Call session aware createEphemeral to create live instance. (#700)
Live instance creation is still using the old API createEphemeral(path, data) without the session ID, resulting in zk session race condition being not completely fixed.
So this commit changes the api to use createEphemeral(path, data, sessionId) for zk session validation and live instance creation. A new unit test is also added to cover session expiry in participant manager when creating live instance.
diff --git a/helix-core/src/main/java/org/apache/helix/manager/zk/ParticipantManager.java b/helix-core/src/main/java/org/apache/helix/manager/zk/ParticipantManager.java
index 2e10f8f..7af69c6 100644
--- a/helix-core/src/main/java/org/apache/helix/manager/zk/ParticipantManager.java
+++ b/helix-core/src/main/java/org/apache/helix/manager/zk/ParticipantManager.java
@@ -201,7 +201,8 @@
do {
retry = false;
try {
- _zkclient.createEphemeral(liveInstancePath, liveInstance.getRecord());
+ // Zk session ID will be validated in createEphemeral.
+ _zkclient.createEphemeral(liveInstancePath, liveInstance.getRecord(), _sessionId);
LOG.info("LiveInstance created, path: {}, sessionId: {}", liveInstancePath,
liveInstance.getEphemeralOwner());
} catch (ZkSessionMismatchedException e) {
@@ -243,7 +244,8 @@
*/
if (retry) {
try {
- _zkclient.createEphemeral(liveInstancePath, liveInstance.getRecord());
+ // Zk session ID will be validated in createEphemeral.
+ _zkclient.createEphemeral(liveInstancePath, liveInstance.getRecord(), _sessionId);
LOG.info("LiveInstance created, path: {}, sessionId: {}", liveInstancePath,
liveInstance.getEphemeralOwner());
} catch (ZkSessionMismatchedException e) {
diff --git a/helix-core/src/test/java/org/apache/helix/manager/zk/TestParticipantManager.java b/helix-core/src/test/java/org/apache/helix/manager/zk/TestParticipantManager.java
new file mode 100644
index 0000000..a03f4f2
--- /dev/null
+++ b/helix-core/src/test/java/org/apache/helix/manager/zk/TestParticipantManager.java
@@ -0,0 +1,184 @@
+package org.apache.helix.manager.zk;
+
+/*
+ * 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.
+ */
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Semaphore;
+
+import org.apache.helix.PreConnectCallback;
+import org.apache.helix.PropertyKey;
+import org.apache.helix.TestHelper;
+import org.apache.helix.ZkTestHelper;
+import org.apache.helix.common.ZkTestBase;
+import org.apache.helix.integration.manager.MockParticipantManager;
+import org.apache.helix.model.LiveInstance;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+
+public class TestParticipantManager extends ZkTestBase {
+ private static Logger LOG = LoggerFactory.getLogger(TestParticipantManager.class);
+
+ /*
+ * Simulates zk session expiry before creating live instance in participant manager. This test
+ * makes sure the session aware create ephemeral API is called, which validates the expected zk
+ * session.
+ * What this test does is:
+ * 1. Sets up live instance with session S0
+ * 2. Expires S0 and gets new session S1
+ * 3. S1 is blocked before creating live instance in participant manager
+ * 4. Expires S1 and gets new session S2
+ * 5. Proceeds S1 to create live instance, which will fail because session S1 is expired
+ * 6. Proceeds S2 to create live instance, which will succeed
+ */
+ @Test
+ public void testSessionExpiryCreateLiveInstance() throws Exception {
+ final String className = TestHelper.getTestClassName();
+ final String methodName = TestHelper.getTestMethodName();
+ final String clusterName = className + "_" + methodName;
+
+ final ZKHelixDataAccessor accessor =
+ new ZKHelixDataAccessor(clusterName, new ZkBaseDataAccessor<>(ZK_ADDR));
+ final PropertyKey.Builder keyBuilder = accessor.keyBuilder();
+
+ TestHelper.setupCluster(clusterName, ZK_ADDR,
+ 12918, // participant port
+ "localhost", // participant name prefix
+ "TestDB", // resource name prefix
+ 1, // resources
+ 10, // partitions per resource
+ 5, // number of nodes
+ 3, // replicas
+ "MasterSlave",
+ true); // do rebalance
+
+ final String instanceName = "localhost_12918";
+ final MockParticipantManager manager =
+ new MockParticipantManager(ZK_ADDR, clusterName, instanceName);
+
+ manager.syncStart();
+
+ final LiveInstance liveInstance = accessor.getProperty(keyBuilder.liveInstance(instanceName));
+ final long originalCreationTime = liveInstance.getStat().getCreationTime();
+ final String originalSessionId = manager.getSessionId();
+
+ // Verify current live instance.
+ Assert.assertNotNull(liveInstance);
+ Assert.assertEquals(liveInstance.getEphemeralOwner(), originalSessionId);
+
+ final CountDownLatch startCountdown = new CountDownLatch(1);
+ final CountDownLatch endCountdown = new CountDownLatch(1);
+ final Semaphore semaphore = new Semaphore(0);
+ manager.addPreConnectCallback(
+ new BlockingPreConnectCallback(instanceName, startCountdown, endCountdown, semaphore));
+
+ // Expire S0 and new session S1 will be created.
+ ZkTestHelper.asyncExpireSession(manager.getZkClient());
+
+ // Wait for onPreConnect to start
+ semaphore.acquire();
+
+ // New session S1 should not be equal to S0.
+ Assert.assertFalse(originalSessionId.equals(manager.getSessionId()));
+
+ // Live instance should be gone as original session S0 is expired.
+ Assert.assertNull(accessor.getProperty(keyBuilder.liveInstance(instanceName)));
+
+ final String sessionOne = manager.getSessionId();
+
+ // Expire S1 when S1 is blocked in onPreConnect().
+ // New session S2 will be created.
+ ZkTestHelper.asyncExpireSession(manager.getZkClient());
+
+ TestHelper.verify(
+ () -> !(ZKUtil.toHexSessionId(manager.getZkClient().getSessionId()).equals(sessionOne)),
+ TestHelper.WAIT_DURATION);
+
+ // New session S2 should not be equal to S1.
+ final String sessionTwo = ZKUtil.toHexSessionId(manager.getZkClient().getSessionId());
+ Assert.assertFalse(sessionOne.equals(sessionTwo));
+
+ // Proceed S1 to create live instance, which will fail.
+ startCountdown.countDown();
+
+ // Wait until S2 starts onPreConnect, which indicates S1's handling new session is completed.
+ semaphore.acquire();
+
+ // Live instance should not be created because zk session is expired.
+ Assert.assertNull(accessor.getProperty(keyBuilder.liveInstance(instanceName)),
+ "Live instance should not be created because zk session is expired!");
+
+ // Proceed S2 to create live instance.
+ endCountdown.countDown();
+
+ TestHelper.verify(() -> {
+ // Newly created live instance should be created by the latest session S2
+ // and have a new creation time.
+ LiveInstance newLiveInstance =
+ accessor.getProperty(keyBuilder.liveInstance(instanceName));
+ return newLiveInstance != null
+ && newLiveInstance.getStat().getCreationTime() != originalCreationTime
+ && newLiveInstance.getEphemeralOwner().equals(sessionTwo);
+ }, TestHelper.WAIT_DURATION);
+
+ // Clean up.
+ manager.syncStop();
+ deleteCluster(clusterName);
+ }
+
+ /*
+ * Mocks PreConnectCallback to insert session expiry during ParticipantManager#handleNewSession()
+ */
+ static class BlockingPreConnectCallback implements PreConnectCallback {
+ private final String instanceName;
+ private final CountDownLatch startCountDown;
+ private final CountDownLatch endCountDown;
+ private final Semaphore semaphore;
+
+ private boolean canCreateLiveInstance;
+
+ BlockingPreConnectCallback(String instanceName, CountDownLatch startCountdown,
+ CountDownLatch endCountdown, Semaphore semaphore) {
+ this.instanceName = instanceName;
+ this.startCountDown = startCountdown;
+ this.endCountDown = endCountdown;
+ this.semaphore = semaphore;
+ }
+
+ @Override
+ public void onPreConnect() {
+ LOG.info("Handling new session for instance: {}", instanceName);
+ semaphore.release();
+ try {
+ LOG.info("Waiting session expiry to happen.");
+ startCountDown.await();
+ if (canCreateLiveInstance) {
+ LOG.info("Waiting to continue creating live instance.");
+ endCountDown.await();
+ }
+ } catch (InterruptedException ex) {
+ LOG.error("Interrupted in waiting", ex);
+ }
+ canCreateLiveInstance = true;
+ }
+ }
+}
