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https://issues.apache.org/jira/browse/KYLIN-1872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15372668#comment-15372668
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Ma Gang commented on KYLIN-1872:
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Read the hbase 0.98 coprocessor code, looks like interrupting rpc thread is ok,
but the rpc response from region server still goes to client side, and dropped
immediately. The only benefit to do this is it can release the hbase rpc thread
earlier.
Another option is do not interrupt the rpc thread, just mark the query is
stopped, and before adding the response to queue, if the query is stopped,
throw exception and the response is then dropped.
> Make query visible and interruptible, improve server's stablility
> -----------------------------------------------------------------
>
> Key: KYLIN-1872
> URL: https://issues.apache.org/jira/browse/KYLIN-1872
> Project: Kylin
> Issue Type: Improvement
> Components: Query Engine
> Reporter: Ma Gang
> Assignee: Ma Gang
> Attachments: query_visible_interruptable-1.4rc.patch
>
>
> Problem:
> 1. Large query result will break kylin server, for example: select * from
> fact_table. Even when properties "kylin.query.scan.threshold" and
> "kylin.query.mem.budget" are set properly, OOM still happens, because the
> hbase rpc thread is not interrupted, the result will continually go to kylin
> server. And server will run OOM quickly when there are multiple such queries.
> 2. Tow many slow queries will occupy all tomcat threads, and make server
> unresponsed.
> 3. There's no corelation id for a specified query, so it is hard to find the
> rpc log for a specified query, if there are too many queries running
> concurrently.
> Solution:
> 1. Interrupt the rpc thread and main query thread when return result size
> larger than the config limit size.
> 2. Make query visible. Admin can view all running queries, and detail of each
> query.
> Split the query into following steps:
> 1) sql parse
> 2) cube plan
> 3) query cache
> 4) multiple cube segment query
> a. for each segment request, have muliple endpoint range request.
> b. for each endpoint range request, have multiple coprocessor request.
> c. for each coprocessor request, have multiple region server rpc.
> Admin can view the startTime/endTime of each step, and the thread stack
> trace if the step is running.
> 3. Add query id as corelation id in the rpc log.
> 4. Admin can interrupt a running query, to release the thread, memory, etc.
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