[GitHub] [hbase] bharathv commented on a change in pull request #1095: HBASE-23257: Track clusterID in stand by masters (#798)

[GitBox <gi...@apache.org>]

bharathv commented on a change in pull request #1095: HBASE-23257: Track clusterID in stand by masters (#798)
URL: https://github.com/apache/hbase/pull/1095#discussion_r372135621
 
 

 ##########
 File path: hbase-server/src/main/java/org/apache/hadoop/hbase/master/CachedClusterId.java
 ##########
 @@ -0,0 +1,155 @@
+/*
+ * 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.master;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.ClusterId;
+import org.apache.hadoop.hbase.util.FSUtils;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
+import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
+
+/**
+ * Caches the cluster ID of the cluster. For standby masters, this is used to serve the client
+ * RPCs that fetch the cluster ID. ClusterID is only created by an active master if one does not
+ * already exist. Standby masters just read the information from the file system. This class is
+ * thread-safe.
+ *
+ * TODO: Make it a singleton without affecting concurrent junit tests.
+ */
+@InterfaceAudience.Private
+public class CachedClusterId {
+
+  public static final Logger LOG = LoggerFactory.getLogger(CachedClusterId.class);
+  private static final int MAX_FETCH_TIMEOUT_MS = 10000;
+
+  private Path rootDir;
+  private FileSystem fs;
+
+  // When true, indicates that a FileSystem fetch of ClusterID is in progress. This is used to
+  // avoid multiple fetches from FS and let only one thread fetch the information.
+  AtomicBoolean fetchInProgress = new AtomicBoolean(false);
+
+  // When true, it means that the cluster ID has been fetched successfully from fs.
+  private AtomicBoolean isClusterIdSet = new AtomicBoolean(false);
+  // Immutable once set and read multiple times.
+  private ClusterId clusterId;
+
+  // cache stats for testing.
+  private AtomicInteger cacheMisses = new AtomicInteger(0);
 
 Review comment:
   Agree... wish Java had C++ like macros that we could use to inject DEBUG only code :D.
   
   This code also exists in the master, I'll have to cleanup from there. Can I do it as a follow up?

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services