}, ...}
}
{
  "type": "MODIFIED",
  "object": {"kind": "Pod", "apiVersion": "v1", "metadata": {"resourceVersion": "11020", ...}, ...}
}
...

The python client extracts the resource version from each of the watch event. If you print the line, you will see something like:

https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes