LUCENE-2104: Fix NativeFSLock.release() to throw exception if lock is held by another thread/process.

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@891205 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -57,6 +57,9 @@ Bug fixes
 * LUCENE-2166: Don't incorrectly keep warning about the same immense
   term, when IndexWriter.infoStream is on.  (Mike McCandless)
 
+* LUCENE-2104: NativeFSLock.release() would silently fail if the lock is held by 
+  another thread/process.  (Shai Erera via Uwe Schindler)
+  
 New features
 
 * LUCENE-2128: Parallelized fetching document frequencies during weight

src/java/org/apache/lucene/store/NativeFSLockFactory.java

@@ -146,7 +146,7 @@ public class NativeFSLockFactory extends FSLockFactory {
       }
     }
   }
-};
+}
 
 class NativeFSLock extends Lock {
 
@@ -300,6 +300,24 @@ class NativeFSLock extends Lock {
       }
       if (!path.delete())
         throw new LockReleaseFailedException("failed to delete " + path);
+    } else {
+      // if we don't hold the lock, and somebody still called release(), for
+      // example as a result of calling IndexWriter.unlock(), we should attempt
+      // to obtain the lock and release it. If the obtain fails, it means the
+      // lock cannot be released, and we should throw a proper exception rather
+      // than silently failing/not doing anything.
+      boolean obtained = false;
+      try {
+        if (!(obtained = obtain())) {
+          throw new LockReleaseFailedException(
+              "Cannot forcefully unlock a NativeFSLock which is held by another indexer component: "
+                  + path);
+        }
+      } finally {
+        if (obtained) {
+          release();
+        }
+      }
     }
   }
 

src/test/org/apache/lucene/store/TestLockFactory.java

@@ -198,6 +198,26 @@ public class TestLockFactory extends LuceneTestCase {
       assertFalse(l2.isLocked());
     }
 
+    public void testNativeFSLockReleaseByOtherLock() throws IOException {
+
+      NativeFSLockFactory f = new NativeFSLockFactory(System.getProperty("tempDir"));
+
+      f.setLockPrefix("test");
+      Lock l = f.makeLock("commit");
+      Lock l2 = f.makeLock("commit");
+
+      assertTrue("failed to obtain lock", l.obtain());
+      try {
+        assertTrue(l2.isLocked());
+        l2.release();
+        fail("should not have reached here. LockReleaseFailedException should have been thrown");
+      } catch (IOException e) {
+        assertTrue("Unexpected exception", e instanceof LockReleaseFailedException);
+      } finally {
+        l.release();
+      }
+    }
+
     // Verify: NativeFSLockFactory assigns null as lockPrefix if the lockDir is inside directory
     public void testNativeFSLockFactoryPrefix() throws IOException {