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https://issues.apache.org/jira/browse/ZOOKEEPER-2959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16438510#comment-16438510
]
ASF GitHub Bot commented on ZOOKEEPER-2959:
-------------------------------------------
Github user eribeiro commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/500#discussion_r181266640
--- Diff: src/java/test/org/apache/zookeeper/server/quorum/ZabUtils.java ---
@@ -0,0 +1,140 @@
+/**
+ * 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.zookeeper.server.quorum;
+
+import org.apache.zookeeper.PortAssignment;
+import org.apache.zookeeper.server.ServerCnxn;
+import org.apache.zookeeper.server.ServerCnxnFactory;
+import org.apache.zookeeper.server.ZKDatabase;
+import org.apache.zookeeper.server.ZooKeeperServer;
+import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
+import org.apache.zookeeper.server.quorum.flexible.QuorumMaj;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.net.InetSocketAddress;
+import java.util.HashMap;
+
+public class ZabUtils {
+ public static final int SYNC_LIMIT = 2;
+
--- End diff --
If this is a helper class that doesn't require instantiation then create a
private constructor: this makes it "final" and prevents instantiation.
> ignore accepted epoch and LEADERINFO ack from observers when a newly elected
> leader computes new epoch
> ------------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-2959
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2959
> Project: ZooKeeper
> Issue Type: Bug
> Affects Versions: 3.4.10, 3.5.3
> Reporter: xiangyq000
> Assignee: Bogdan Kanivets
> Priority: Blocker
>
> Once the ZooKeeper cluster finishes the election for new leader, all learners
> report their accepted epoch to the leader for the computation of new cluster
> epoch.
> org.apache.zookeeper.server.quorum.Leader#getEpochToPropose
> {code:java}
> private final HashSet<Long> connectingFollowers = new HashSet<Long>();
> public long getEpochToPropose(long sid, long lastAcceptedEpoch) throws
> InterruptedException, IOException {
> synchronized(connectingFollowers) {
> if (!waitingForNewEpoch) {
> return epoch;
> }
> if (lastAcceptedEpoch >= epoch) {
> epoch = lastAcceptedEpoch+1;
> }
> connectingFollowers.add(sid);
> QuorumVerifier verifier = self.getQuorumVerifier();
> if (connectingFollowers.contains(self.getId()) &&
>
> verifier.containsQuorum(connectingFollowers)) {
> waitingForNewEpoch = false;
> self.setAcceptedEpoch(epoch);
> connectingFollowers.notifyAll();
> } else {
> long start = Time.currentElapsedTime();
> long cur = start;
> long end = start + self.getInitLimit()*self.getTickTime();
> while(waitingForNewEpoch && cur < end) {
> connectingFollowers.wait(end - cur);
> cur = Time.currentElapsedTime();
> }
> if (waitingForNewEpoch) {
> throw new InterruptedException("Timeout while waiting for
> epoch from quorum");
> }
> }
> return epoch;
> }
> }
> {code}
> The computation will get an outcome once :
> # The leader has call method "getEpochToPropose"
> # The number of all reporters is greater than half of participants.
> The problem is, an observer server will also send its accepted epoch to the
> leader, while this procedure treat observers as participants.
> Supposed that the cluster consists of 1 leader, 2 followers and 1 observer,
> and now the leader and the observer have reported their accepted epochs while
> neither of the followers has. Thus, the connectingFollowers set consists of
> two elements, resulting in a size of 2, which is greater than half quorum,
> namely, 2. Then QuorumVerifier#containsQuorum will return true, because it
> does not check whether the elements of the parameter are participants.
> The same flaw exists in
> org.apache.zookeeper.server.quorum.Leader#waitForEpochAck
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