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Posted to commits@hbase.apache.org by bh...@apache.org on 2020/06/25 23:50:07 UTC
[hbase] branch branch-2.3 updated: HBASE-24603: Make Zookeeper
sync() call synchronous (#1945) (#1975)
This is an automated email from the ASF dual-hosted git repository.
bharathv pushed a commit to branch branch-2.3
in repository https://gitbox.apache.org/repos/asf/hbase.git
The following commit(s) were added to refs/heads/branch-2.3 by this push:
new 32f3ed7 HBASE-24603: Make Zookeeper sync() call synchronous (#1945) (#1975)
32f3ed7 is described below
commit 32f3ed780f2656003d077795abe324b3bd91c1be
Author: Bharath Vissapragada <bh...@apache.org>
AuthorDate: Thu Jun 25 16:41:11 2020 -0700
HBASE-24603: Make Zookeeper sync() call synchronous (#1945) (#1975)
Writing a test for this is tricky. There is enough coverage for
functional tests. Only concern is performance, but there is enough
logging for it to detect timed out/badly performing sync calls.
Additionally, this patch decouples the ZK event processing into it's
own thread rather than doing it in the EventThread's context. That
avoids deadlocks and stalls of the event thread.
Signed-off-by: Andrew Purtell <ap...@apache.org>
Signed-off-by: Viraj Jasani <vj...@apache.org>
(cherry picked from commit 84e246f9b197bfa4307172db5465214771b78d38)
---
.../java/org/apache/hadoop/hbase/HConstants.java | 9 +++
.../java/org/apache/hadoop/hbase/util/Threads.java | 2 +-
.../hbase/backup/example/HFileArchiveManager.java | 4 +-
.../visibility/ZKVisibilityLabelWatcher.java | 2 +-
.../hbase/zookeeper/RecoverableZooKeeper.java | 2 +-
.../apache/hadoop/hbase/zookeeper/ZKWatcher.java | 84 +++++++++++++++++-----
6 files changed, 79 insertions(+), 24 deletions(-)
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/HConstants.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/HConstants.java
index e977747..6194e32 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/HConstants.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/HConstants.java
@@ -286,6 +286,15 @@ public final class HConstants {
/** Configuration key for ZooKeeper session timeout */
public static final String ZK_SESSION_TIMEOUT = "zookeeper.session.timeout";
+ /** Timeout for the ZK sync() call */
+ public static final String ZK_SYNC_BLOCKING_TIMEOUT_MS = "hbase.zookeeper.sync.timeout.millis";
+ // Choice of the default value is based on the following ZK recommendation (from docs). Keeping it
+ // lower lets the callers fail fast in case of any issues.
+ // "The clients view of the system is guaranteed to be up-to-date within a certain time bound.
+ // (On the order of tens of seconds.) Either system changes will be seen by a client within this
+ // bound, or the client will detect a service outage."
+ public static final long ZK_SYNC_BLOCKING_TIMEOUT_DEFAULT_MS = 30 * 1000;
+
/** Default value for ZooKeeper session timeout */
public static final int DEFAULT_ZK_SESSION_TIMEOUT = 90 * 1000;
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/util/Threads.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/Threads.java
index 1ca6c2e..3527340 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/util/Threads.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/Threads.java
@@ -204,7 +204,7 @@ public class Threads {
* @param prefix The prefix of every created Thread's name
* @return a {@link java.util.concurrent.ThreadFactory} that names threads
*/
- private static ThreadFactory getNamedThreadFactory(final String prefix) {
+ public static ThreadFactory getNamedThreadFactory(final String prefix) {
SecurityManager s = System.getSecurityManager();
final ThreadGroup threadGroup = (s != null) ? s.getThreadGroup() : Thread.currentThread()
.getThreadGroup();
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/backup/example/HFileArchiveManager.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/backup/example/HFileArchiveManager.java
index f93c3c0..9978f4a 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/backup/example/HFileArchiveManager.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/backup/example/HFileArchiveManager.java
@@ -124,7 +124,7 @@ class HFileArchiveManager {
*/
private void disable(ZKWatcher zooKeeper, byte[] table) throws KeeperException {
// ensure the latest state of the archive node is found
- zooKeeper.sync(archiveZnode);
+ zooKeeper.syncOrTimeout(archiveZnode);
// if the top-level archive node is gone, then we are done
if (ZKUtil.checkExists(zooKeeper, archiveZnode) < 0) {
@@ -133,7 +133,7 @@ class HFileArchiveManager {
// delete the table node, from the archive
String tableNode = this.getTableNode(table);
// make sure the table is the latest version so the delete takes
- zooKeeper.sync(tableNode);
+ zooKeeper.syncOrTimeout(tableNode);
LOG.debug("Attempting to delete table node:" + tableNode);
ZKUtil.deleteNodeRecursively(zooKeeper, tableNode);
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/ZKVisibilityLabelWatcher.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/ZKVisibilityLabelWatcher.java
index 0bbc8d3..bcb3b8b 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/ZKVisibilityLabelWatcher.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/ZKVisibilityLabelWatcher.java
@@ -111,7 +111,7 @@ public class ZKVisibilityLabelWatcher extends ZKListener {
public void nodeDataChanged(String path) {
if (path.equals(labelZnode) || path.equals(userAuthsZnode)) {
try {
- watcher.sync(path);
+ watcher.syncOrTimeout(path);
byte[] data = ZKUtil.getDataAndWatch(watcher, path);
if (path.equals(labelZnode)) {
refreshVisibilityLabelsCache(data);
diff --git a/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java b/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
index f8c9a3f..d5be759 100644
--- a/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
+++ b/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
@@ -728,7 +728,7 @@ public class RecoverableZooKeeper {
}
public void sync(String path, AsyncCallback.VoidCallback cb, Object ctx) throws KeeperException {
- checkZk().sync(path, cb, null);
+ checkZk().sync(path, cb, ctx);
}
/**
diff --git a/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKWatcher.java b/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKWatcher.java
index 9774a51..fca8738 100644
--- a/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKWatcher.java
+++ b/hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKWatcher.java
@@ -23,13 +23,20 @@ import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.AuthUtil;
+import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.ZooKeeperConnectionException;
import org.apache.hadoop.hbase.security.Superusers;
+import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
+import org.apache.hadoop.hbase.util.Threads;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.zookeeper.KeeperException;
@@ -79,8 +86,22 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
// listeners to be notified
private final List<ZKListener> listeners = new CopyOnWriteArrayList<>();
+ // Single threaded executor pool that processes event notifications from Zookeeper. Events are
+ // processed in the order in which they arrive (pool backed by an unbounded fifo queue). We do
+ // this to decouple the event processing from Zookeeper's ClientCnxn's EventThread context.
+ // EventThread internally runs a single while loop to serially process all the events. When events
+ // are processed by the listeners in the same thread, that blocks the EventThread from processing
+ // subsequent events. Processing events in a separate thread frees up the event thread to continue
+ // and further prevents deadlocks if the process method itself makes other zookeeper calls.
+ // It is ok to do it in a single thread because the Zookeeper ClientCnxn already serializes the
+ // requests using a single while loop and hence there is no performance degradation.
+ private final ExecutorService zkEventProcessor =
+ Executors.newSingleThreadExecutor(Threads.getNamedThreadFactory("zk-event-processor"));
+
private final Configuration conf;
+ private final long zkSyncTimeout;
+
/* A pattern that matches a Kerberos name, borrowed from Hadoop's KerberosName */
private static final Pattern NAME_PATTERN = Pattern.compile("([^/@]*)(/([^/@]*))?@([^/@]*)");
@@ -169,6 +190,8 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
throw zce;
}
}
+ this.zkSyncTimeout = conf.getLong(HConstants.ZK_SYNC_BLOCKING_TIMEOUT_MS,
+ HConstants.ZK_SYNC_BLOCKING_TIMEOUT_DEFAULT_MS);
}
private void createBaseZNodes() throws ZooKeeperConnectionException {
@@ -479,21 +502,8 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
return znodePaths;
}
- /**
- * Method called from ZooKeeper for events and connection status.
- * <p>
- * Valid events are passed along to listeners. Connection status changes
- * are dealt with locally.
- */
- @Override
- public void process(WatchedEvent event) {
- LOG.debug(prefix("Received ZooKeeper Event, " +
- "type=" + event.getType() + ", " +
- "state=" + event.getState() + ", " +
- "path=" + event.getPath()));
-
+ private void processEvent(WatchedEvent event) {
switch(event.getType()) {
-
// If event type is NONE, this is a connection status change
case None: {
connectionEvent(event);
@@ -501,7 +511,6 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
}
// Otherwise pass along to the listeners
-
case NodeCreated: {
for(ZKListener listener : listeners) {
listener.nodeCreated(event.getPath());
@@ -530,10 +539,26 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
break;
}
default:
- throw new IllegalStateException("Received event is not valid: " + event.getState());
+ LOG.error("Invalid event of type {} received for path {}. Ignoring.",
+ event.getState(), event.getPath());
}
}
+ /**
+ * Method called from ZooKeeper for events and connection status.
+ * <p>
+ * Valid events are passed along to listeners. Connection status changes
+ * are dealt with locally.
+ */
+ @Override
+ public void process(WatchedEvent event) {
+ LOG.debug(prefix("Received ZooKeeper Event, " +
+ "type=" + event.getType() + ", " +
+ "state=" + event.getState() + ", " +
+ "path=" + event.getPath()));
+ zkEventProcessor.submit(() -> processEvent(event));
+ }
+
// Connection management
/**
@@ -585,7 +610,8 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
}
/**
- * Forces a synchronization of this ZooKeeper client connection.
+ * Forces a synchronization of this ZooKeeper client connection within a timeout. Enforcing a
+ * timeout lets the callers fail-fast rather than wait forever for the sync to finish.
* <p>
* Executing this method before running other methods will ensure that the
* subsequent operations are up-to-date and consistent as of the time that
@@ -595,9 +621,28 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
* data of an existing node and delete or transition that node, utilizing the
* previously read version and data. We want to ensure that the version read
* is up-to-date from when we begin the operation.
+ * <p>
*/
- public void sync(String path) throws KeeperException {
- this.recoverableZooKeeper.sync(path, null, null);
+ public void syncOrTimeout(String path) throws KeeperException {
+ final CountDownLatch latch = new CountDownLatch(1);
+ long startTime = EnvironmentEdgeManager.currentTime();
+ this.recoverableZooKeeper.sync(path, (i, s, o) -> latch.countDown(), null);
+ try {
+ if (!latch.await(zkSyncTimeout, TimeUnit.MILLISECONDS)) {
+ LOG.warn("sync() operation to ZK timed out. Configured timeout: {}ms. This usually points "
+ + "to a ZK side issue. Check ZK server logs and metrics.", zkSyncTimeout);
+ throw new KeeperException.RequestTimeoutException();
+ }
+ } catch (InterruptedException e) {
+ LOG.warn("Interrupted waiting for ZK sync() to finish.", e);
+ Thread.currentThread().interrupt();
+ return;
+ }
+ if (LOG.isDebugEnabled()) {
+ // TODO: Switch to a metric once server side ZK watcher metrics are implemented. This is a
+ // useful metric to have since the latency of sync() impacts the callers.
+ LOG.debug("ZK sync() operation took {}ms", EnvironmentEdgeManager.currentTime() - startTime);
+ }
}
/**
@@ -647,6 +692,7 @@ public class ZKWatcher implements Watcher, Abortable, Closeable {
*/
@Override
public void close() {
+ zkEventProcessor.shutdownNow();
try {
recoverableZooKeeper.close();
} catch (InterruptedException e) {