HBASE-22610 [BucketCache] Rename hbase.offheapcache.minblocksize

* HBASE-22610 [BucketCache] Rename hbase.offheapcache.minblocksize.

* HBASE-22610 [BucketCache] Rename hbase.offheapcache.minblocksize. Deprecated old attribute and introduced a new one

* HBASE-22610 [BucketCache] Rename hbase.offheapcache.minblocksize. Removed unnecessary import

* HBASE-22610 added two import configs and removed one

Signed-off-by: Reid Chan <reidchan@apache.org>

Author: murtazahassan123

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

@@ -78,20 +78,38 @@ public final class BlockCacheFactory {
   /**
    * The target block size used by blockcache instances. Defaults to
    * {@link HConstants#DEFAULT_BLOCKSIZE}.
-   * TODO: this config point is completely wrong, as it's used to determine the
-   * target block size of BlockCache instances. Rename.
    */
-  public static final String BLOCKCACHE_BLOCKSIZE_KEY = "hbase.offheapcache.minblocksize";
+  public static final String BLOCKCACHE_BLOCKSIZE_KEY = "hbase.blockcache.minblocksize";
 
   private static final String EXTERNAL_BLOCKCACHE_KEY = "hbase.blockcache.use.external";
   private static final boolean EXTERNAL_BLOCKCACHE_DEFAULT = false;
 
   private static final String EXTERNAL_BLOCKCACHE_CLASS_KEY = "hbase.blockcache.external.class";
 
+  /**
+   * @deprecated use {@link BlockCacheFactory#BLOCKCACHE_BLOCKSIZE_KEY} instead.
+   */
+  @Deprecated
+  static final String DEPRECATED_BLOCKCACHE_BLOCKSIZE_KEY = "hbase.blockcache.minblocksize";
+
+  /**
+   * The config point hbase.offheapcache.minblocksize is completely wrong, which is replaced by
+   * {@link BlockCacheFactory#BLOCKCACHE_BLOCKSIZE_KEY}. Keep the old config key here for backward
+   * compatibility.
+   */
+  static {
+    Configuration.addDeprecation(DEPRECATED_BLOCKCACHE_BLOCKSIZE_KEY, BLOCKCACHE_BLOCKSIZE_KEY);
+  }
+
   private BlockCacheFactory() {
   }
 
   public static BlockCache createBlockCache(Configuration conf) {
+    if (conf.get(DEPRECATED_BLOCKCACHE_BLOCKSIZE_KEY) != null) {
+      LOG.warn("The config key {} is deprecated now, instead please use {}. In future release "
+            + "we will remove the deprecated config.", DEPRECATED_BLOCKCACHE_BLOCKSIZE_KEY,
+        BLOCKCACHE_BLOCKSIZE_KEY);
+    }
     FirstLevelBlockCache l1Cache = createFirstLevelCache(conf);
     if (l1Cache == null) {
       return null;