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From se...@apache.org
Subject [2/4] flink git commit: [FLINK-5408] [RocksDB backend] Uniquify RocksDB JNI library path to avoid multiple classloader problem
Date Thu, 05 Jan 2017 19:38:21 GMT
[FLINK-5408] [RocksDB backend] Uniquify RocksDB JNI library path to avoid multiple classloader
problem


Project: http://git-wip-us.apache.org/repos/asf/flink/repo
Commit: http://git-wip-us.apache.org/repos/asf/flink/commit/91f9a1ac
Tree: http://git-wip-us.apache.org/repos/asf/flink/tree/91f9a1ac
Diff: http://git-wip-us.apache.org/repos/asf/flink/diff/91f9a1ac

Branch: refs/heads/release-1.2
Commit: 91f9a1acaa899159a0d907528634bd246e6854b4
Parents: 9c0c19a
Author: Stephan Ewen <sewen@apache.org>
Authored: Thu Jan 5 00:18:13 2017 +0100
Committer: Stephan Ewen <sewen@apache.org>
Committed: Thu Jan 5 17:34:13 2017 +0100

----------------------------------------------------------------------
 .../streaming/state/RocksDBStateBackend.java    |  29 ++++--
 .../state/RocksDbMultiClassLoaderTest.java      | 100 +++++++++++++++++++
 .../runtime/state/StateBackendTestBase.java     |   3 +-
 3 files changed, 123 insertions(+), 9 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/flink/blob/91f9a1ac/flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBStateBackend.java
----------------------------------------------------------------------
diff --git a/flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBStateBackend.java
b/flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBStateBackend.java
index 2109cea..c2e33d4 100644
--- a/flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBStateBackend.java
+++ b/flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBStateBackend.java
@@ -30,6 +30,7 @@ import org.apache.flink.runtime.state.CheckpointStreamFactory;
 import org.apache.flink.runtime.state.KeyGroupRange;
 import org.apache.flink.runtime.state.KeyGroupsStateHandle;
 import org.apache.flink.runtime.state.filesystem.FsStateBackend;
+import org.apache.flink.util.AbstractID;
 
 import org.rocksdb.ColumnFamilyOptions;
 import org.rocksdb.DBOptions;
@@ -70,8 +71,10 @@ public class RocksDBStateBackend extends AbstractStateBackend {
 
 	private static final Logger LOG = LoggerFactory.getLogger(RocksDBStateBackend.class);
 
+	/** The number of (re)tries for loading the RocksDB JNI library */
 	private static final int ROCKSDB_LIB_LOADING_ATTEMPTS = 3;
 
+	
 	private static boolean rocksDbInitialized = false;
 
 	// ------------------------------------------------------------------------
@@ -476,24 +479,34 @@ public class RocksDBStateBackend extends AbstractStateBackend {
 	// ------------------------------------------------------------------------
 
 	private void ensureRocksDBIsLoaded(String tempDirectory) throws Exception {
-		// lock on something that cannot be in the user JAR
-		synchronized (org.apache.flink.runtime.taskmanager.Task.class) {
+		synchronized (RocksDBStateBackend.class) {
 			if (!rocksDbInitialized) {
 
-				final File tempDirFile = new File(tempDirectory);
-				final String path = tempDirFile.getAbsolutePath();
-
-				LOG.info("Attempting to load RocksDB native library and store it at '{}'", path);
+				final File tempDirParent = new File(tempDirectory).getAbsoluteFile();
+				LOG.info("Attempting to load RocksDB native library and store it under '{}'", tempDirParent);
 
 				Throwable lastException = null;
 				for (int attempt = 1; attempt <= ROCKSDB_LIB_LOADING_ATTEMPTS; attempt++) {
 					try {
+						// when multiple instances of this class and RocksDB exist in different
+						// class loaders, then we can see the following exception:
+						// "java.lang.UnsatisfiedLinkError: Native Library /path/to/temp/dir/librocksdbjni-linux64.so
+						// already loaded in another class loader"
+
+						// to avoid that, we need to add a random element to the library file path
+						// (I know, seems like an unnecessary hack, since the JVM obviously can handle multiple
+						//  instances of the same JNI library being loaded in different class loaders, but
+						//  apparently not when coming from the same file path, so there we go)
+
+						final File rocksLibFolder = new File(tempDirParent, "rocksdb-lib-" + new AbstractID());
+
 						// make sure the temp path exists
+						LOG.debug("Attempting to create RocksDB native library folder {}", rocksLibFolder);
 						// noinspection ResultOfMethodCallIgnored
-						tempDirFile.mkdirs();
+						rocksLibFolder.mkdirs();
 
 						// explicitly load the JNI dependency if it has not been loaded before
-						NativeLibraryLoader.getInstance().loadLibrary(path);
+						NativeLibraryLoader.getInstance().loadLibrary(rocksLibFolder.getAbsolutePath());
 
 						// this initialization here should validate that the loading succeeded
 						RocksDB.loadLibrary();

http://git-wip-us.apache.org/repos/asf/flink/blob/91f9a1ac/flink-contrib/flink-statebackend-rocksdb/src/test/java/org/apache/flink/contrib/streaming/state/RocksDbMultiClassLoaderTest.java
----------------------------------------------------------------------
diff --git a/flink-contrib/flink-statebackend-rocksdb/src/test/java/org/apache/flink/contrib/streaming/state/RocksDbMultiClassLoaderTest.java
b/flink-contrib/flink-statebackend-rocksdb/src/test/java/org/apache/flink/contrib/streaming/state/RocksDbMultiClassLoaderTest.java
new file mode 100644
index 0000000..c53fa3e
--- /dev/null
+++ b/flink-contrib/flink-statebackend-rocksdb/src/test/java/org/apache/flink/contrib/streaming/state/RocksDbMultiClassLoaderTest.java
@@ -0,0 +1,100 @@
+/*
+ * 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.flink.contrib.streaming.state;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.rocksdb.RocksDB;
+
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+import static org.junit.Assert.*;
+
+/**
+ * This test validates that the RocksDB JNI library loading works properly
+ * in the presence of the RocksDB code being loaded dynamically via reflection.
+ * That can happen when RocksDB is in the user code JAR, or in certain test setups.
+ */
+public class RocksDbMultiClassLoaderTest {
+
+	@Rule
+	public final TemporaryFolder tmp = new TemporaryFolder();
+
+	@Test
+	public void testTwoSeparateClassLoaders() throws Exception {
+		// collect the libraries / class folders with RocksDB related code: the state backend and
RocksDB itself
+		final URL codePath1 = RocksDBStateBackend.class.getProtectionDomain().getCodeSource().getLocation();
+		final URL codePath2 = RocksDB.class.getProtectionDomain().getCodeSource().getLocation();
+
+		final ClassLoader parent = getClass().getClassLoader();
+		final ClassLoader loader1 = new ChildFirstClassLoader(new URL[] { codePath1, codePath2
}, parent);
+		final ClassLoader loader2 = new ChildFirstClassLoader(new URL[] { codePath1, codePath2
}, parent);
+
+		final String className = RocksDBStateBackend.class.getName();
+
+		final Class<?> clazz1 = Class.forName(className, false, loader1);
+		final Class<?> clazz2 = Class.forName(className, false, loader2);
+		assertNotEquals("Test broken - the two reflectively loaded classes are equal", clazz1,
clazz2);
+
+		final Object instance1 = clazz1.getConstructor(String.class).newInstance(tmp.newFolder().toURI().toString());
+		final Object instance2 = clazz2.getConstructor(String.class).newInstance(tmp.newFolder().toURI().toString());
+
+		final String tempDir = tmp.newFolder().getAbsolutePath();
+
+ 		final Method meth1 = clazz1.getDeclaredMethod("ensureRocksDBIsLoaded", String.class);
+		final Method meth2 = clazz2.getDeclaredMethod("ensureRocksDBIsLoaded", String.class);
+		meth1.setAccessible(true);
+		meth2.setAccessible(true);
+
+		// if all is well, these methods can both complete successfully
+		meth1.invoke(instance1, tempDir);
+		meth2.invoke(instance2, tempDir);
+	}
+
+	// ------------------------------------------------------------------------
+
+	/**
+	 * A variant of the URLClassLoader that first loads from the URLs and only after that from
the parent.
+	 */
+	private static final class ChildFirstClassLoader extends URLClassLoader {
+
+		private final ClassLoader parent;
+
+		public ChildFirstClassLoader(URL[] urls, ClassLoader parent) {
+			super(urls, null);
+			this.parent = parent;
+		}
+
+		@Override
+		public Class<?> findClass(String name) throws ClassNotFoundException {
+			// first try to load from the URLs
+			// because the URLClassLoader's parent is null, this cannot implicitly load from the parent
+			try {
+				return super.findClass(name);
+			}
+			catch (ClassNotFoundException e) {
+				// not in the URL, check the parent
+				return parent.loadClass(name);
+			}
+		}
+	}
+}

http://git-wip-us.apache.org/repos/asf/flink/blob/91f9a1ac/flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
----------------------------------------------------------------------
diff --git a/flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
b/flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
index aad84df..5655f1c 100644
--- a/flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
+++ b/flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
@@ -48,6 +48,7 @@ import org.apache.flink.runtime.query.netty.message.KvStateRequestSerializer;
 import org.apache.flink.runtime.state.heap.AbstractHeapState;
 import org.apache.flink.runtime.state.heap.StateTable;
 import org.apache.flink.types.IntValue;
+import org.apache.flink.util.TestLogger;
 import org.junit.Test;
 
 import java.util.Collections;
@@ -68,7 +69,7 @@ import static org.mockito.Mockito.verify;
  * Generic tests for the partitioned state part of {@link AbstractStateBackend}.
  */
 @SuppressWarnings("serial")
-public abstract class StateBackendTestBase<B extends AbstractStateBackend> {
+public abstract class StateBackendTestBase<B extends AbstractStateBackend> extends
TestLogger {
 
 	protected abstract B getStateBackend() throws Exception;
 


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