io.druid.curator.announcement.Announcer Maven / Gradle / Ivy
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/*
* Druid - a distributed column store.
* Copyright (C) 2012, 2013 Metamarkets Group Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package io.druid.curator.announcement;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.collect.MapMaker;
import com.google.common.collect.Sets;
import com.google.common.io.Closeables;
import com.metamx.common.IAE;
import com.metamx.common.ISE;
import com.metamx.common.Pair;
import com.metamx.common.lifecycle.LifecycleStart;
import com.metamx.common.lifecycle.LifecycleStop;
import com.metamx.common.logger.Logger;
import io.druid.curator.ShutdownNowIgnoringExecutorService;
import io.druid.curator.cache.PathChildrenCacheFactory;
import io.druid.curator.cache.SimplePathChildrenCacheFactory;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.utils.ZKPaths;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.data.Stat;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicReference;
/**
* Announces things on Zookeeper.
*/
public class Announcer
{
private static final Logger log = new Logger(Announcer.class);
private final CuratorFramework curator;
private final PathChildrenCacheFactory factory;
private final List> toAnnounce = Lists.newArrayList();
private final List> toUpdate = Lists.newArrayList();
private final ConcurrentMap listeners = new MapMaker().makeMap();
private final ConcurrentMap> announcements = new MapMaker().makeMap();
private final List parentsIBuilt = new CopyOnWriteArrayList();
private boolean started = false;
public Announcer(
CuratorFramework curator,
ExecutorService exec
)
{
this.curator = curator;
this.factory = new SimplePathChildrenCacheFactory(false, true, new ShutdownNowIgnoringExecutorService(exec));
}
@LifecycleStart
public void start()
{
synchronized (toAnnounce) {
if (started) {
return;
}
started = true;
for (Pair pair : toAnnounce) {
announce(pair.lhs, pair.rhs);
}
toAnnounce.clear();
for (Pair pair : toUpdate) {
update(pair.lhs, pair.rhs);
}
toUpdate.clear();
}
}
@LifecycleStop
public void stop()
{
synchronized (toAnnounce) {
if (!started) {
return;
}
started = false;
for (Map.Entry entry : listeners.entrySet()) {
Closeables.closeQuietly(entry.getValue());
}
for (Map.Entry> entry : announcements.entrySet()) {
String basePath = entry.getKey();
for (String announcementPath : entry.getValue().keySet()) {
unannounce(ZKPaths.makePath(basePath, announcementPath));
}
}
for (String parent : parentsIBuilt) {
try {
curator.delete().forPath(parent);
}
catch (Exception e) {
log.info(e, "Unable to delete parent[%s], boooo.", parent);
}
}
}
}
/**
* 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
*/
public void announce(String path, byte[] bytes)
{
synchronized (toAnnounce) {
if (!started) {
toAnnounce.add(Pair.of(path, bytes));
return;
}
}
final ZKPaths.PathAndNode pathAndNode = ZKPaths.getPathAndNode(path);
final String parentPath = pathAndNode.getPath();
boolean buildParentPath = false;
ConcurrentMap subPaths = announcements.get(parentPath);
if (subPaths == null) {
try {
if (curator.checkExists().forPath(parentPath) == null) {
buildParentPath = true;
}
}
catch (Exception e) {
log.debug(e, "Problem checking if the parent existed, ignoring.");
}
// I don't have a watcher on this path yet, create a Map and start watching.
announcements.putIfAbsent(parentPath, new MapMaker().makeMap());
// Guaranteed to be non-null, but might be a map put in there by another thread.
final ConcurrentMap finalSubPaths = announcements.get(parentPath);
// Synchronize to make sure that I only create a listener once.
synchronized (finalSubPaths) {
if (!listeners.containsKey(parentPath)) {
final PathChildrenCache cache = factory.make(curator, parentPath);
cache.getListenable().addListener(
new PathChildrenCacheListener()
{
private final AtomicReference> pathsLost = new AtomicReference>(null);
@Override
public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception
{
log.debug("Path[%s] got event[%s]", parentPath, event);
switch (event.getType()) {
case CHILD_REMOVED:
final ChildData child = event.getData();
final ZKPaths.PathAndNode childPath = ZKPaths.getPathAndNode(child.getPath());
final byte[] value = finalSubPaths.get(childPath.getNode());
if (value != null) {
log.info("Node[%s] dropped, reinstating.", child.getPath());
createAnnouncement(child.getPath(), value);
}
break;
case CONNECTION_LOST:
// Lost connection, which means session is broken, take inventory of what has been seen.
// This is to protect from a race condition in which the ephemeral node could have been
// created but not actually seen by the PathChildrenCache, which means that it won't know
// that it disappeared and thus will not generate a CHILD_REMOVED event for us. Under normal
// circumstances, this can only happen upon connection loss; but technically if you have
// an adversary in the system, they could also delete the ephemeral node before the cache sees
// it. This does not protect from that case, so don't have adversaries.
Set pathsToReinstate = Sets.newHashSet();
for (String node : finalSubPaths.keySet()) {
String path = ZKPaths.makePath(parentPath, node);
log.info("Node[%s] is added to reinstate.", path);
pathsToReinstate.add(path);
}
if (!pathsToReinstate.isEmpty() && !pathsLost.compareAndSet(null, pathsToReinstate)) {
log.info("Already had a pathsLost set!?[%s]", parentPath);
}
break;
case CONNECTION_RECONNECTED:
final Set thePathsLost = pathsLost.getAndSet(null);
if (thePathsLost != null) {
for (String path : thePathsLost) {
log.info("Reinstating [%s]", path);
final ZKPaths.PathAndNode split = ZKPaths.getPathAndNode(path);
createAnnouncement(path, announcements.get(split.getPath()).get(split.getNode()));
}
}
break;
}
}
}
);
synchronized (toAnnounce) {
if (started) {
if (buildParentPath) {
createPath(parentPath);
}
startCache(cache);
listeners.put(parentPath, cache);
}
}
}
}
subPaths = finalSubPaths;
}
boolean created = false;
synchronized (toAnnounce) {
if (started) {
byte[] oldBytes = subPaths.putIfAbsent(pathAndNode.getNode(), bytes);
if (oldBytes == null) {
created = true;
} else if (!Arrays.equals(oldBytes, bytes)) {
throw new IAE("Cannot reannounce different values under the same path");
}
}
}
if (created) {
try {
createAnnouncement(path, bytes);
}
catch (Exception e) {
throw Throwables.propagate(e);
}
}
}
public void update(final String path, final byte[] bytes)
{
synchronized (toAnnounce) {
if (!started) {
toUpdate.add(Pair.of(path, bytes));
return;
}
}
final ZKPaths.PathAndNode pathAndNode = ZKPaths.getPathAndNode(path);
final String parentPath = pathAndNode.getPath();
final String nodePath = pathAndNode.getNode();
ConcurrentMap subPaths = announcements.get(parentPath);
if (subPaths == null || subPaths.get(nodePath) == null) {
throw new ISE("Cannot update a path[%s] that hasn't been announced!", path);
}
synchronized (toAnnounce) {
try {
byte[] oldBytes = subPaths.get(nodePath);
if (!Arrays.equals(oldBytes, bytes)) {
subPaths.put(nodePath, bytes);
updateAnnouncement(path, bytes);
}
}
catch (Exception e) {
throw Throwables.propagate(e);
}
}
}
private String createAnnouncement(final String path, byte[] value) throws Exception
{
return curator.create().compressed().withMode(CreateMode.EPHEMERAL).inBackground().forPath(path, value);
}
private Stat updateAnnouncement(final String path, final byte[] value) throws Exception
{
return curator.setData().compressed().inBackground().forPath(path, value);
}
/**
* Unannounces an announcement created at path. Note that if all announcements get removed, the Announcer
* will continue to have ZK watches on paths because clearing them out is a source of ugly race conditions.
*
* If you need to completely clear all the state of what is being watched and announced, stop() the Announcer.
*
* @param path
*/
public void unannounce(String path)
{
log.info("unannouncing [%s]", path);
final ZKPaths.PathAndNode pathAndNode = ZKPaths.getPathAndNode(path);
final String parentPath = pathAndNode.getPath();
final ConcurrentMap subPaths = announcements.get(parentPath);
if (subPaths == null || subPaths.remove(pathAndNode.getNode()) == null) {
log.error("Path[%s] not announced, cannot unannounce.", path);
return;
}
try {
curator.delete().guaranteed().forPath(path);
}
catch (KeeperException.NoNodeException e) {
log.info("node[%s] didn't exist anyway...", path);
}
catch (Exception e) {
throw Throwables.propagate(e);
}
}
private void startCache(PathChildrenCache cache)
{
try {
cache.start();
}
catch (Exception e) {
Closeables.closeQuietly(cache);
throw Throwables.propagate(e);
}
}
private void createPath(String parentPath)
{
try {
curator.create().creatingParentsIfNeeded().forPath(parentPath);
parentsIBuilt.add(parentPath);
}
catch (Exception e) {
log.info(e, "Problem creating parentPath[%s], someone else created it first?", parentPath);
}
}
}
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