zhangyue19921010 commented on a change in pull request #10524:
URL: https://github.com/apache/druid/pull/10524#discussion_r570013313
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File path: docs/development/extensions-core/kafka-ingestion.md
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@@ -146,6 +146,26 @@ A sample supervisor spec is shown below:
|`lateMessageRejectionStartDateTime`|ISO8601 DateTime|Configure tasks to
reject messages with timestamps earlier than this date time; for example if
this is set to `2016-01-01T11:00Z` and the supervisor creates a task at
*2016-01-01T12:00Z*, messages with timestamps earlier than *2016-01-01T11:00Z*
will be dropped. This may help prevent concurrency issues if your data stream
has late messages and you have multiple pipelines that need to operate on the
same segments (e.g. a realtime and a nightly batch ingestion pipeline).|no
(default == none)|
|`lateMessageRejectionPeriod`|ISO8601 Period|Configure tasks to reject
messages with timestamps earlier than this period before the task was created;
for example if this is set to `PT1H` and the supervisor creates a task at
*2016-01-01T12:00Z*, messages with timestamps earlier than *2016-01-01T11:00Z*
will be dropped. This may help prevent concurrency issues if your data stream
has late messages and you have multiple pipelines that need to operate on the
same segments (e.g. a realtime and a nightly batch ingestion pipeline). Please
note that only one of `lateMessageRejectionPeriod` or
`lateMessageRejectionStartDateTime` can be specified.|no (default == none)|
|`earlyMessageRejectionPeriod`|ISO8601 Period|Configure tasks to reject
messages with timestamps later than this period after the task reached its
taskDuration; for example if this is set to `PT1H`, the taskDuration is set to
`PT1H` and the supervisor creates a task at *2016-01-01T12:00Z*, messages with
timestamps later than *2016-01-01T14:00Z* will be dropped. **Note:** Tasks
sometimes run past their task duration, for example, in cases of supervisor
failover. Setting earlyMessageRejectionPeriod too low may cause messages to be
dropped unexpectedly whenever a task runs past its originally configured task
duration.|no (default == none)|
+|`dynamicAllocationTasksProperties`|Object|`dynamicAllocationTasksProperties`
to specify how to auto scale the number of Kafka ingest tasks based on Lag
metrics. See [Dynamic Allocation Tasks Properties](#Dynamic Allocation Tasks
Properties) for details.|no (default == null)|
+
+#### Dynamic Allocation Tasks Properties
+
+| Property | Description | Default |
+| ------------- | ------------- | ------------- |
+| `enableDynamicAllocationTasks` | whether enable this feature or not | false |
Review comment:
like I mentioned above. This is a compromise. Current algorithms is
relatively simple while can meet most scenarios.
But for extreme cases, if users don't set scale-related configs properly, it
will trigger scale action too frequently and creates lots of small segments. At
this time, the user needs to manually control taskCount and this config can
make disable/enable work more convenient.
When the algorithm is smart enough, It is better to remove this parameter.
As for default value false, I think it is the insurance to prevent users to
enable autoscaler by accident like left `"autoscalerConfig": {}` after delete
all the autoscaler related configs.
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