Fix flakiness in the E2E test e2e_multi_cluster_replica_set_scale_up
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MaciejKaras
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Jul 7, 2025
docker/mongodb-kubernetes-tests/tests/multicluster/multi_cluster_replica_set_scale_up.py
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MaciejKaras
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Jul 7, 2025
docker/mongodb-kubernetes-tests/tests/multicluster/multi_cluster_replica_set_scale_up.py
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MaciejKaras
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Jul 7, 2025
1. Improve comment to mention this change can be reverted once proper fix is made to the issue why this test was flaky
anandsyncs
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viveksinghggits
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fix-flakiness-e2e_multi_cluster_replica_set_scale_up
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Summary
The E2E test
e2e_multi_cluster_replica_set_scale_uphas been flaky and @lucian-tosa suggested that we should fix it. It has been failing while waiting for statefulsets (STSs) to have correct number of in case multi cluster mongoDB deployment. And the problem was sometimes after theMongoDBMultiCluster (mdbmc)resource got into running phase (that would mean all the STSs are ready), some of the STSs got into not ready state.When we see that
mdbmcresource is Running we try to make sure that STSs have correct number of replicas but because of above problem (STSs transitioning into not ready state from ready), STS didn't have the correct number of replicas and tests failed.The reason why STS was transitioning into not ready state from ready is, the pod that it was maintaining did the same, i.e., it transitioned from ready state to not ready state. After looking into it further we got to know that the pod is behaving like this because sometimes, it's readiness probe fails momentarily. And because of that the pod gets to ready and then transitioned to not ready (readiness probe failed) and then eventually becomes ready. This is documented in much more detail in the document here.
The ideal fix of the problem would be to figure out why the readiness probe fails and then fix that. But this PR has the workaround that changes the test slightly to wait for STSs to get correct number of replicas.
Jira ticket: https://jira.mongodb.org/browse/CLOUDP-329422
Proof of Work
Ran the test
e2e_multi_cluster_replica_set_scale_upmanually locally to make sure that it's passing consistently. I am not able to reproduce the flakiness now.Checklist