[GitHub] [hive] guptashailesh92 commented on pull request #3046: HIVE-25971: Closing the thread pool created for async cache

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guptashailesh92 commented on pull request #3046:
URL: https://github.com/apache/hive/pull/3046#issuecomment-1049512701


   In case of [CacheThreadPool](https://github.com/apache/hive/blob/7b7e8d4d7910b9b6dc2fe498a6a4228c628853c1/ql/src/java/org/apache/hadoop/hive/ql/exec/tez/ObjectCache.java#L59), keepAliveTime is set to 60 sec. So allowCoreThreadTimeOut is false only but it waits for the task in the [queue](https://github.com/openjdk/jdk/blob/a6610031e2816156fa14876457e260282a88d478/src/java.base/share/classes/java/util/concurrent/ThreadPoolExecutor.java#L1061) for keepAlivetime, if not found then it sets timedOut = true, which leds to thread being destroyed.
   For the cached thread pool, all threads are non-daemon threads, but shutdown hook is not called until all the non-daemon threads are destroyed.
   
   I had pasted logs , where I wrote a custom code, for printing shutdown hooks and I made sure its last line to execute. We can see the time difference (10 sec) between shutdown hook being called and last line code. The time difference can be upto 1 min. I have observed till 45 secs.
   ```
   2022-02-03 16:47:54,432 [INFO] [main] |util.Debug|: Hook: class org.apache.hadoop.hive.ql.exec.tez.ObjectCache$2 
   2022-02-03 16:48:04,079 [DEBUG] [Thread-4] |util.ShutdownHookManager|: Completed shutdown in 0.001 seconds; Timeouts: 0 
   2022-02-03 16:48:04,088 [DEBUG] [Thread-4] |util.ShutdownHookManager|: ShutdownHookManger completed shutdown.
   ```
   
   
   
   
   


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