HBASE-28224 ClientSideRegionScanner appears not to shutdown MobFileCache (#5578)

Signed-off-by: Duo Zhang <zhangduo@apache.org>
(cherry picked from commit 5201ae2)

Author: jbewing

hbase-server/src/main/java/org/apache/hadoop/hbase/client/ClientSideRegionScanner.java

@@ -27,6 +27,7 @@
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.PrivateCellUtil;
 import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
+import org.apache.hadoop.hbase.io.hfile.BlockCache;
 import org.apache.hadoop.hbase.io.hfile.BlockCacheFactory;
 import org.apache.hadoop.hbase.mob.MobFileCache;
 import org.apache.hadoop.hbase.regionserver.HRegion;
@@ -46,6 +47,8 @@ public class ClientSideRegionScanner extends AbstractClientScanner {
   private static final Logger LOG = LoggerFactory.getLogger(ClientSideRegionScanner.class);
 
   private HRegion region;
+  private MobFileCache mobFileCache;
+  private BlockCache blockCache;
   RegionScanner scanner;
   List<Cell> values;
   boolean hasMore = true;
@@ -69,12 +72,14 @@ public ClientSideRegionScanner(Configuration conf, FileSystem fs, Path rootDir,
       String.valueOf(HConstants.HBASE_CLIENT_SCANNER_ONHEAP_BLOCK_CACHE_FIXED_SIZE_DEFAULT));
     // don't allow L2 bucket cache for non RS process to avoid unexpected disk usage.
     conf.unset(HConstants.BUCKET_CACHE_IOENGINE_KEY);
-    region.setBlockCache(BlockCacheFactory.createBlockCache(conf));
+    blockCache = BlockCacheFactory.createBlockCache(conf);
+    region.setBlockCache(blockCache);
     // we won't initialize the MobFileCache when not running in RS process. so provided an
     // initialized cache. Consider the case: an CF was set from an mob to non-mob. if we only
     // initialize cache for MOB region, NPE from HMobStore will still happen. So Initialize the
     // cache for every region although it may hasn't any mob CF, BTW the cache is very light-weight.
-    region.setMobFileCache(new MobFileCache(conf));
+    mobFileCache = new MobFileCache(conf);
+    region.setMobFileCache(mobFileCache);
     region.initialize();
 
     // create an internal region scanner
@@ -131,6 +136,19 @@ public void close() {
         LOG.warn("Exception while closing region", ex);
       }
     }
+
+    // In typical region operation, RegionServerServices would handle the lifecycle of
+    // the MobFileCache and BlockCache. In ClientSideRegionScanner, we need to handle
+    // the lifecycle of these components ourselves to avoid resource leaks.
+    if (mobFileCache != null) {
+      mobFileCache.shutdown();
+      mobFileCache = null;
+    }
+
+    if (blockCache != null) {
+      blockCache.shutdown();
+      blockCache = null;
+    }
   }
 
   HRegion getRegion() {