ZOOKEEPER-1781. ZooKeeper Server fails if snapCount is set to 1 (Takashi Ohnishi via phunt, breed)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/trunk@1530108 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -429,6 +429,9 @@ BUGFIXES:
   ZOOKEEPER-1551. Observers ignore txns that come after snapshot and UPTODATE 
   (thawan, fpj via thawan)
 
+  ZOOKEEPER-1781. ZooKeeper Server fails if snapCount is set to 1
+  (Takashi Ohnishi via phunt, breed)
+
 IMPROVEMENTS:
 
   ZOOKEEPER-1170. Fix compiler (eclipse) warnings: unused imports,

docs/zookeeperAdmin.html

@@ -1074,10 +1074,13 @@ server.3=zoo3:2888:3888</pre>
 <dd>
 <p>(Java system property: <strong>zookeeper.snapCount</strong>)</p>
 <p>ZooKeeper logs transactions to a transaction
-              log. After snapCount transactions are written to a log
-              file a snapshot is started and a new transaction log
-              file is created. The default snapCount is
-              100,000.</p>
+              log. SnapCount defines a timing when a snapshot is started
+              and a new transaction logfile is created. A random number
+              between snapCount/2 and snapCount-1 is chosen and when the
+              number of transactions becomes bigger than it, ZooKeeper
+              server starts a snapshot. This prevents that all the ZooKeeper
+              servers in the ensemble start a snapshot at the same time.
+              The default snapCount is 100,000.</p>
 </dd>
 
           

src/java/main/org/apache/zookeeper/server/ZooKeeperServer.java

@@ -668,7 +668,14 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
     public static int getSnapCount() {
         String sc = System.getProperty("zookeeper.snapCount");
         try {
-            return Integer.parseInt(sc);
+            int snapCount = Integer.parseInt(sc);
+
+            // snapCount must be 2 or more. See org.apache.zookeeper.server.SyncRequestProcessor
+            if( snapCount < 2 ) {
+                LOG.warn("SnapCount should be 2 or more. Now, snapCount is reset to 2");
+                snapCount = 2;
+            }
+            return snapCount;
         } catch (Exception e) {
             return 100000;
         }

src/java/test/org/apache/zookeeper/server/InvalidSnapCountTest.java

@@ -0,0 +1,126 @@
+/**
+ * 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;
+
+import static org.apache.zookeeper.test.ClientBase.CONNECTION_TIMEOUT;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.zookeeper.WatchedEvent;
+import org.apache.zookeeper.Watcher;
+import org.apache.zookeeper.ZKTestCase;
+import org.apache.zookeeper.ZooKeeper;
+import org.apache.zookeeper.test.ClientBase;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test stand-alone server.
+ *
+ */
+public class InvalidSnapCountTest extends ZKTestCase implements Watcher {
+    protected static final Logger LOG =
+        LoggerFactory.getLogger(InvalidSnapCountTest.class);
+
+    public static class MainThread extends Thread {
+        final File confFile;
+        final TestMain main;
+
+        public MainThread(int clientPort) throws IOException {
+            super("Standalone server with clientPort:" + clientPort);
+            File tmpDir = ClientBase.createTmpDir();
+            confFile = new File(tmpDir, "zoo.cfg");
+
+            FileWriter fwriter = new FileWriter(confFile);
+            fwriter.write("tickTime=2000\n");
+            fwriter.write("initLimit=10\n");
+            fwriter.write("syncLimit=5\n");
+            fwriter.write("snapCount=1\n");
+
+            File dataDir = new File(tmpDir, "data");
+            if (!dataDir.mkdir()) {
+                throw new IOException("unable to mkdir " + dataDir);
+            }
+            
+            // Convert windows path to UNIX to avoid problems with "\"
+            String dir = dataDir.toString();
+            String osname = java.lang.System.getProperty("os.name");
+            if (osname.toLowerCase().contains("windows")) {
+                dir = dir.replace('\\', '/');
+            }
+            fwriter.write("dataDir=" + dir + "\n");
+            
+            fwriter.write("clientPort=" + clientPort + "\n");
+            fwriter.flush();
+            fwriter.close();
+
+            main = new TestMain();
+        }
+
+        public void run() {
+            String args[] = new String[1];
+            args[0] = confFile.toString();
+            try {
+                main.initializeAndRun(args);
+            } catch (Exception e) {
+                // test will still fail even though we just log/ignore
+                LOG.error("unexpected exception in run", e);
+            }
+        }
+
+        public void shutdown() {
+            main.shutdown();
+        }
+    }
+
+    public static  class TestMain extends ZooKeeperServerMain {
+        public void shutdown() {
+            super.shutdown();
+        }
+    }
+
+    /**
+     * Verify the ability to start a standalone server instance.
+     */
+    @Test
+    public void testInvalidSnapCount() throws Exception {
+
+        final int CLIENT_PORT = 3181;
+
+        MainThread main = new MainThread(CLIENT_PORT);
+        main.start();
+
+        Assert.assertTrue("waiting for server being up",
+                ClientBase.waitForServerUp("127.0.0.1:" + CLIENT_PORT,
+                        CONNECTION_TIMEOUT));
+
+        Assert.assertEquals(SyncRequestProcessor.getSnapCount(), 2);
+
+        main.shutdown();
+
+    }
+
+    public void process(WatchedEvent event) {
+        // ignore for this test
+    }
+}