https://issues.apache.org/jira/browse/AMQ-4705 - apply patch from ganesh murthy with thanks. Fix and test making use of last modified to track deletion and recreation events

activemq-broker/src/main/java/org/apache/activemq/util/LockFile.java

@@ -16,11 +16,15 @@
  */
 package org.apache.activemq.util;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.File;
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.channels.FileLock;
 import java.nio.channels.OverlappingFileLockException;
+import java.util.Calendar;
 import java.util.Date;
 
 /**
@@ -32,6 +36,7 @@ public class LockFile {
 
     private static final boolean DISABLE_FILE_LOCK = Boolean.getBoolean("java.nio.channels.FileLock.broken");
     final private File file;
+    private long lastModified;
 
     private FileLock lock;
     private RandomAccessFile readFile;
@@ -39,6 +44,8 @@ public class LockFile {
     private final boolean deleteOnUnlock;
     private volatile boolean locked;
 
+    private static final Logger LOG = LoggerFactory.getLogger(LockFile.class);
+
     public LockFile(File file, boolean deleteOnUnlock) {
         this.file = file;
         this.deleteOnUnlock = deleteOnUnlock;
@@ -75,6 +82,8 @@ public class LockFile {
                     reason = ioe;
                 }
                 if (lock != null) {
+                    //Set lastModified only if we are able to successfully obtain the lock.
+                    lastModified = file.lastModified();
                     lockCounter++;
                     System.setProperty(getVmLockKey(), new Date().toString());
                     locked = true;
@@ -138,11 +147,34 @@ public class LockFile {
             }
             readFile = null;
         }
+    }
 
+    /**
+     * @return true if the lock file's last modified does not match the locally cached lastModified, false otherwise
+     */
+    private boolean hasBeenModified() {
+        boolean modified = false;
+
+        //Create a new instance of the File object so we can get the most up to date information on the file.
+        File localFile = new File(file.getAbsolutePath());
+
+        if (localFile.exists()) {
+            if(localFile.lastModified() != lastModified) {
+                LOG.info("Lock file " + file.getAbsolutePath() + ", locked at " + new Date(lastModified) + ", has been modified at " + new Date(localFile.lastModified()));
+                modified = true;
+            }
+        }
+        else {
+            //The lock file is missing
+            LOG.info("Lock file " + file.getAbsolutePath() + ", does not exist");
+            modified = true;
+        }
+
+        return modified;
     }
 
     public boolean keepAlive() {
-        locked = locked && lock != null && lock.isValid() && file.exists();
+        locked = locked && lock != null && lock.isValid() && !hasBeenModified();
         return locked;
     }
 

activemq-unit-tests/src/test/java/org/apache/activemq/store/kahadb/KahaDBDeleteLockTest.java

@@ -0,0 +1,108 @@
+/**
+ * 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.activemq.store.kahadb;
+
+import org.apache.activemq.broker.BrokerService;
+import org.apache.activemq.util.Wait;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.RandomAccessFile;
+import java.util.concurrent.TimeUnit;
+
+
+import static org.junit.Assert.assertTrue;
+
+public class KahaDBDeleteLockTest {
+
+    protected BrokerService master;
+
+    protected KahaDBPersistenceAdapter masterPersistenceAdapter = new KahaDBPersistenceAdapter();
+
+    private final File testDataDir = new File("target/activemq-data/KahaDBDeleteLockTest");
+    private final File kahaDataDir = new File(testDataDir, "kahadb");
+
+    @Before
+    public void createMaster() throws Exception{
+        master = new BrokerService();
+        master.setBrokerName("Master");
+        master.setDataDirectoryFile(testDataDir);
+
+        masterPersistenceAdapter.setDirectory(kahaDataDir);
+        masterPersistenceAdapter.setLockKeepAlivePeriod(500);
+
+        master.setPersistenceAdapter(masterPersistenceAdapter);
+        master.start();
+        master.waitUntilStarted();
+    }
+
+    @After
+    public void stopBrokerJustInCase() throws Exception {
+        if (master != null) {
+            master.stop();
+        }
+    }
+
+    /**
+     * Deletes the lock file and makes sure that the broken stops.
+     * @throws Exception
+     */
+    @Test
+    public void testLockFileDelete() throws Exception {
+        assertTrue(master.isStarted());
+
+        //Delete the lock file
+        File lockFile = new File(kahaDataDir, "lock");
+
+        if(lockFile.exists()) {
+            lockFile.delete();
+        }
+
+        assertTrue("Master stops on lock file delete", Wait.waitFor(new Wait.Condition() {
+            @Override
+            public boolean isSatisified() throws Exception {
+                return master.isStopped();
+            }
+        }));
+    }
+
+    /**
+     * Modifies the lock file so that the last modified date is not the same when the broker obtained the lock.
+     * This should force the broker to stop.
+     * @throws Exception
+     */
+    @Test
+    public void testModifyLockFile() throws Exception {
+        assertTrue(master.isStarted());
+
+        // ensure modification will be seen, milisecond granularity
+        TimeUnit.MILLISECONDS.sleep(1);
+        RandomAccessFile file = new RandomAccessFile(new File(kahaDataDir, "lock"), "rw");
+        file.write(4);
+        file.close();
+
+        assertTrue("Master stops on lock file modification", Wait.waitFor(new Wait.Condition() {
+            @Override
+            public boolean isSatisified() throws Exception {
+                return master.isStopped();
+            }
+        }, 5000));
+
+    }
+}