[GitHub] Jackie-Jiang commented on a change in pull request #3885: Actively check cluster changes if there is no callback for a long time

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

Jackie-Jiang commented on a change in pull request #3885: Actively check cluster changes if there is no callback for a long time
URL: https://github.com/apache/incubator-pinot/pull/3885#discussion_r260568919
 
 

 ##########
 File path: pinot-broker/src/main/java/org/apache/pinot/broker/broker/helix/ClusterChangeMediator.java
 ##########
 @@ -18,142 +18,136 @@
  */
 package org.apache.pinot.broker.broker.helix;
 
-import java.util.ArrayList;
+import com.google.common.base.Preconditions;
 import java.util.List;
-import java.util.concurrent.LinkedBlockingQueue;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
-import org.apache.commons.lang3.tuple.ImmutablePair;
-import org.apache.commons.lang3.tuple.Pair;
+import org.apache.helix.HelixConstants.ChangeType;
 import org.apache.helix.NotificationContext;
+import org.apache.helix.api.listeners.BatchMode;
 import org.apache.helix.api.listeners.ExternalViewChangeListener;
 import org.apache.helix.api.listeners.InstanceConfigChangeListener;
 import org.apache.helix.api.listeners.LiveInstanceChangeListener;
+import org.apache.helix.api.listeners.PreFetch;
 import org.apache.helix.model.ExternalView;
 import org.apache.helix.model.InstanceConfig;
 import org.apache.helix.model.LiveInstance;
-import org.apache.pinot.broker.queryquota.TableQueryQuotaManager;
-import org.apache.pinot.broker.routing.HelixExternalViewBasedRouting;
+import org.apache.pinot.common.metrics.BrokerMeter;
 import org.apache.pinot.common.metrics.BrokerMetrics;
 import org.apache.pinot.common.metrics.BrokerTimer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 
 /**
- * Manages the interactions between Helix cluster changes, the routing table and the connection pool.
+ * The {@code ClusterChangeMediator} handles the changes from Helix cluster.
+ * <p>
+ * <p>If there is no change callback in 1 hour, proactively check changes so that the changes are getting processed even
+ * when callbacks stop working.
+ * <p>NOTE: disable Helix batch-mode and perform deduplication in this class.
+ * <p>NOTE: disable Helix pre-fetch to reduce the ZK accesses.
  */
-public class ClusterChangeMediator implements LiveInstanceChangeListener, ExternalViewChangeListener, InstanceConfigChangeListener {
+@BatchMode(enabled = false)
+@PreFetch(enabled = false)
+public class ClusterChangeMediator implements ExternalViewChangeListener, InstanceConfigChangeListener, LiveInstanceChangeListener {
   private static final Logger LOGGER = LoggerFactory.getLogger(ClusterChangeMediator.class);
-  private final HelixExternalViewBasedRouting _helixExternalViewBasedRouting;
-  private final TableQueryQuotaManager _tableQueryQuotaManager;
 
-  private enum UpdateType {
-    EXTERNAL_VIEW, INSTANCE_CONFIG
-  }
+  private static final long PROACTIVE_CHANGE_CHECK_INTERVAL_MS = 3600 * 1000L;
+
+  private final Map<ChangeType, ClusterChangeHandler> _changeHandlerMap;
+  private final Map<ChangeType, Long> _lastChangeTimeMap = new ConcurrentHashMap<>();
+  private final Map<ChangeType, Long> _lastProcessTimeMap = new ConcurrentHashMap<>();
 
-  private final LinkedBlockingQueue<Pair<UpdateType, Long>> _clusterChangeQueue = new LinkedBlockingQueue<>(1000);
+  private final Thread _clusterChangeHandlingThread;
 
-  private Thread _deferredClusterUpdater = null;
+  public ClusterChangeMediator(Map<ChangeType, ClusterChangeHandler> changeHandlerMap, BrokerMetrics brokerMetrics) {
+    _changeHandlerMap = changeHandlerMap;
 
-  public ClusterChangeMediator(HelixExternalViewBasedRouting helixExternalViewBasedRouting,
-      TableQueryQuotaManager tableQueryQuotaManager, final BrokerMetrics brokerMetrics) {
-    _helixExternalViewBasedRouting = helixExternalViewBasedRouting;
-    _tableQueryQuotaManager = tableQueryQuotaManager;
+    // Initialize last process time map
+    long initTime = System.currentTimeMillis();
+    for (ChangeType changeType : changeHandlerMap.keySet()) {
+      _lastProcessTimeMap.put(changeType, initTime);
+    }
 
-    // Simple thread that polls every 10 seconds to check if there are any cluster updates to apply
-    _deferredClusterUpdater = new Thread("Deferred cluster state updater") {
+    _clusterChangeHandlingThread = new Thread("ClusterChangeHandlingThread") {
       @Override
       public void run() {
         while (true) {
           try {
-            // Wait for at least one update
-            Pair<UpdateType, Long> firstUpdate = _clusterChangeQueue.take();
-
-            // Update the queue time metrics
-            long queueTime = System.currentTimeMillis() - firstUpdate.getValue();
-            brokerMetrics.addTimedValue(BrokerTimer.ROUTING_TABLE_UPDATE_QUEUE_TIME, queueTime, TimeUnit.MILLISECONDS);
-
-            // Take all other updates also present
-            List<Pair<UpdateType, Long>> allUpdates = new ArrayList<>();
-            allUpdates.add(firstUpdate);
-            _clusterChangeQueue.drainTo(allUpdates);
-
-            // Gather all update types
-            boolean externalViewUpdated = false;
-            boolean instanceConfigUpdated = false;
-
-            for (Pair<UpdateType, Long> update : allUpdates) {
-              if (update.getKey() == UpdateType.EXTERNAL_VIEW) {
-                externalViewUpdated = true;
-              } else if (update.getKey() == UpdateType.INSTANCE_CONFIG) {
-                instanceConfigUpdated = true;
-              }
-            }
-
-            if (externalViewUpdated) {
-              try {
-                _helixExternalViewBasedRouting.processExternalViewChange();
-                _tableQueryQuotaManager.processQueryQuotaChange();
-              } catch (Exception e) {
-                LOGGER.warn("Caught exception while updating external view", e);
+            for (Map.Entry<ChangeType, ClusterChangeHandler> entry : _changeHandlerMap.entrySet()) {
+              ChangeType changeType = entry.getKey();
+              ClusterChangeHandler changeHandler = entry.getValue();
+              long currentTime = System.currentTimeMillis();
+              Long lastChangeTime = _lastChangeTimeMap.remove(changeType);
+              if (lastChangeTime != null) {
+                brokerMetrics.addTimedValue(BrokerTimer.CLUSTER_CHANGE_QUEUE_TIME, currentTime - lastChangeTime,
+                    TimeUnit.MILLISECONDS);
+                processClusterChange(changeType, changeHandler);
+              } else {
+                long lastProcessTime = _lastProcessTimeMap.get(changeType);
+                if (currentTime - lastProcessTime > PROACTIVE_CHANGE_CHECK_INTERVAL_MS) {
 
 Review comment:
   This only acts as a fall back mechanism. We should get an INIT callback when we start the cluster.

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