From ad9b6e8d814d328d6fc29f283f5ad39b9d60f627 Mon Sep 17 00:00:00 2001
From: Michael Stack <saintstack@users.noreply.github.com>
Date: Wed, 25 May 2022 16:35:56 -0700
Subject: [PATCH] =?UTF-8?q?HDFS-16586.=20Purge=20FsDatasetAsyncDiskService?=
 =?UTF-8?q?=20threadgroup;=20it=20causes=20BP=E2=80=A6=20(#4348)?=
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Remove the ThreadGroup used by executor factories; they are unused
and ThreadGroups auto-destroy when their Thread-member count goes to zero.
This behavior is incompatible with the configuration we have on the per-volume
executor which is set to let all threads die if no use inside the
keepalive time.
---
 .../datanode/fsdataset/impl/FsDatasetAsyncDiskService.java    | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
index aa577a4d2a1..9e4ce26a950 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
@@ -73,7 +73,6 @@ class FsDatasetAsyncDiskService {
   
   private final DataNode datanode;
   private final FsDatasetImpl fsdatasetImpl;
-  private final ThreadGroup threadGroup;
   private Map<String, ThreadPoolExecutor> executors
       = new HashMap<String, ThreadPoolExecutor>();
   private Map<String, Set<Long>> deletedBlockIds 
@@ -91,7 +90,6 @@ class FsDatasetAsyncDiskService {
   FsDatasetAsyncDiskService(DataNode datanode, FsDatasetImpl fsdatasetImpl) {
     this.datanode = datanode;
     this.fsdatasetImpl = fsdatasetImpl;
-    this.threadGroup = new ThreadGroup(getClass().getSimpleName());
     maxNumThreadsPerVolume = datanode.getConf().getInt(
       DFSConfigKeys.DFS_DATANODE_FSDATASETASYNCDISK_MAX_THREADS_PER_VOLUME_KEY,
           DFSConfigKeys.DFS_DATANODE_FSDATASETASYNCDISK_MAX_THREADS_PER_VOLUME_DEFAULT);
@@ -110,7 +108,7 @@ class FsDatasetAsyncDiskService {
         synchronized (this) {
           thisIndex = counter++;
         }
-        Thread t = new Thread(threadGroup, r);
+        Thread t = new Thread(r);
         t.setName("Async disk worker #" + thisIndex +
             " for volume " + volume);
         return t;