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Disk decider respect watermarks for single data node #55805

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henningandersen
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@henningandersen henningandersen commented Apr 27, 2020

The disk decider had special handling for the single data node case,
allowing any allocation (skipping watermark checks) for such clusters.
This special handling can now be avoided via a setting.

I did not add to log a deprecation warning since:

  1. We should only warn if there is one data node.
  2. A cluster can temporarily have a single data node (for instance if it has 2 data nodes, but one is rolling restarted - or just during a full restart).
  3. Logging it in earlyTerminate in debug mode only, affects a variety of tests.
  4. Hopefully the majority of clusters this affects are non-production.

Will follow-up with a PR to flip the default and add breaking changes documentation for 8.0

The disk decider had special handling for the single data node case,
allowing any allocation (skipping watermark checks) for such clusters.
This special handling can now be avoided via a setting.
@henningandersen henningandersen added >enhancement :Distributed Coordination/Allocation All issues relating to the decision making around placing a shard (both master logic & on the nodes) v8.0.0 v7.8.0 labels Apr 27, 2020
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Pinging @elastic/es-distributed (:Distributed/Allocation)

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@jasontedor jasontedor left a comment

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LGTM. We'll need to follow up in Cloud to deploy with this setting set to true.

@henningandersen henningandersen merged commit 0bd28ae into elastic:master Apr 28, 2020
henningandersen added a commit to henningandersen/elasticsearch that referenced this pull request Apr 28, 2020
The disk decider had special handling for the single data node case,
allowing any allocation (skipping watermark checks) for such clusters.
This special handling can now be avoided via a setting.
henningandersen added a commit that referenced this pull request Apr 28, 2020
The disk decider had special handling for the single data node case,
allowing any allocation (skipping watermark checks) for such clusters.
This special handling can now be avoided via a setting.
@Leaf-Lin
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Leaf-Lin commented Jul 7, 2020

@henningandersen , does this apply to the single hot-data node cluster? They might have more than one data node, but only one hot-data-node allowing indexing while having other warm/cold data node for storage?

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@Leaf-Lin It only applies if there is exactly one data node.

henningandersen added a commit to henningandersen/elasticsearch that referenced this pull request Jun 3, 2021
In elastic#55805, we added a setting to allow single data node clusters to
respect the high watermark. This commit adds deprecation warnings to 7.x
to ensure we can make only true valid in 8.0.
henningandersen added a commit to henningandersen/elasticsearch that referenced this pull request Jun 3, 2021
In elastic#55805, we added a setting to allow single data node clusters to
respect the high watermark. In elastic#73733 we added the related deprecations.
This commit ensures the only valid value for the setting is true and
adds deprecations if the setting is set. The setting will be removed
in a future release.
henningandersen added a commit that referenced this pull request Jun 7, 2021
In #55805, we added a setting to allow single data node clusters to
respect the high watermark. This commit adds deprecation warnings to 7.x
to ensure we can make only true valid in 8.0.

Co-authored-by: David Turner <[email protected]>
henningandersen added a commit that referenced this pull request Jun 7, 2021
In #55805, we added a setting to allow single data node clusters to
respect the high watermark. In #73733 we added the related deprecations.
This commit ensures the only valid value for the setting is true and
adds deprecations if the setting is set. The setting will be removed
in a future release.

Co-authored-by: David Turner <[email protected]>
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5 participants