Changing resource partition count via Helix Rest does not work reliably about helix HOT 6 OPEN

@wmorgan6796 did you use the API create/delete resource?

For partition placement, change ResourceConfig does not work. It should be something in IdealState. You should update Ideal with the right partition number.

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I changed both the ideal state and the resource config

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@wmorgan6796 Is this cluster in normal state?

Means: 1) has a live controller
2) resource not disabled
3) cluster is not in maintenance mode
4) for WAGED rebalanced, not enough capacity for the cluster.
...

There are multiple cases can lead the partition not change. This requires some understand and debug with your controller log.

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Any update for this? @wmorgan6796

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Sorry I’ve been on leave for a bit and haven’t had time to come back to this.

but to answer the question:

Cluster was working
Cluster was not disabled, though we had disabled it before and after making the change.
Maintenance mode was not on in the cluster
There was plenty of capacity in the cluster.

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Interesting. I cannot reproduce it in my local. One possible situation could be you add/delete the same resource very close and almost same time. But the controller is busy with handling other notification.

Helix use selective update for the metadata:

1. The delete will trigger a child change for ZK.
2. The add will trigger another child change.
3. But if these two operations are close. Then controller will see the child change event and when read data from ZK, the IS already added back. So controller thinks there is no change.

Even your number of partition has been changed, from ZK PoV, it is not data change and will not trigger refresh of data.

In this case, either you can create the resource with different name like add some version to differentiate resource. Or add logic to make sure participants start dropping partitions then create the new ones with same name.

@wmorgan6796

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