HBASE-28953 Prefetch thread shouldn't run for master store (#6438) (#6445)

Signed-off-by: Peter Somogyi <psomogyi@apache.org>
Signed-off-by: Ankit Singhal <ankit@apache.org>
Signed-off-by: Pankaj Kumar<pankajkumar@apache.org>

Author: wchevreuil

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java

@@ -37,7 +37,8 @@ public class HFilePreadReader extends HFileReaderImpl {
   public HFilePreadReader(ReaderContext context, HFileInfo fileInfo, CacheConfig cacheConf,
     Configuration conf) throws IOException {
     super(context, fileInfo, cacheConf, conf);
-    final MutableBoolean shouldCache = new MutableBoolean(true);
+    // master hosted regions, like the master procedures store wouldn't have a block cache
+    final MutableBoolean shouldCache = new MutableBoolean(cacheConf.getBlockCache().isPresent());
 
     cacheConf.getBlockCache().ifPresent(cache -> {
       Optional<Boolean> result = cache.shouldCacheFile(path.getName());

hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestPrefetch.java

@@ -349,6 +349,28 @@ public void testPrefetchWithDelay() throws Exception {
     prefetchExecutorNotifier.onConfigurationChange(conf);
   }
 
+  @Test
+  public void testPrefetchWhenNoBlockCache() throws Exception {
+    PrefetchExecutorNotifier prefetchExecutorNotifier = new PrefetchExecutorNotifier(conf);
+    try {
+      // Set a delay to max, as we don't need to have the thread running, but rather
+      // assert that it never gets scheduled
+      conf.setInt(PREFETCH_DELAY, Integer.MAX_VALUE);
+      conf.setFloat(PREFETCH_DELAY_VARIATION, 0.0f);
+      prefetchExecutorNotifier.onConfigurationChange(conf);
+
+      HFileContext context = new HFileContextBuilder().withCompression(Compression.Algorithm.GZ)
+        .withBlockSize(DATA_BLOCK_SIZE).build();
+      Path storeFile = writeStoreFile("testPrefetchWhenNoBlockCache", context);
+      HFile.createReader(fs, storeFile, new CacheConfig(conf), true, conf);
+      assertEquals(0, PrefetchExecutor.getPrefetchFutures().size());
+    } finally {
+      conf.setInt(PREFETCH_DELAY, 1000);
+      conf.setFloat(PREFETCH_DELAY_VARIATION, PREFETCH_DELAY_VARIATION_DEFAULT_VALUE);
+      prefetchExecutorNotifier.onConfigurationChange(conf);
+    }
+  }
+
   @Test
   public void testPrefetchDoesntSkipHFileLink() throws Exception {
     testPrefetchWhenHFileLink(c -> {