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https://issues.apache.org/jira/browse/GIRAPH-1188?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16452579#comment-16452579
]
ASF GitHub Bot commented on GIRAPH-1188:
----------------------------------------
Github user dlogothetis commented on a diff in the pull request:
https://github.com/apache/giraph/pull/70#discussion_r184121699
--- Diff:
giraph-core/src/main/java/org/apache/giraph/writable/kryo/GiraphClassResolver.java
---
@@ -0,0 +1,308 @@
+/*
+ * 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.giraph.writable.kryo;
+import com.esotericsoftware.kryo.Kryo;
+import com.esotericsoftware.kryo.KryoException;
+import com.esotericsoftware.kryo.Registration;
+import com.esotericsoftware.kryo.io.Input;
+import com.esotericsoftware.kryo.io.Output;
+import com.esotericsoftware.kryo.util.DefaultClassResolver;
+import com.esotericsoftware.kryo.util.ObjectMap;
+import org.apache.giraph.zk.ZooKeeperExt;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.ZooDefs;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.List;
+
+import static com.esotericsoftware.kryo.util.Util.getWrapperClass;
+
+/**
+ * This class resolver assigns unique classIds for every class that was not
+ * explicitly registered. It uses zookeeper for consistent mapping across
all
+ * nodes.
+ */
+public class GiraphClassResolver extends DefaultClassResolver {
+ /** Length of the ZK sequence number */
+ private static final int SEQUENCE_NUMBER_LENGTH = 10;
+ /** Base ID to start for class name assignments.
+ * This number has to be high enough to not conflict with
+ * explicity registered class IDs.
+ * */
+ private static final int BASE_CLASS_ID = 10000;
+
+ /** Class name to ID cache */
+ private static Map<String, Integer> CLASS_NAME_TO_ID = new HashMap();
+ /** ID to class name cache */
+ private static Map<Integer, String> ID_TO_CLASS_NAME = new HashMap();
+ /** Zookeeper */
+ private static ZooKeeperExt ZK;
+ /** Zookeeper path for automatic class registrations */
+ private static String KRYO_REGISTERED_CLASS_PATH;
+ /** Minimum class ID assigned by zookeeper sequencing */
+ private static int MIN_CLASS_ID = -1;
+
+ /** Memoized class id*/
+ private int memoizedClassId = -1;
+ /** Memoized class registration */
+ private Registration memoizedClassIdValue;
+
+ /**
+ * Sets zookeeper informaton.
+ * @param zookeeperExt ZookeeperExt
+ * @param kryoClassPath Zookeeper directory path where class Name-ID
+ * mapping is stored.
+ */
+ public static void setZookeeperInfo(ZooKeeperExt zookeeperExt,
+ String kryoClassPath) {
+ ZK = zookeeperExt;
+ KRYO_REGISTERED_CLASS_PATH = kryoClassPath;
+ }
+
+ /**
+ * Creates a new node for the given class name.
+ * Creation mode is persistent sequential, i.e.
+ * ZK will always create a new node . There could be
+ * multiple entries for the same class name but since
+ * the lowest index is used, this is not a problem.
+ * @param className Class name
+ */
+ public static void createClassName(String className) {
+ try {
+ String path = KRYO_REGISTERED_CLASS_PATH + "/" + className;
+ ZK.createExt(path,
+ null,
+ ZooDefs.Ids.OPEN_ACL_UNSAFE,
+ CreateMode.PERSISTENT_SEQUENTIAL,
+ true);
+ } catch (KeeperException e) {
+ throw new IllegalStateException(
+ "Failed to create class " + className, e);
+ } catch (InterruptedException e) {
+ throw new IllegalStateException(
+ "Interrupted while creating " + className, e);
+ }
+ }
+
+ /**
+ * Refreshes class-ID mapping from zookeeper.
+ * Not thread safe.
+ */
+ public static void refreshCache() {
+ try {
+ ZK.createOnceExt(KRYO_REGISTERED_CLASS_PATH,
+ null,
+ ZooDefs.Ids.OPEN_ACL_UNSAFE,
+ CreateMode.PERSISTENT,
+ true);
+ } catch (KeeperException e) {
+ throw new IllegalStateException(
+ "Failed to refresh kryo cache " +
+ KRYO_REGISTERED_CLASS_PATH, e);
+ } catch (InterruptedException e) {
+ throw new IllegalStateException(
+ "Interrupted while refreshing kryo cache " +
+ KRYO_REGISTERED_CLASS_PATH, e);
+ }
+
+ List<String> registeredList;
+ try {
+ registeredList =
+ ZK.getChildrenExt(KRYO_REGISTERED_CLASS_PATH,
+ false,
+ true,
+ false);
+ } catch (KeeperException e) {
+ throw new IllegalStateException(
+ "Failed to retrieve child nodes for " +
KRYO_REGISTERED_CLASS_PATH, e);
+ } catch (InterruptedException e) {
+ throw new IllegalStateException(
+ "Interrupted while retrieving child nodes for " +
+ KRYO_REGISTERED_CLASS_PATH, e);
+ }
+
+ for (String name : registeredList) {
+ String className = name.substring(0,
+ name.length() - SEQUENCE_NUMBER_LENGTH);
+ int classId = Integer.parseInt(
+ name.substring(name.length() - SEQUENCE_NUMBER_LENGTH));
+
+ if (MIN_CLASS_ID == -1) {
+ MIN_CLASS_ID = classId;
+ }
+
+ int adjustedId = classId - MIN_CLASS_ID + BASE_CLASS_ID;
+ if (CLASS_NAME_TO_ID.putIfAbsent(className, adjustedId) == null) {
+ ID_TO_CLASS_NAME.put(adjustedId, className);
+ }
+ }
+ }
+
+ /**
+ * Gets ID for the given class name.
+ * @param className Class name
+ * @return class id Class ID
+ */
+ public static int getClassId(String className) {
+ if (CLASS_NAME_TO_ID.containsKey(className)) {
+ return CLASS_NAME_TO_ID.get(className);
+ }
+ synchronized (GiraphClassResolver.class) {
+ if (CLASS_NAME_TO_ID.containsKey(className)) {
+ return CLASS_NAME_TO_ID.get(className);
+ }
+ refreshCache();
+
+ if (!CLASS_NAME_TO_ID.containsKey(className)) {
+ createClassName(className);
+ refreshCache();
+ }
+ }
+
+ if (!CLASS_NAME_TO_ID.containsKey(className)) {
+ throw new IllegalStateException("Failed to assigned id to " +
className);
+ }
+
+ return CLASS_NAME_TO_ID.get(className);
+ }
+
+ /**
+ * Get class name for given ID.
+ * @param id class ID
+ * @return class name
+ */
+ public static String getClassName(int id) {
+ if (ID_TO_CLASS_NAME.containsKey(id)) {
+ return ID_TO_CLASS_NAME.get(id);
+ }
+ synchronized (GiraphClassResolver.class) {
+ if (ID_TO_CLASS_NAME.containsKey(id)) {
+ return ID_TO_CLASS_NAME.get(id);
+ }
+ refreshCache();
+ }
+
+ if (!ID_TO_CLASS_NAME.containsKey(id)) {
+ throw new IllegalStateException("ID " + id + " doesn't exist");
+ }
+ return ID_TO_CLASS_NAME.get(id);
+ }
+
+ @Override
+ public Registration register(Registration registration) {
+ if (registration == null) {
+ throw new IllegalArgumentException("registration cannot be null");
+ }
+ if (registration.getId() == NAME) {
+ throw new IllegalArgumentException("Invalid registration ID");
+ }
+
+ idToRegistration.put(registration.getId(), registration);
+ classToRegistration.put(registration.getType(), registration);
+ if (registration.getType().isPrimitive()) {
+ classToRegistration.put(getWrapperClass(registration.getType()),
+ registration);
+ }
+ return registration;
+ }
+
+ @Override
+ public Registration registerImplicit(Class type) {
+ return register(new Registration(type, kryo.getDefaultSerializer(type),
+ getClassId(type.getName())));
+ }
+
+ @Override
+ public Registration writeClass(Output output, Class type) {
+ if (type == null) {
+ output.writeVarInt(Kryo.NULL, true);
+ return null;
+ }
+
+ Registration registration = kryo.getRegistration(type);
+ if (registration.getId() == NAME) {
+ throw new IllegalStateException("Invalid registration ID");
+ } else {
+ output.writeVarInt(registration.getId() + 2, true);
--- End diff --
Can we add this as a comment here?
> Add kryo custom class resolver for faster serialization.
> --------------------------------------------------------
>
> Key: GIRAPH-1188
> URL: https://issues.apache.org/jira/browse/GIRAPH-1188
> Project: Giraph
> Issue Type: Improvement
> Reporter: Yuksel Akinci
> Priority: Major
>
> The custom class resolver allows kryo to always use the integer IDs for
> classes that are agreed by all nodes running the job. Default class resolver
> always writes the full class name of the first encountered class type to the
> stream, and then it assigns an integer for subsequent instances. These
> changes make the serialization faster by eliminating the need to write the
> full name for the first encountered class instance.
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