[Flink] Support withShard read of Flink #5650
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@JingsongLi Hi, please CC, Thx. |
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Purpose
In my company, we use Flink session cluster read paimon for OLAP.
When the QPS of search is high, many problems are gradually becoming apparent.
1、The JobManager's IO is high. Because all job's plan will read meta on FileSystem.
2、To accelerate queries, when we scale-up
scan.manifest.parallelism, the memory of JobManager is high.3、The query speed become slow. Because when QPS is high, the JobManager is busy, this will reduce the speed of the plan or other logic.
4、When QPS is high, the memory is heavy, even though we DropStats after plan.
We found the reason is all job's plan is run on JobManager. In order for the system can accept higher QPS and the query speed can be faster, we we want add an option that user can move the plan to TaskManager.
Be more detailed, when open the option, ShardStaticFileStoreSource will create as many splits as source parallelism, this splits will be assigned to reader. In ShardSourceReader#addSplits we use TableScan withShard feature to get the splits that belong to this reader.
When DynamicPartitionPruning enabled, we add the DynamicPartitionPruning info into MockSplit, after reader receive it, reader will filter partitions after plan withShard.
Tests
1、UT cases
org.apache.paimon.flink.source.shardread.ShardReadAssignModeTest
org.apache.paimon.flink.source.shardread.ShardSourceReaderTest
2、IT cases
org.apache.paimon.flink.source.shardread.ShardReadITCase
3、Job Test
We run some jobs to test data integrity. The result is no problem.
(1) Without ShardRead
(2)ShardRead Without Failover Without Speculation Execution.
(3) ShardRead Without Failover with Speculation Execution.
(4)ShardRead With Failover Without Speculation Execution.
(5) ShardRead With Failover With Speculation Execution.
API and Format
Documentation