HBASE-16993 BucketCache throw java.io.IOException: Invalid HFile block magic when configuring hbase.bucketcache.bucket.sizes.

hbase-common/src/main/resources/hbase-default.xml

@@ -905,7 +905,7 @@ possible configurations would overwhelm and obscure the important.
     <description>A comma-separated list of sizes for buckets for the bucketcache.
     Can be multiple sizes. List block sizes in order from smallest to largest.
     The sizes you use will depend on your data access patterns.
-    Must be a multiple of 1024 else you will run into
+    Must be a multiple of 256 else you will run into
     'java.io.IOException: Invalid HFile block magic' when you go to read from cache.
     If you specify no values here, then you pick up the default bucketsizes set
     in code (See BucketAllocator#DEFAULT_BUCKET_SIZES).

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

@@ -584,7 +584,8 @@ public class CacheConfig {
    * @return Returns L2 block cache instance (for now it is BucketCache BlockCache all the time)
    * or null if not supposed to be a L2.
    */
-  private static BlockCache getL2(final Configuration c) {
+  @VisibleForTesting
+  static BlockCache getL2(final Configuration c) {
     final boolean useExternal = c.getBoolean(EXTERNAL_BLOCKCACHE_KEY, EXTERNAL_BLOCKCACHE_DEFAULT);
     if (LOG.isDebugEnabled()) {
       LOG.debug("Trying to use " + (useExternal?" External":" Internal") + " l2 cache");
@@ -594,10 +595,8 @@ public class CacheConfig {
     if (useExternal) {
       return getExternalBlockcache(c);
     }
-
     // otherwise use the bucket cache.
     return getBucketCache(c);
-
   }
 
   private static BlockCache getExternalBlockcache(Configuration c) {
@@ -651,7 +650,17 @@ public class CacheConfig {
     if (configuredBucketSizes != null) {
       bucketSizes = new int[configuredBucketSizes.length];
       for (int i = 0; i < configuredBucketSizes.length; i++) {
-        bucketSizes[i] = Integer.parseInt(configuredBucketSizes[i].trim());
+        int bucketSize = Integer.parseInt(configuredBucketSizes[i].trim());
+        if (bucketSize % 256 != 0) {
+          // We need all the bucket sizes to be multiples of 256. Having all the configured bucket
+          // sizes to be multiples of 256 will ensure that the block offsets within buckets,
+          // that are calculated, will also be multiples of 256.
+          // See BucketEntry where offset to each block is represented using 5 bytes (instead of 8
+          // bytes long). We would like to save heap overhead as less as possible.
+          throw new IllegalArgumentException("Illegal value: " + bucketSize + " configured for '"
+              + BUCKET_CACHE_BUCKETS_KEY + "'. All bucket sizes to be multiples of 256");
+        }
+        bucketSizes[i] = bucketSize;
       }
     }
     BucketCache bucketCache = null;

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

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.io.hfile;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import java.io.IOException;
 import java.lang.management.ManagementFactory;
@@ -414,6 +415,19 @@ public class TestCacheConfig {
     assertDataBlockCount(lrubc, 1);
   }
 
+  @Test
+  public void testL2CacheWithInvalidBucketSize() {
+    Configuration c = new Configuration(this.conf);
+    c.set(HConstants.BUCKET_CACHE_IOENGINE_KEY, "offheap");
+    c.set(CacheConfig.BUCKET_CACHE_BUCKETS_KEY, "256,512,1024,2048,4000,4096");
+    c.setFloat(HConstants.BUCKET_CACHE_SIZE_KEY, 1024);
+    try {
+      CacheConfig.getL2(c);
+      fail("Should throw IllegalArgumentException when passing illegal value for bucket size");
+    } catch (IllegalArgumentException e) {
+    }
+  }
+
   private void assertDataBlockCount(final LruBlockCache bc, final int expected) {
     Map<BlockType, Integer> blocks = bc.getBlockTypeCountsForTest();
     assertEquals(expected, blocks == null? 0: