[GitHub] [incubator-pinot] kishoreg commented on a change in pull request #4778: Decoupling Server instance name from physical host and port

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kishoreg commented on a change in pull request #4778: Decoupling Server instance name from physical host and port
URL: https://github.com/apache/incubator-pinot/pull/4778#discussion_r342273013
 
 

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 File path: pinot-common/src/main/java/org/apache/pinot/common/helix/HelixInstanceConfigCache.java
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 @@ -0,0 +1,104 @@
+/**
+ * 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.pinot.common.helix;
+
+import com.google.common.base.Preconditions;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.apache.helix.HelixConstants;
+import org.apache.helix.HelixDataAccessor;
+import org.apache.helix.HelixManager;
+import org.apache.helix.PropertyKey;
+import org.apache.helix.model.InstanceConfig;
+import org.apache.pinot.common.helix.ClusterChangeHandler;
+import org.apache.pinot.common.utils.CommonConstants;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * Helper class to maintain a cache of all the {@code INSTANCE_CONFIG} managed by
+ * the Pinot Helix cluster. It provides a singleton object to lookup the host
+ * and port information based on the specified instance name.
+ *
+ * This will be helpful in decoupling instance name from the physical host and port
+ * information (https://github.com/apache/incubator-pinot/issues/4525)
+ */
+public class HelixInstanceConfigCache implements ClusterChangeHandler {
+  private static final Logger LOGGER = LoggerFactory.getLogger(HelixInstanceConfigCache.class);
+  private HelixManager _helixManager;
+  private Map<String, InstanceConfig> _instanceNameToConfigMap;
+  private static HelixInstanceConfigCache _instance;
+  private volatile boolean _initialized;
+
+  private HelixInstanceConfigCache() {
+    _initialized = false;
+  }
+
+  public static synchronized HelixInstanceConfigCache getInstance() {
+    if (_instance == null) {
+      _instance = new HelixInstanceConfigCache();
+    }
+    return _instance;
+  }
+
+  public boolean isInitialized() {
+    return _initialized;
+  }
+
+  @Override
+  public void init(HelixManager helixManager) {
+    Preconditions.checkState(_helixManager == null, "HelixInstanceConfigCache is already initialized");
+    _helixManager = helixManager;
+    _instanceNameToConfigMap = new HashMap<>();
+    _initialized = true;
+  }
+
+  @Override
+  public void processClusterChange(HelixConstants.ChangeType changeType) {
 
 Review comment:
   This might not be efficient when the size of the cluster is large. We already do this in an efficient way in routing table handler.

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