scheduler: Revert requireCanary logic #8867
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September 10, 2020 14:59
…hicorp/nomad/pull/8691/files#diff-1801138ac4d10f2064ba6f2e434ac9b4L430-R431 . The change was intended to fix a case where a canary alloc may fail to be rescheduled if all the other allocs fail as well (e.g. if all allocs happen to be placed on a node that died). However, it introduced some unintended side-effects. Reverting the change for now and will investigate further.
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scheduler: Revert requireCanary logic
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scheduler: Revert requireCanary logic
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Revert the
requireCanarycheck introduced in https://github.com/hashicorp/nomad/pull/8691/files#diff-1801138ac4d10f2064ba6f2e434ac9b4L430-R431 .The change was intended to fix a case where a canary alloc may fail to
be rescheduled if all the other allocs fail as well (e.g. if all allocs
happen to be placed on a node that died).
However, it introduced some unintended side-effects: if all allocs of a successful deployment fail, the scheduler will place canary allocs unexpectedly if the service has a single alloc that is to be migrated. Services with multiple allocations can be affected if all allocations are to be migrated or lost at once (e.g. all happen to run on a single client that is drained).
I added a test case for the failure, and it's failing in https://app.circleci.com/pipelines/github/hashicorp/nomad/11698/workflows/e90b6ba6-aad3-484d-8042-b1dce5239e50/jobs/99179 but is green ultimately.
Reverting the change for now and will investigate further.
Fixes #8866 .