ZOOKEEPER-1875: NullPointerException in ClientCnxn$EventThread.processEvent

Author: Mohammad Arshad <arshad@apache.org>

Reviewers: Mate Szalay-Beko <symat@apache.org>, Enrico Olivelli <eolivelli@apache.org>

Closes #1855 from arshadmohammad/ZOOKEEPER-1875-npe and squashes the following commits:

4a7d471e3 [Mohammad Arshad] Corrected impacted test cases
12f44d62e [Mohammad Arshad] ZOOKEEPER-1875: NullPointerException in ClientCnxn$EventThread.processEvent

4 files changed, 92 insertions, 13 deletions

diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/ZooKeeper.java b/zookeeper-server/src/main/java/org/apache/zookeeper/ZooKeeper.java
index 127f5a2a3..281355b1a 100644
--- a/zookeeper-server/src/main/java/org/apache/zookeeper/ZooKeeper.java
+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/ZooKeeper.java
@@ -442,7 +442,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(String connectString, int sessionTimeout, Watcher watcher) throws IOException {
         this(connectString, sessionTimeout, watcher, false);
@@ -491,7 +496,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -556,7 +566,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -624,7 +639,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -640,6 +660,7 @@ public class ZooKeeper implements AutoCloseable {
             sessionTimeout,
             watcher);
 
+        validateWatcher(watcher);
         this.clientConfig = clientConfig != null ? clientConfig : new ZKClientConfig();
         this.hostProvider = hostProvider;
         ConnectStringParser connectStringParser = new ConnectStringParser(connectString);
@@ -724,7 +745,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -786,7 +812,12 @@ public class ZooKeeper implements AutoCloseable {
      * @throws IOException
      *             in cases of network failure
      * @throws IllegalArgumentException
-     *             if an invalid chroot path is specified
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -852,8 +883,13 @@ public class ZooKeeper implements AutoCloseable {
      *            password for this session
      *
      * @throws IOException in cases of network failure
-     * @throws IllegalArgumentException if an invalid chroot path is specified
-     * @throws IllegalArgumentException for an invalid list of ZooKeeper hosts
+     * @throws IllegalArgumentException
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -926,7 +962,13 @@ public class ZooKeeper implements AutoCloseable {
      * @param aHostProvider
      *            use this as HostProvider to enable custom behaviour.
      * @throws IOException in cases of network failure
-     * @throws IllegalArgumentException if an invalid chroot path is specified
+     * @throws IllegalArgumentException
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -1013,7 +1055,12 @@ public class ZooKeeper implements AutoCloseable {
      *            configuring properties differently compared to other instances
      * @throws IOException in cases of network failure
      * @throws IllegalArgumentException if an invalid chroot path is specified
-     *
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      * @since 3.5.5
      */
     public ZooKeeper(
@@ -1034,6 +1081,7 @@ public class ZooKeeper implements AutoCloseable {
             Long.toHexString(sessionId),
             (sessionPasswd == null ? "<null>" : "<hidden>"));
 
+        validateWatcher(watcher);
         this.clientConfig = clientConfig != null ? clientConfig : new ZKClientConfig();
         ConnectStringParser connectStringParser = new ConnectStringParser(connectString);
         this.hostProvider = hostProvider;
@@ -1111,7 +1159,13 @@ public class ZooKeeper implements AutoCloseable {
      *            allowed while write requests are not. It continues seeking for
      *            majority in the background.
      * @throws IOException in cases of network failure
-     * @throws IllegalArgumentException if an invalid chroot path is specified
+     * @throws IllegalArgumentException
+     *             if any of the following is true:
+     *             <ul>
+     *             <li> if an invalid chroot path is specified
+     *             <li> for an invalid list of ZooKeeper hosts
+     *             <li> watcher is null
+     *             </ul>
      */
     public ZooKeeper(
         String connectString,
@@ -1194,8 +1248,10 @@ public class ZooKeeper implements AutoCloseable {
     /**
      * Specify the default watcher for the connection (overrides the one
      * specified during construction).
+     * @throws IllegalArgumentException if watcher is null
      */
     public synchronized void register(Watcher watcher) {
+        validateWatcher(watcher);
         getWatchManager().setDefaultWatcher(watcher);
     }
 
diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/ZooKeeperTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/ZooKeeperTest.java
index c829e85da..9d45802bb 100644
--- a/zookeeper-server/src/test/java/org/apache/zookeeper/ZooKeeperTest.java
+++ b/zookeeper-server/src/test/java/org/apache/zookeeper/ZooKeeperTest.java
@@ -815,4 +815,27 @@ public class ZooKeeperTest extends ClientBase {
         assertThrows(IllegalArgumentException.class, () -> KeeperException.create(Code.get(Integer.MAX_VALUE)));
     }
 
+    @Test
+    public void testInvalidWatcherRegistration() throws Exception {
+        String nullWatcherMsg = "Invalid Watcher, shouldn't be null!";
+        final ZooKeeper zk = createClient();
+        try {
+            zk.register(null);
+            fail("Should validate null watcher!");
+        } catch (IllegalArgumentException iae) {
+            assertEquals(nullWatcherMsg, iae.getMessage());
+        }
+        try {
+            new ZooKeeper(hostPort, 10000, null, false);
+            fail("Should validate null watcher!");
+        } catch (IllegalArgumentException iae) {
+            assertEquals(nullWatcherMsg, iae.getMessage());
+        }
+        try {
+            new ZooKeeper(hostPort, 10000, null, 10L, "".getBytes(), false);
+            fail("Should validate null watcher!");
+        } catch (IllegalArgumentException iae) {
+            assertEquals(nullWatcherMsg, iae.getMessage());
+        }
+    }
 }
diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/QuorumDigestTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/QuorumDigestTest.java
index af2fed8cf..a9e65a445 100644
--- a/zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/QuorumDigestTest.java
+++ b/zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/QuorumDigestTest.java
@@ -204,7 +204,7 @@ public class QuorumDigestTest extends QuorumPeerTestBase {
 
     private void triggerOps(int sid, String prefix) throws Exception {
         TxnLogDigestTest.performOperations(servers.zk[sid], prefix);
-        servers.restartClient(sid, null);
+        servers.restartClient(sid, event -> { });
         waitForOne(servers.zk[sid], States.CONNECTED);
     }
 
diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/test/ObserverMasterTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/test/ObserverMasterTest.java
index 4ba33c7a8..ab30a1de0 100644
--- a/zookeeper-server/src/test/java/org/apache/zookeeper/test/ObserverMasterTest.java
+++ b/zookeeper-server/src/test/java/org/apache/zookeeper/test/ObserverMasterTest.java
@@ -213,7 +213,7 @@ public class ObserverMasterTest extends ObserverMasterTestBase {
     public void testInOrderCommits(boolean testObserverMaster) throws Exception {
         setUp(-1, testObserverMaster);
 
-        zk = new ZooKeeper("127.0.0.1:" + CLIENT_PORT_QP1, ClientBase.CONNECTION_TIMEOUT, null);
+        zk = new ZooKeeper("127.0.0.1:" + CLIENT_PORT_QP1, ClientBase.CONNECTION_TIMEOUT, event -> { });
         for (int i = 0; i < 10; i++) {
             zk.create("/bulk"
                               + i, ("Initial data of some size").getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);