leventov commented on a change in pull request #9172: Fix huge number of watches in zk URL: https://github.com/apache/druid/pull/9172#discussion_r365800681
########## File path: server/src/main/java/org/apache/druid/curator/announcement/NodeAnnouncer.java ########## @@ -0,0 +1,350 @@ +/* + * 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.curator.announcement; + +import com.google.common.annotations.VisibleForTesting; +import org.apache.curator.framework.CuratorFramework; +import org.apache.curator.framework.api.transaction.CuratorOp; +import org.apache.curator.framework.recipes.cache.ChildData; +import org.apache.curator.framework.recipes.cache.NodeCache; +import org.apache.druid.java.util.common.IAE; +import org.apache.druid.java.util.common.ISE; +import org.apache.druid.java.util.common.guava.CloseQuietly; +import org.apache.druid.java.util.common.io.Closer; +import org.apache.druid.java.util.common.lifecycle.LifecycleStart; +import org.apache.druid.java.util.common.lifecycle.LifecycleStop; +import org.apache.druid.java.util.common.logger.Logger; +import org.apache.druid.server.ZKPathsUtils; +import org.apache.zookeeper.CreateMode; +import org.apache.zookeeper.KeeperException; + +import javax.annotation.concurrent.GuardedBy; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.List; +import java.util.Set; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.CopyOnWriteArrayList; + +/** + * NodeAnnouncer announces single node on Zookeeper and only watches this node, + * while {@link Announcer} watches all child paths, not only this node + */ +public class NodeAnnouncer +{ + private static final Logger log = new Logger(NodeAnnouncer.class); + + private final CuratorFramework curator; + + /** + * In case a path is added to this collection in {@link #announce} before zk is connected, + * should remember the path and do announce in {@link #start} later. + */ + private final List<Announceable> toAnnounce = new ArrayList<>(); + /** + * In case a path is added to this collection in {@link #update} before zk is connected, + * should remember the path and do update in {@link #start} later. + */ + @GuardedBy("toAnnounce") + private final List<Announceable> toUpdate = new ArrayList<>(); + private final ConcurrentMap<String, NodeCache> listeners = new ConcurrentHashMap<>(); + private final ConcurrentMap<String, byte[]> announcedPaths = new ConcurrentHashMap<>(); + /** + * Only the one created the parent path can drop the parent path, so should remember these created parents. + */ + private final List<String> pathsCreatedInThisAnnouncer = new CopyOnWriteArrayList<>(); + + private boolean started = false; + + public NodeAnnouncer(CuratorFramework curator) + { + this.curator = curator; + } + + @VisibleForTesting + Set<String> getAddedPaths() + { + return announcedPaths.keySet(); + } + + @LifecycleStart + @SuppressWarnings("DuplicatedCode") + public void start() + { + log.info("Starting announcer"); + synchronized (toAnnounce) { + if (started) { + return; + } + + started = true; + + for (Announceable announceable : toAnnounce) { + announce(announceable.path, announceable.bytes, announceable.removeParentsIfCreated); + } + toAnnounce.clear(); + + for (Announceable announceable : toUpdate) { + update(announceable.path, announceable.bytes); + } + toUpdate.clear(); + } + } + + @LifecycleStop + public void stop() + { + log.info("Stopping announcer"); + synchronized (toAnnounce) { + if (!started) { + return; + } + + started = false; + + Closer closer = Closer.create(); + for (NodeCache cache : listeners.values()) { + closer.register(cache); + } + CloseQuietly.close(closer); + + for (String announcementPath : announcedPaths.keySet()) { + unannounce(announcementPath); + } + + if (!pathsCreatedInThisAnnouncer.isEmpty()) { + final List<CuratorOp> deleteOps = new ArrayList<>(pathsCreatedInThisAnnouncer.size()); + for (String parent : pathsCreatedInThisAnnouncer) { + try { + deleteOps.add(curator.transactionOp().delete().forPath(parent)); + } + catch (Exception e) { + log.error(e, "Unable to delete parent[%s].", parent); + } + } + try { + curator.transaction().forOperations(deleteOps); + } + catch (Exception e) { + log.error(e, "Unable to commit transaction."); + } + } + } + } + + /** + * Like announce(path, bytes, true). + */ + public void announce(String path, byte[] bytes) + { + announce(path, bytes, true); + } + + /** + * Announces the provided bytes at the given path. Announcement means that it will create an ephemeral node + * and monitor it to make sure that it always exists until it is unannounced or this object is closed. + * + * @param path The path to announce at + * @param bytes The payload to announce + * @param removeParentIfCreated remove parent of "path" if we had created that parent + */ + public void announce(String path, byte[] bytes, boolean removeParentIfCreated) + { + synchronized (toAnnounce) { + if (!started) { + toAnnounce.add(new Announceable(path, bytes, removeParentIfCreated)); + return; + } + } + + final String parentPath = ZKPathsUtils.getParentPath(path); + boolean buildParentPath = false; + + byte[] value = announcedPaths.get(path); + + if (value == null) { + try { + if (curator.checkExists().forPath(parentPath) == null) { + buildParentPath = true; + } + } + catch (Exception e) { + log.debug(e, "Problem checking if the parent existed, ignoring."); + } + + // Synchronize to make sure that I only create a listener once. + synchronized (toAnnounce) { + if (!listeners.containsKey(path)) { + final NodeCache cache = new NodeCache(curator, path, true); + cache.getListenable().addListener( + () -> { + ChildData currentData = cache.getCurrentData(); + if (currentData == null) { + final byte[] value1 = announcedPaths.get(path); + if (value1 != null) { + log.info("Node[%s] dropped, reinstating.", path); + createAnnouncement(path, value1); + } + } + } + ); + + if (started) { + if (buildParentPath) { + createPath(parentPath, removeParentIfCreated); + } + startCache(cache); + listeners.put(path, cache); + } + } + } + } + + boolean created = false; + synchronized (toAnnounce) { + if (started) { + byte[] oldBytes = announcedPaths.putIfAbsent(path, bytes); Review comment: Please move the logic into `compute()` so when `IAE` is thrown the state is not changed. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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