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Posted to issues@bookkeeper.apache.org by GitBox <gi...@apache.org> on 2022/02/24 03:08:08 UTC
[GitHub] [bookkeeper] shustsud edited a comment on issue #3070: checkAllLedgers gets stuck when read throttling is enabled.

shustsud edited a comment on issue #3070:
URL: https://github.com/apache/bookkeeper/issues/3070#issuecomment-1049446938


   @lordcheng10 
   
   readEntryComplete(callback) is run in the BookKeeperClientWorker-OrderedExecutor thread.
   ```
   https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L314
   ```
   
   Then, BookKeeperClientWorker-OrderedExecutor thread acquires the lock of semaphore.
   ```
   https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L323
    -> https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L430-L431
     -> https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L469
      -> https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L208
       -> https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L246
       or
       -> https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L291
   ```
   
   If all BookKeeperClientWorker-OrderedExecutor threads are waiting to acquire the lock, there are no available BookKeeperClientWorker-OrderedExecutor threads, so readEntryComplete(callback) will not be run.
   If readEntryComplete(callback) is not run, the lock on semaphore is not released, so I think checkAllLedgers gets stuck.
   ```
   https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L80-L82
   https://github.com/apache/bookkeeper/blob/525a4a03f99afe1dca120477273537a6db46873c/bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java#L314-L316
   ```
   
   If you set a low value for read throttle(inFlightReadEntryNumInLedgerChecker) and also a low value for the number of threads in BookKeeperClientWorker-OrderedExecutor(numWorkerThreads?), I think this problem will be reproduced.
   


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