[GitHub] [hbase] virajjasani commented on a diff in pull request #5181: HBASE-27796 Improve MemcachedBlockCache

["virajjasani (via GitHub)" <gi...@apache.org>]

virajjasani commented on code in PR #5181:
URL: https://github.com/apache/hbase/pull/5181#discussion_r1167370213


##########
hbase-external-blockcache/pom.xml:
##########
@@ -51,7 +51,63 @@
     </dependency>
     <dependency>
       <groupId>org.slf4j</groupId>
-      <artifactId>slf4j-api</artifactId>
+      <artifactId>jcl-over-slf4j</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>jul-to-slf4j</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.logging.log4j</groupId>
+      <artifactId>log4j-api</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.logging.log4j</groupId>
+      <artifactId>log4j-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.logging.log4j</groupId>
+      <artifactId>log4j-slf4j-impl</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.logging.log4j</groupId>
+      <artifactId>log4j-1.2-api</artifactId>
+      <scope>test</scope>
+    </dependency>

Review Comment:
   All these `log4j*` dependencies are required for `jmemcached-core`?



##########
hbase-external-blockcache/src/main/java/org/apache/hadoop/hbase/io/hfile/MemcachedBlockCache.java:
##########
@@ -67,10 +78,20 @@ public class MemcachedBlockCache implements BlockCache {
   public static final String MEMCACHED_OPTIMIZE_KEY = "hbase.cache.memcached.spy.optimze";
   public static final long MEMCACHED_DEFAULT_TIMEOUT = 500;
   public static final boolean MEMCACHED_OPTIMIZE_DEFAULT = false;
+  public static final int STAT_THREAD_PERIOD = 60 * 5;
 
   private final MemcachedClient client;
   private final HFileBlockTranscoder tc = new HFileBlockTranscoder();
   private final CacheStats cacheStats = new CacheStats("MemcachedBlockCache");
+  private final AtomicLong cachedCount = new AtomicLong();
+  private final AtomicLong notCachedCount = new AtomicLong();
+  private final AtomicLong cacheErrorCount = new AtomicLong();
+  private final AtomicLong timeoutCount = new AtomicLong();
+
+  /** Statistics thread schedule pool (for heavy debugging, could remove) */
+  private transient final ScheduledExecutorService scheduleThreadPool =
+    Executors.newScheduledThreadPool(1, new ThreadFactoryBuilder()
+      .setNameFormat("MemcachedBlockCacheStatsExecutor").setDaemon(true).build());

Review Comment:
   Since it is meant for debugging, shall we initialize the thread pool with only some configuration (default off)?



##########
hbase-external-blockcache/src/test/java/org/apache/hadoop/hbase/io/hfile/TestMemcachedBlockCache.java:
##########
@@ -0,0 +1,124 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.io.hfile;
+
+import static org.junit.Assert.assertEquals;
+
+import com.thimbleware.jmemcached.CacheElement;
+import com.thimbleware.jmemcached.CacheImpl;
+import com.thimbleware.jmemcached.Key;
+import com.thimbleware.jmemcached.LocalCacheElement;
+import com.thimbleware.jmemcached.MemCacheDaemon;
+import com.thimbleware.jmemcached.storage.hash.ConcurrentLinkedHashMap;
+import com.thimbleware.jmemcached.storage.hash.ConcurrentLinkedHashMap.EvictionPolicy;
+import java.net.InetSocketAddress;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtil;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.Waiter;
+import org.apache.hadoop.hbase.io.hfile.CacheTestUtils.HFileBlockPair;
+import org.apache.hadoop.hbase.testclassification.IOTests;
+import org.apache.hadoop.hbase.testclassification.LargeTests;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category({ IOTests.class, LargeTests.class })
+public class TestMemcachedBlockCache {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestMemcachedBlockCache.class);
+
+  static MemCacheDaemon<? extends CacheElement> MEMCACHED;
+  static MemcachedBlockCache CACHE;
+
+  @Before
+  public void before() throws Exception {
+    MEMCACHED.getCache().flush_all();
+    assertEquals("Memcache is not empty", MEMCACHED.getCache().getCurrentItems(), 0);
+  }
+
+  @BeforeClass
+  public static void setup() throws Exception {
+    int port = HBaseTestingUtil.randomFreePort();
+    MEMCACHED = createDaemon(port);
+    Configuration conf = new Configuration();
+    conf.set("hbase.cache.memcached.servers", "localhost:" + port);
+    CACHE = new MemcachedBlockCache(conf);
+  }
+
+  @AfterClass
+  public static void tearDown() throws Exception {
+    if (MEMCACHED != null) {
+      MEMCACHED.stop();
+    }
+  }
+
+  @Test
+  public void testCache() throws Exception {
+    final int NUM_BLOCKS = 10;
+    HFileBlockPair[] blocks =
+      CacheTestUtils.generateHFileBlocks(HConstants.DEFAULT_BLOCKSIZE, NUM_BLOCKS);
+    for (int i = 0; i < NUM_BLOCKS; i++) {
+      CACHE.cacheBlock(blocks[i].getBlockName(), blocks[i].getBlock());
+    }
+    Waiter.waitFor(new Configuration(), 10000,
+      () -> MEMCACHED.getCache().getCurrentItems() == NUM_BLOCKS);
+  }
+
+  @Test
+  public void testEviction() throws Exception {
+    final int NUM_BLOCKS = 10;
+    HFileBlockPair[] blocks =
+      CacheTestUtils.generateHFileBlocks(HConstants.DEFAULT_BLOCKSIZE, NUM_BLOCKS);
+    for (int i = 0; i < NUM_BLOCKS; i++) {
+      CACHE.cacheBlock(blocks[i].getBlockName(), blocks[i].getBlock());
+    }
+    Waiter.waitFor(new Configuration(), 10000,
+      () -> MEMCACHED.getCache().getCurrentItems() == NUM_BLOCKS);
+    for (int i = 0; i < NUM_BLOCKS; i++) {
+      CACHE.evictBlock(blocks[i].getBlockName());
+    }
+    Waiter.waitFor(new Configuration(), 10000, () -> MEMCACHED.getCache().getCurrentItems() == 0);
+  }
+
+  private static MemCacheDaemon<? extends CacheElement> createDaemon(int port) {

Review Comment:
   Looks like we didn't have tests so far that runs memcached locally?



##########
hbase-external-blockcache/src/main/java/org/apache/hadoop/hbase/io/hfile/MemcachedBlockCache.java:
##########
@@ -139,17 +165,24 @@ public Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repea
     try (Scope traceScope = span.makeCurrent()) {
       result = client.get(cacheKey.toString(), tc);
     } catch (Exception e) {
-      // Catch a pretty broad set of exceptions to limit any changes in the memecache client
+      // Catch a pretty broad set of exceptions to limit any changes in the memcache client
       // and how it handles failures from leaking into the read path.
-      if (LOG.isDebugEnabled()) {
-        LOG.debug(
-          "Exception pulling from memcached [ " + cacheKey.toString() + " ]. Treating as a miss.",
-          e);
+      if (
+        (e instanceof OperationTimeoutException) || ((e instanceof RuntimeException)
+          && (e.getCause() instanceof OperationTimeoutException))
+      ) {
+        timeoutCount.incrementAndGet();
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("Timeout getting key " + cacheKey.toString(), e);
+        }
+      } else {
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("Exception getting key " + cacheKey.toString(), e);
+        }
       }

Review Comment:
   We need to increment `cacheErrorCount` correct?



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