HBASE-28953 Prefetch thread shouldn't run for master store

Author: wchevreuil

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

@@ -39,24 +39,24 @@ public class HFilePreadReader extends HFileReaderImpl {
   public HFilePreadReader(ReaderContext context, HFileInfo fileInfo, CacheConfig cacheConf,
     Configuration conf) throws IOException {
     super(context, fileInfo, cacheConf, conf);
-
+    // master hosted regions, like the master procedures store wouldn't have a block cache
+    final MutableBoolean shouldCache = new MutableBoolean(cacheConf.getBlockCache().isPresent());
     // Prefetch file blocks upon open if requested
-    if (cacheConf.shouldPrefetchOnOpen()) {
+    if (shouldCache.booleanValue() && cacheConf.shouldPrefetchOnOpen()) {
       PrefetchExecutor.request(path, new Runnable() {
         @Override
         public void run() {
           long offset = 0;
           long end = 0;
           HFile.Reader prefetchStreamReader = null;
-          final MutableBoolean shouldCache = new MutableBoolean(true);
           try {
             cacheConf.getBlockCache().ifPresent(cache -> {
               cache.waitForCacheInitialization(WAIT_TIME_FOR_CACHE_INITIALIZATION);
               Optional<Boolean> result = cache.shouldCacheFile(path.getName());
               shouldCache.setValue(result.isPresent() ? result.get().booleanValue() : true);
             });
             if (!shouldCache.booleanValue()) {
-              LOG.info("Prefetch skipped for the file: " + path.getName());
+              LOG.info("Prefetch skipped for file: {}", path);
               return;
             }
 

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

@@ -378,6 +378,28 @@ 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 -> {