From b108d11d3d758bd4c8cc906ce0316b1c2c42c38f Mon Sep 17 00:00:00 2001 From: Bharath Vissapragada Date: Thu, 25 Jun 2020 13:27:38 -0700 Subject: [PATCH] HBASE-24603: Make Zookeeper sync() call synchronous (#1945) 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 Signed-off-by: Viraj Jasani (cherry picked from commit 84e246f9b197bfa4307172db5465214771b78d38) (cherry picked from commit 2379a25f0c4f2bdd3ea91fa5e0ba63f034c8d21c) --- .../hbase/zookeeper/RecoverableZooKeeper.java | 2 +- .../hadoop/hbase/zookeeper/ZKAssign.java | 10 +- .../hbase/zookeeper/ZooKeeperWatcher.java | 101 ++++++++++++++---- .../org/apache/hadoop/hbase/HConstants.java | 9 ++ .../backup/example/HFileArchiveManager.java | 4 +- .../visibility/ZKVisibilityLabelWatcher.java | 2 +- .../apache/hadoop/hbase/master/Mocking.java | 2 +- .../TestSplitTransactionOnCluster.java | 4 +- 8 files changed, 99 insertions(+), 35 deletions(-) diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java index 6c29fcce3ab7..c5ecae945254 100644 --- a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java +++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java @@ -875,7 +875,7 @@ public synchronized byte[] getSessionPasswd() { } 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-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKAssign.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKAssign.java index b2e1e1eeb15f..59d2f1308d4a 100644 --- a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKAssign.java +++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKAssign.java @@ -208,7 +208,7 @@ public static int createOrForceNodeOffline(ZooKeeperWatcher zkw, region.getRegionName(), serverName, HConstants.EMPTY_BYTE_ARRAY); byte [] data = rt.toByteArray(); String node = getNodeName(zkw, region.getEncodedName()); - zkw.sync(node); + zkw.syncOrTimeout(node); int version = ZKUtil.checkExists(zkw, node); if (version == -1) { return ZKUtil.createAndWatch(zkw, node, data); @@ -444,7 +444,7 @@ public static boolean deleteNode(ZooKeeperWatcher zkw, String encodedRegionName, "node " + encodedRegionName + " in expected state " + expectedState)); } String node = getNodeName(zkw, encodedRegionName); - zkw.sync(node); + zkw.syncOrTimeout(node); Stat stat = new Stat(); byte [] bytes = ZKUtil.getDataNoWatch(zkw, node, stat); if (bytes == null) { @@ -645,7 +645,7 @@ public static int confirmNodeOpening(ZooKeeperWatcher zkw, } String node = getNodeName(zkw, encoded); - zkw.sync(node); + zkw.syncOrTimeout(node); // Read existing data of the node Stat stat = new Stat(); @@ -727,7 +727,7 @@ public static boolean checkClosingState(ZooKeeperWatcher zkw, HRegionInfo region int expectedVersion) throws KeeperException { final String encoded = getNodeName(zkw, region.getEncodedName()); - zkw.sync(encoded); + zkw.syncOrTimeout(encoded); // Read existing data of the node Stat stat = new Stat(); @@ -807,7 +807,7 @@ public static int transitionNode(ZooKeeperWatcher zkw, HRegionInfo region, } String node = getNodeName(zkw, encoded); - zkw.sync(node); + zkw.syncOrTimeout(node); // Read existing data of the node Stat stat = new Stat(); diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java index 0b4e84872d78..6e80432bf06d 100644 --- a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java +++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWatcher.java @@ -26,6 +26,9 @@ import java.util.Map; 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; @@ -38,9 +41,11 @@ import org.apache.hadoop.hbase.HConstants; import org.apache.hadoop.hbase.HRegionInfo; import org.apache.hadoop.hbase.ZooKeeperConnectionException; -import org.apache.hadoop.hbase.classification.InterfaceAudience; 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.zookeeper.AsyncCallback; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; @@ -86,6 +91,18 @@ public class ZooKeeperWatcher implements Watcher, Abortable, Closeable { private final List 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")); + // Used by ZKUtil:waitForZKConnectionIfAuthenticating to wait for SASL // negotiation to complete public CountDownLatch saslLatch = new CountDownLatch(1); @@ -143,6 +160,8 @@ public class ZooKeeperWatcher implements Watcher, Abortable, Closeable { 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("([^/@]*)(/([^/@]*))?@([^/@]*)"); @@ -196,6 +215,8 @@ public ZooKeeperWatcher(Configuration conf, String identifier, throw zce; } } + this.zkSyncTimeout = conf.getLong(HConstants.ZK_SYNC_BLOCKING_TIMEOUT_MS, + HConstants.ZK_SYNC_BLOCKING_TIMEOUT_DEFAULT_MS); } private void createBaseZNodes() throws ZooKeeperConnectionException { @@ -609,59 +630,66 @@ public String getBaseZNode() { return baseZNode; } - /** - * Method called from ZooKeeper for events and connection status. - *

- * 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); break; } - // Otherwise pass along to the listeners - case NodeCreated: { for(ZooKeeperListener listener : listeners) { listener.nodeCreated(event.getPath()); } break; } - case NodeDeleted: { for(ZooKeeperListener listener : listeners) { listener.nodeDeleted(event.getPath()); } break; } - case NodeDataChanged: { for(ZooKeeperListener listener : listeners) { listener.nodeDataChanged(event.getPath()); } break; } - case NodeChildrenChanged: { for(ZooKeeperListener listener : listeners) { listener.nodeChildrenChanged(event.getPath()); } break; } + default: { + LOG.error(String.format("Invalid event of type %s received for path %s. Ignoring", + event.getType(), event.getPath())); + break; + } } } + /** + * Method called from ZooKeeper for events and connection status. + *

+ * Valid events are passed along to listeners. Connection status changes + * are dealt with locally. + */ + @Override + public void process(final WatchedEvent event) { + LOG.debug(prefix("Received ZooKeeper Event, " + + "type=" + event.getType() + ", " + + "state=" + event.getState() + ", " + + "path=" + event.getPath())); + zkEventProcessor.submit(new Runnable() { + @Override + public void run() { + processEvent(event); + } + }); + } + // Connection management /** @@ -709,7 +737,8 @@ private void connectionEvent(WatchedEvent event) { } /** - * 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. *

* Executing this method before running other methods will ensure that the * subsequent operations are up-to-date and consistent as of the time that @@ -720,8 +749,33 @@ private void connectionEvent(WatchedEvent event) { * previously read version and data. We want to ensure that the version read * is up-to-date from when we begin the operation. */ - 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, new AsyncCallback.VoidCallback() { + @Override + public void processResult(int i, String s, Object o) { + latch.countDown(); + } + }, null); + try { + if (!latch.await(zkSyncTimeout, TimeUnit.MILLISECONDS)) { + LOG.warn(String.format("sync() operation to ZK timed out. Configured timeout: %s ms. " + + "This usually points to a ZK side issue. Check ZK server logs and metrics.", + zkSyncTimeout)); + throw new KeeperException.OperationTimeoutException(); + } + } 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(String.format("ZK sync() operation took %d ms", + EnvironmentEdgeManager.currentTime() - startTime)); + } } /** @@ -770,6 +824,7 @@ public void interruptedExceptionNoThrow(InterruptedException ie, boolean throwLa */ @Override public void close() { + zkEventProcessor.shutdownNow(); try { recoverableZooKeeper.close(); } catch (InterruptedException e) { 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 4607de986a06..9c5dd1d4787b 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 @@ -244,6 +244,15 @@ public enum OperationStatusCode { /** 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 = 180 * 1000; 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 85b1135a0ff8..80f4dc6bee15 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 @@ -123,7 +123,7 @@ private void enable(ZooKeeperWatcher zooKeeper, byte[] table) */ private void disable(ZooKeeperWatcher 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) { @@ -132,7 +132,7 @@ private void disable(ZooKeeperWatcher zooKeeper, byte[] table) throws KeeperExce // 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 4941a54aec98..cb71b88b8110 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 @@ -109,7 +109,7 @@ public void nodeDeleted(String path) { 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-server/src/test/java/org/apache/hadoop/hbase/master/Mocking.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/master/Mocking.java index fefcaf53f6c3..0b0a3849db3f 100644 --- a/hbase-server/src/test/java/org/apache/hadoop/hbase/master/Mocking.java +++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/master/Mocking.java @@ -71,7 +71,7 @@ static boolean verifyRegionState(ZooKeeperWatcher zkw, HRegionInfo region, Event String encoded = region.getEncodedName(); String node = ZKAssign.getNodeName(zkw, encoded); - zkw.sync(node); + zkw.syncOrTimeout(node); // Read existing data of the node byte [] existingBytes = null; diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java index 15c51eb533de..2c664933d759 100644 --- a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java +++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java @@ -1087,7 +1087,7 @@ public void testSplitWithRegionReplicas() throws Exception { assertTrue("not able to find a splittable region", region != null); String node = ZKAssign.getNodeName(regionServer.getZooKeeper(), region.getRegionInfo().getEncodedName()); - regionServer.getZooKeeper().sync(node); + regionServer.getZooKeeper().syncOrTimeout(node); SplitTransactionImpl st = new SplitTransactionImpl(region, Bytes.toBytes("row2")); try { st.prepare(); @@ -1318,7 +1318,7 @@ public PairOfSameType stepsBeforePONR(final Server server, }; String node = ZKAssign.getNodeName(regionServer.getZooKeeper(), region.getRegionInfo().getEncodedName()); - regionServer.getZooKeeper().sync(node); + regionServer.getZooKeeper().syncOrTimeout(node); for (int i = 0; i < 100; i++) { // We expect the znode to be deleted by this time. Here the // znode could be in OPENED state and the