[ 
https://issues.apache.org/jira/browse/HDFS-15963?focusedWorklogId=580803&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-580803
 ]

ASF GitHub Bot logged work on HDFS-15963:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 12/Apr/21 07:23
            Start Date: 12/Apr/21 07:23
    Worklog Time Spent: 10m 
      Work Description: zhangshuyan0 commented on a change in pull request 
#2889:
URL: https://github.com/apache/hadoop/pull/2889#discussion_r611385242



##########
File path: 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
##########
@@ -153,16 +154,24 @@ synchronized boolean queryVolume(FsVolumeImpl volume) {
    * Execute the task sometime in the future, using ThreadPools.
    */
   synchronized void execute(String storageId, Runnable task) {
-    if (executors == null) {
-      throw new RuntimeException(
-          "AsyncLazyPersistService is already shutdown");
-    }
-    ThreadPoolExecutor executor = executors.get(storageId);
-    if (executor == null) {
-      throw new RuntimeException("Cannot find root storage volume with id " +
-          storageId + " for execution of task " + task);
-    } else {
-      executor.execute(task);
+    try {

Review comment:
       Yes, it is. But only when the task is not executed, an RuntimeException 
will be caught here. Once the task is executes the  try ... with block, all 
exceptions will be caught there.




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Issue Time Tracking
-------------------

    Worklog Id:     (was: 580803)
    Time Spent: 1.5h  (was: 1h 20m)

> Unreleased volume references cause an infinite loop
> ---------------------------------------------------
>
>                 Key: HDFS-15963
>                 URL: https://issues.apache.org/jira/browse/HDFS-15963
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>            Reporter: Shuyan Zhang
>            Assignee: Shuyan Zhang
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: HDFS-15963.001.patch, HDFS-15963.002.patch, 
> HDFS-15963.003.patch
>
>          Time Spent: 1.5h
>  Remaining Estimate: 0h
>
> When BlockSender throws an exception because the meta-data cannot be found, 
> the volume reference obtained by the thread is not released, which causes the 
> thread trying to remove the volume to wait and fall into an infinite loop.
> {code:java}
> boolean checkVolumesRemoved() {
>   Iterator<FsVolumeImpl> it = volumesBeingRemoved.iterator();
>   while (it.hasNext()) {
>     FsVolumeImpl volume = it.next();
>     if (!volume.checkClosed()) {
>       return false;
>     }
>     it.remove();
>   }
>   return true;
> }
> boolean checkClosed() {
>   // always be true.
>   if (this.reference.getReferenceCount() > 0) {
>     FsDatasetImpl.LOG.debug("The reference count for {} is {}, wait to be 0.",
>         this, reference.getReferenceCount());
>     return false;
>   }
>   return true;
> }
> {code}
> At the same time, because the thread has been holding checkDirsLock when 
> removing the volume, other threads trying to acquire the same lock will be 
> permanently blocked.
> Similar problems also occur in RamDiskAsyncLazyPersistService and 
> FsDatasetAsyncDiskService.
> This patch releases the three previously unreleased volume references.



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