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Shuffle the segments when rebalancing the table to avoid creating hotspot servers #5197

Merged
merged 1 commit into from
Mar 31, 2020
Merged

Shuffle the segments when rebalancing the table to avoid creating hotspot servers #5197

merged 1 commit into from
Mar 31, 2020

Commits on Mar 30, 2020

  1. Shuffle the segments when rebalancing the table to avoid creating hot… 

    …spot servers

When new servers are added to an existing replica-group based table
and rebalance is triggered, current behavior will assign segments
in alphabetical order, which might move only the new segments to
the new added servers. Because queries tend to query the most recent
segments, this behavior might cause new added servers to become the
hotspot servers.
To address this issue, we shuffle the segments so that old and new
segments can be balanced assigned.
We use the hash of the table name as the random seed to shuffle the
segments so that the result is deterministic.

It is a little bit tricky to write a test case for this. Since the
change is straight-forward and the existing tests already have
pretty good coverage, after manually verified the expected behavior,
no new test is added.
    @Jackie-Jiang
    Jackie-Jiang committed Mar 30, 2020
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