Automatic deletion of compaction config is no longer "false" by default

[lejinghu]

Please provide a detailed title (e.g. "Broker crashes when using TopN query with Bound filter" instead of just "Broker crashes").

Affected Version

31.0

Description

Issue

We noticed compaction configs for multiple tables were deleted after upgrading to Druid 31.0.

The history of the configs indicate they were removed by the coordinator:

{
"globalConfig": ...
"compactionConfig": null,
"auditInfo": {
"author": "KillCompactionConfig",
"identity": "KillCompactionConfig",
"comment": "CoordinatorDuty for automatic deletion of compaction config",
"ip": ""
},
"auditTime": ...
}

Although the documentation states "druid.coordinator.kill.compaction.on" is false by default (https://druid.apache.org/docs/latest/configuration/#metadata-management), it seems it is true by default.

Investigation

In Druid 29, the compaction kill is false by default

https://github.com/apache/druid/blob/druid-29.0.1/server/src/main/java/org/apache/druid/server/coordinator/DruidCoordinatorConfig.java

@config("druid.coordinator.kill.compaction.on")
@default("false")
public abstract boolean isCompactionKillEnabled();

But after the refactoring in Druid 31, the compaction takes the default config, which seems to be true by default

https://github.com/apache/druid/blob/druid-31.0.0/server/src/main/java/org/apache/druid/server/coordinator/config/CoordinatorKillConfigs.java

this.compactionConfigs = Configs.valueOrDefault(compactionConfigs, MetadataCleanupConfig.DEFAULT);

[cryptoe]

Oh yeah we might have changed the behaviour.
cc @kfaraz Could you please double check ?

[kfaraz]

Yes, @cryptoe , @lejinghu , the default was changed in Druid 31.
The doc update might have been missed.
I have created a PR to fix this.