[GitHub] gianm commented on a change in pull request #7088: Improve parallelism of zookeeper based segment change processing

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

gianm commented on a change in pull request #7088: Improve parallelism of zookeeper based segment change processing
URL: https://github.com/apache/incubator-druid/pull/7088#discussion_r258306927
 
 

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 File path: server/src/main/java/org/apache/druid/server/coordinator/CuratorLoadQueuePeonV2.java
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+/*
+ * 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.druid.server.coordinator;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.collect.ImmutableList;
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import org.apache.curator.framework.CuratorFramework;
+import org.apache.curator.framework.api.CuratorWatcher;
+import org.apache.curator.utils.ZKPaths;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.java.util.emitter.EmittingLogger;
+import org.apache.druid.server.coordination.DataSegmentChangeRequest;
+import org.apache.druid.server.coordination.SegmentChangeRequestDrop;
+import org.apache.druid.server.coordination.SegmentChangeRequestLoad;
+import org.apache.druid.server.coordination.SegmentChangeRequestNoop;
+import org.apache.druid.timeline.DataSegment;
+import org.apache.druid.timeline.SegmentId;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.data.Stat;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ConcurrentSkipListMap;
+import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Use {@link HttpLoadQueuePeon} instead.
+ */
+@Deprecated
+public class CuratorLoadQueuePeonV2 extends LoadQueuePeon
+{
+  private static final EmittingLogger log = new EmittingLogger(CuratorLoadQueuePeon.class);
+  private static final int DROP = 0;
+  private static final int LOAD = 1;
+  private final CuratorFramework curator;
+  private final String basePath;
+  private final ObjectMapper jsonMapper;
+  private final ExecutorService processingExecutor;
+  private final ScheduledExecutorService checkNodeRemovedExecutor;
+  private final ExecutorService callBackExecutor;
+  private final DruidCoordinatorConfig config;
+
+  private final AtomicLong queuedSize = new AtomicLong(0);
+  private final AtomicInteger failedAssignCount = new AtomicInteger(0);
+
+  private final ConcurrentSkipListMap<DataSegment, SegmentHolder> segmentsToLoad = new ConcurrentSkipListMap<>(
+      DruidCoordinator.SEGMENT_COMPARATOR
+  );
+  private final ConcurrentSkipListMap<DataSegment, SegmentHolder> segmentsToDrop = new ConcurrentSkipListMap<>(
+      DruidCoordinator.SEGMENT_COMPARATOR
+  );
+  private final ConcurrentSkipListSet<DataSegment> segmentsMarkedToDrop = new ConcurrentSkipListSet<>(
+      DruidCoordinator.SEGMENT_COMPARATOR
+  );
+
+  private static final int MAX_TASK_WAIT = 100;
+
+  CuratorLoadQueuePeonV2(
+      CuratorFramework curator,
+      String basePath,
+      ObjectMapper jsonMapper,
+      ExecutorService processingExecutor,
+      ExecutorService callbackExecutor,
+      DruidCoordinatorConfig config
+  )
+  {
+    this.curator = curator;
+    this.basePath = basePath;
+    this.jsonMapper = jsonMapper;
+    this.callBackExecutor = callbackExecutor;
+    this.processingExecutor = processingExecutor;
+    this.config = config;
+    //TODO: samarth configure the size of this pool
+    this.checkNodeRemovedExecutor = Executors.newScheduledThreadPool(5, new ThreadFactoryBuilder().setNameFormat(
+        "ZKNodeDeletionChecker--%d").build());
+  }
+
+  @JsonProperty
+  @Override
+  public Set<DataSegment> getSegmentsToLoad()
+  {
+    return segmentsToLoad.keySet();
+  }
+
+  @JsonProperty
+  @Override
+  public Set<DataSegment> getSegmentsToDrop()
+  {
+    return segmentsToDrop.keySet();
+  }
+
+  @JsonProperty
+  @Override
+  public Set<DataSegment> getSegmentsMarkedToDrop()
+  {
+    return segmentsMarkedToDrop;
+  }
+
+  @Override
+  public long getLoadQueueSize()
+  {
+    return queuedSize.get();
+  }
+
+  @Override
+  public int getAndResetFailedAssignCount()
+  {
+    return failedAssignCount.getAndSet(0);
+  }
+
+  @Override
+  public int getNumberOfSegmentsInQueue()
+  {
+    return segmentsToLoad.size();
+  }
+
+  @Override
+  public void loadSegment(
+      final DataSegment segment,
+      final LoadPeonCallback callback
+  )
+  {
+
+    final SegmentHolder existingHolder = segmentsToLoad.get(segment);
+    if (existingHolder != null) {
+      if ((callback != null)) {
+        existingHolder.addCallback(callback);
+      }
+      return;
+    }
+    log.info("Asking server peon[%s] to load segment[%s]", basePath, segment.getId());
+    queuedSize.addAndGet(segment.getSize());
+    SegmentHolder holder = new SegmentHolder(segment, LOAD, Collections.singletonList(callback));
+    segmentsToLoad.put(segment, holder);
+    processingExecutor.submit((Callable<Void>) () -> {
+      processSegmentChangeRequest(holder);
+      return null;
+    });
+  }
+
+  @Override
+  public void dropSegment(
+      final DataSegment segment,
+      final LoadPeonCallback callback
+  )
+  {
+    final SegmentHolder existingHolder = segmentsToDrop.get(segment);
+    if (existingHolder != null) {
+      if (callback != null) {
+        existingHolder.addCallback(callback);
+      }
+      return;
+    }
+    log.info("Asking server peon[%s] to drop segment[%s]", basePath, segment.getId());
+    SegmentHolder segmentHolder = new SegmentHolder(segment, DROP, Collections.singletonList(callback));
+    segmentsToDrop.put(segment, segmentHolder);
+    processingExecutor.submit((Callable<Void>) () -> {
+      processSegmentChangeRequest(segmentHolder);
+      return null;
+    });
+  }
+
+  @Override
+  public void markSegmentToDrop(DataSegment dataSegment)
+  {
+    segmentsMarkedToDrop.add(dataSegment);
+  }
+
+  @Override
+  public void unmarkSegmentToDrop(DataSegment dataSegment)
+  {
+    segmentsMarkedToDrop.remove(dataSegment);
+  }
+
+  private void processSegmentChangeRequest(SegmentHolder segmentHolder)
+  {
+    try {
+      // Wait for a random duration since we do not want zookeeper getting pounded with create node requests
+      TimeUnit.MILLISECONDS.sleep(ThreadLocalRandom.current().nextInt(MAX_TASK_WAIT));
+      log.info("Server[%s] %s [%s]", basePath, segmentHolder.getType() == LOAD ?
+                                               "loading" : "dropping", segmentHolder.getSegmentId().toString());
+      final String path = ZKPaths.makePath(basePath, segmentHolder.getSegmentId().toString());
+      final byte[] payload = jsonMapper.writeValueAsBytes(segmentHolder.getChangeRequest());
+      curator.create().withMode(CreateMode.EPHEMERAL).forPath(path, payload);
+
+      checkNodeRemovedExecutor.schedule(
+          () -> {
+            try {
+              if (curator.checkExists().forPath(path) != null) {
+                failAssign(segmentHolder, new ISE("%s was never removed! Failing this operation!", path));
+              } else {
+                log.info("%s detected to be removed. ", path);
 
 Review comment:
   This could stand to be at `log.debug`, I think. (In the spirit of #6741 & trying to keep log chatter on the coordinator useful by not being too noisy.)

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