[GitHub] merlimat opened a new pull request #1249: Fixed Journal static empty array list recycling

[GitBox <gi...@apache.org>]

merlimat opened a new pull request #1249: Fixed Journal static empty array list recycling
URL: https://github.com/apache/bookkeeper/pull/1249
 
 
   When `journalSyncData=false`, we passing `EMPTY_ARRAY_LIST` to the `ForceWriteThread` when the journal is rolled over. 
   
   
   I have seen this exception:
   
   ```
   18:39:52.285 [ForceWriteThread] ERROR org.apache.bookkeeper.bookie.BookieCriticalThread - Uncaught exception in thread ForceWriteThread and is exiting!
   java.lang.NullPointerException: null
   	at io.netty.util.Recycler$DefaultHandle.recycle(Recycler.java:219) ~[io.netty-netty-all-4.1.21.Final.jar:4.1.21.Final]
   	at org.apache.bookkeeper.common.collections.RecyclableArrayList.recycle(RecyclableArrayList.java:55) ~[org.apache.bookkeeper-bookkeeper-server-shaded-4.7.0-SNAPSHOT.jar:4.7.0-SNAPSHOT]
   	at org.apache.bookkeeper.bookie.Journal$ForceWriteRequest.recycle(Journal.java:402) ~[org.apache.bookkeeper-bookkeeper-server-shaded-4.7.0-SNAPSHOT.jar:4.7.0-SNAPSHOT]
   	at org.apache.bookkeeper.bookie.Journal$ForceWriteRequest.access$1(Journal.java:399) ~[org.apache.bookkeeper-bookkeeper-server-shaded-4.7.0-SNAPSHOT.jar:4.7.0-SNAPSHOT]
   	at org.apache.bookkeeper.bookie.Journal$ForceWriteThread.run(Journal.java:506) ~[org.apache.bookkeeper-bookkeeper-server-shaded-4.7.0-SNAPSHOT.jar:4.7.0-SNAPSHOT]
   ```
   
   This is due to calling `recycle()` twice on the same `EMPTY_ARRAY_LIST`  instance. The solution is that `EMPTY_ARRAY_LIST` should not be a pooled instance and we should check that before recycling.

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