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https://issues.apache.org/jira/browse/FLINK-36192?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17878735#comment-17878735
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Rui Fan commented on FLINK-36192:
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{quote}{color:#172b4d}like {color}{*}eventType='{*}{color:#172b4d}*Warning'*
{*}reason = 'scaleUp{*}{*}Limited' message = 'currently unable to scale up due
to the limit of the number of source partitions.'{*} ?{color}
{quote}
Overall LGTM, could we involve the vertex id in the message? It's useful to
distinguish which source is limited when one job has multiple sources.
> Optimize the logic to make it the common divisor of the partition number of
> the data source when determining the parallelism of the source task.
> ------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: FLINK-36192
> URL: https://issues.apache.org/jira/browse/FLINK-36192
> Project: Flink
> Issue Type: Improvement
> Components: Autoscaler
> Reporter: yuanfenghu
> Priority: Minor
>
> *Description:*
> We hope that when we know the number of partitions of Kafka data, we can try
> our best to make the parallelism of tasks that consume Kafka equal to the
> common divisor of the partitions, so that the tasks that are consumed can be
> balanced.
>
> {*}current logic{*}:
> Currently, the parallelism of tasks in the autoscaler is determined as
> follows:
> step1: Calculate the processing rate of the task target and the corresponding
> parallelism p1
> step2: Use the currently calculated degree of parallelism and the maximum
> degree of parallelism of the operator to calculate, and take out the greatest
> common divisor p2 of the maximum degree of parallelism / 2. If p2 <
> maxparalleliem / 2, use p2 as the final degree of parallelism. If p2 >
> maxparalleliem / 2 then use p1 as the final parallelism
> If the task that needs to be judged is a task that consumes Kafka or Pulsar,
> the maximum parallelism of the task will be determined first: if the number
> of partitions < the maximum parallelism of the current task, then the maximum
> parallelism of the current task is the number of partitions of Kafka or
> Pulsar. , otherwise the maximum degree of parallelism remains unchanged, so
> there are the following situations:
> When the number of partitions in kafka or pulsar is less than the maximum
> parallelism of the operator
> 1. If the parallelism calculated in step 1 <the number of kafka or pulsar
> partitions/2, then the demand is met and the number of tasks can be balanced.
> 2. If the parallelism calculated in step 1 > the number of kafka or pulsar
> partitions / 2, use the parallelism calculated in step 1. At this time, the
> consumption will become unbalanced. For example, the number of partitions in
> kafka is 64, and the expected parallelism calculated in step 1 is If the
> degree is 48, the final task parallelism degree is 48
> When the number of partitions in kafka or pulsar is greater than the maximum
> parallelism of the operator
> Calculate the parallelism completely according to the logic of step 1. For
> example, the parallelism of one of my kafka partitions is 200, and the
> maximum parallelism of the operator is 128. Then the calculated parallelism
> is 2, 4, 8, 16... It is very likely that Kafka cannot be consumed evenly
>
> {*}expect logic{*}:
> * When the number of partitions is less than the maximum parallelism,
> determine the number of parallelism of the task as the common divisor of the
> number of partitions.
> * When the number of partitions is greater than the maximum parallelism, the
> number of parallelism of the task is determined to be the common divisor of
> the number of partitions but does not exceed the maximum parallelism.
>
>
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