Add SharedInformer implementation to python-client by Copilot · Pull Request #2515 · kubernetes-client/python

Copilot · 2026-02-20T18:34:38Z

Add docstring to _fire() explaining it executes handler callbacks
Fix resync not triggered when no watch events arrive: pass timeout_seconds=resync_period to Watch so the stream exits when resync is due; move resync check to after the stream loop (outside the event iteration)
Unit test test_thread_safety: add assertions verifying the cache actually holds every object written by the concurrent threads
Unit test test_watch_disruption_existing_items_fire_modified_after_relist: register ADDED/DELETED handlers; assert ADDED fires exactly once (initial list) and DELETED fires zero times when an item is present in both lists
E2e test test_cache_populated_after_start: verify the cached object's data field, not just its name
E2e test test_modified_event_and_cache_refresh: verify the cached object holds the updated data payload after a patch

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…example Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

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brendandburns · 2026-02-20T18:50:34Z

@copilot can you add support for BOOKMARK events?

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-20T18:52:57Z

@copilot can you add support for BOOKMARK events?

Done in 9c708ad. Added a BOOKMARK constant and registered it in the handlers dict so consumers can call add_event_handler(BOOKMARK, fn). When a BOOKMARK event arrives in the watch stream the informer fires the handler with the raw BOOKMARK object (which carries the updated resourceVersion). The cache is not modified — BOOKMARK events carry no object state change. Two new tests cover this: one verifies the handler is called with the bookmark object, the other confirms the cache is unaffected.

brendandburns · 2026-02-20T18:56:02Z

@copilot can you implement it so that the most recent resourceVersion is stored and used for the re-list operation?

… on 410 Gone Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-20T18:59:14Z

@copilot can you implement it so that the most recent resourceVersion is stored and used for the re-list operation?

Done in d21aa1b. SharedInformer now tracks _resource_version internally. After the initial list the RV is stored, and after each watch stream ends the Watch's latest RV (updated by every event including BOOKMARKs) is captured in finally. On reconnect the stored RV is passed directly to the next watch call — no full re-list is performed. The only exception is a 410 Gone response, which resets _resource_version to None so the next loop iteration triggers a fresh re-list. Three new tests cover: RV stored from Watch, reconnect skips re-list when RV is known, and 410 triggers re-list.

brendandburns · 2026-02-21T02:36:26Z

@copilot can you add end-to-end tests against a real cluster

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-21T02:39:22Z

@copilot can you add end-to-end tests against a real cluster

Done in 63bd3d5. Added kubernetes/e2e_test/test_informer.py with five tests that run against a real cluster (skipped automatically via base.get_e2e_configuration() when no cluster is reachable):

test_cache_populated_after_start — pre-existing ConfigMaps appear in the cache after start()
test_added_event_and_cache_entry — creating a ConfigMap fires ADDED and the object appears in the cache
test_modified_event_and_cache_refresh — patching a ConfigMap fires MODIFIED
test_deleted_event_removes_from_cache — deleting a ConfigMap fires DELETED and removes the object from the cache
test_resource_version_advances — the stored resourceVersion advances after receiving watch events

Each test uses a unique name (UUID suffix) and registers addCleanup to delete created ConfigMaps, so they are safe to run in parallel with other e2e tests.

brendandburns · 2026-02-27T16:51:41Z

@copilot can you add a test to validate that a full List call is made to the Kubernetes API server every resyncPeriod?

…list Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-27T16:55:13Z

@copilot can you add a test to validate that a full List call is made to the Kubernetes API server every resyncPeriod?

Done in 5a8fef1. Two changes were needed:

Implementation (informer.py): The resync block now calls self._initial_list() (a real list_func call to the API server) before firing MODIFIED for each cached object. Previously it only replayed locally-cached objects without contacting the server.

Test (test_informer.py — test_resync_period_triggers_full_list): Patches time.monotonic to make the elapsed time jump past resync_period=60 after the first watch event, then asserts list_func.call_count == 2 (once for the initial list, once for the resync).

brendandburns · 2026-02-28T03:26:59Z

@copilot can you look at the tests here: https://github.com/kubernetes-client/javascript/blob/main/src/cache_test.ts and here: https://github.com/kubernetes-client/java/blob/master/util/src/test/java/io/kubernetes/client/informer/impl/DefaultSharedIndexInformerWireMockTest.java and make sure that there are similar tests for the python informer? Thanks

…ires ADDED/MODIFIED/DELETED Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-28T03:33:23Z

@copilot can you look at the tests here: https://github.com/kubernetes-client/javascript/blob/main/src/cache_test.ts and here: https://github.com/kubernetes-client/java/blob/master/u...

Done in b91f278. Reviewed both reference test files and added 7 new tests plus two implementation changes:

Implementation changes (informer.py):

_initial_list now diffs the old cache against the new list: fires DELETED for items that disappeared, MODIFIED for items present in both, and ADDED for genuinely new items — matching the JS "initial list and delete after" and Java resync behavior.
Removed the now-redundant explicit MODIFIED loop from the resync block (the diff in _initial_list handles it).

New tests (analogous to reference tests):

Python test	Reference
`test_multiple_handlers_all_fire`	JS "multiple handlers"
`test_selectors_and_namespace_forwarded`	JS "namespace caching" / Java namespace pod informer
`test_watch_resource_version_passed_after_initial_list`	Java `lastSyncResourceVersion` / RV tracking
`test_non_410_api_exception_reconnects_without_relist`	Java `informerReListWatchOnWatchConflict`
`test_list_func_error_fires_error_handler`	Java `informerReListingOnListForbidden`
`test_initial_list_fires_added_for_each_item`	JS "informer with initial list"
`test_relist_after_410_fires_delete_for_removed_items`	JS "initial list and delete after"

All 33 tests pass.

brendandburns · 2026-02-28T22:10:26Z

@copilot please examine the tests here: https://github.com/kubernetes/client-go/blob/c86837f7edbe99923f3296ca925eb1adc7189b39/tools/cache/shared_informer_test.go and find any tests that are missing from this client's informer unit tests and add them. Fix the code if they don't pass.

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-02-28T22:13:53Z

@copilot please examine the tests here: https://github.com/kubernetes/client-go/blob/c86837f7edbe99923f3296ca925eb1adc7189b39/tools/cache/shared_informer_test.go and find any tests t...

Done in 25d1f12. Reviewed the client-go test file and added 5 new tests covering the scenarios we were missing:

Python test	client-go analogue
`test_same_handler_registered_twice_fires_twice`	`TestSharedInformerMultipleRegistration`
`test_remove_handler_while_running_stops_events`	`TestRemoveWhileActive`
`test_add_handler_while_running_receives_subsequent_events`	`TestAddWhileActive`
`test_concurrent_handler_registration_is_thread_safe`	`TestSharedInformerHandlerAbuse`
`test_watch_disruption_existing_items_fire_modified_after_relist`	`TestSharedInformerWatchDisruption`

The other client-go tests (TestIndexer, TestListenerResyncPeriods, TestResyncCheckPeriod, TestSharedInformerTransformer, TestStateSharedInformer) cover features that don't have a direct equivalent in this implementation (per-listener resync periods, index support, transform functions, IsStopped/HasSynced state methods). All 38 unit tests pass.

brendandburns · 2026-03-02T17:27:06Z

@aojea @roycaihw at this point I'm pretty happy with this as a starting point. Anyone else want to review it?

roycaihw · 2026-03-10T22:05:37Z

kubernetes/informer/informer.py

+            kw["field_selector"] = self._field_selector
+        return kw
+
+    def _fire(self, event_type, obj):


Please document what fire means (execute handler callbacks)

roycaihw · 2026-03-10T22:18:43Z

kubernetes/informer/informer.py

+                        self._fire(BOOKMARK, event.get("raw_object", obj))
+                    elif evt_type == ERROR:
+                        self._fire(ERROR, obj)
+                    # Periodic resync: full re-list from the API server, firing


This periodic resync is placed after a watch event. Does it mean that the resync won't be triggered, even if the time passes, if there is no new watch event for a while?

roycaihw · 2026-03-10T22:21:26Z

kubernetes/test/test_informer.py

+            t.start()
+        for t in threads:
+            t.join()
+        self.assertEqual(errors, [])


Also verify the content in the cache?

roycaihw · 2026-03-10T22:39:43Z

kubernetes/test/test_informer.py

+
+        modified = []
+        informer = SharedInformer(list_func=list_func)
+        informer.add_event_handler(MODIFIED, modified.append)


Shall we also confirm that no other handler (CREATED, etc.) was fired?

roycaihw · 2026-03-10T22:46:05Z

kubernetes/e2e_test/test_informer.py

+        self.addCleanup(inf.stop)
+
+        self._wait_in_cache(inf, "default/" + name)
+        self.assertEqual(_name_of(inf.cache.get_by_key("default/" + name)), name)


Other than the name, shall we also verify the data of the stored configmap, to ensure the cache was correctly populated?

roycaihw · 2026-03-10T22:47:23Z

kubernetes/e2e_test/test_informer.py

+            name=name, namespace="default", body={"data": {"k": "updated"}}
+        )
+        self._expect(seen, "MODIFIED/" + name)
+        self.assertIsNotNone(inf.cache.get_by_key("default/" + name))


Shall we also confirm the updated data for this modified configmap?

roycaihw · 2026-03-10T22:53:58Z

This is awesome. Thanks!

Should I tag the bot when I leave comments for it to react? Also I wonder if it supports squashing commits to clean up at some point.

brendandburns · 2026-03-11T16:32:21Z

@copilot please address code review comments.

brendandburns · 2026-03-11T16:33:14Z

@roycaihw Thanks for the review. I believe that Prow automatically squashes the commits when it merges?

k8s-ci-robot · 2026-03-11T16:37:08Z

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…ertions, e2e data checks Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

brendandburns · 2026-03-12T03:01:31Z

@roycaihw I think that all your comments were addressed, can you recheck?

Initial plan

ab86645

Copilot AI assigned Copilot and brendandburns Feb 20, 2026

Copilot started work on behalf of brendandburns February 20, 2026 18:34 View session

Add informer implementation: SharedInformer, ObjectCache, tests, and …

ef3f21c

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k8s-ci-robot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Feb 20, 2026

Copilot AI changed the title ~~[WIP] Add informer implementation to python-client~~ Add SharedInformer implementation to python-client Feb 20, 2026

Copilot AI requested a review from brendandburns February 20, 2026 18:42

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Copilot started work on behalf of brendandburns February 20, 2026 18:50 View session

Add BOOKMARK event support to SharedInformer

9c708ad

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Copilot finished work on behalf of brendandburns February 20, 2026 18:53

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Track and reuse resourceVersion across watch reconnects; re-list only…

d21aa1b

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Copilot finished work on behalf of brendandburns February 20, 2026 19:00

Copilot started work on behalf of brendandburns February 21, 2026 02:36 View session

Add e2e tests for SharedInformer against a real cluster

63bd3d5

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot started work on behalf of brendandburns February 27, 2026 16:52 View session

Resync now does a full re-list; add test_resync_period_triggers_full_…

5a8fef1

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Copilot finished work on behalf of brendandburns February 27, 2026 16:56

Copilot started work on behalf of brendandburns February 28, 2026 03:27 View session

Add 7 tests analogous to JS/Java reference tests; _initial_list now f…

b91f278

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Copilot finished work on behalf of brendandburns February 28, 2026 03:34

Copilot started work on behalf of brendandburns February 28, 2026 22:10 View session

Add 5 tests from client-go shared_informer_test.go scenarios

25d1f12

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Copilot finished work on behalf of brendandburns February 28, 2026 22:14

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roycaihw reviewed Mar 10, 2026

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