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Subject [GitHub] [zookeeper] hanm commented on a change in pull request #632: [ZOOKEEPER-3150] Add tree digest check and verify data integrity when loading from disk
Date Sat, 27 Jul 2019 23:47:36 GMT
hanm commented on a change in pull request #632: [ZOOKEEPER-3150] Add tree digest check and
verify data integrity when loading from disk
URL: https://github.com/apache/zookeeper/pull/632#discussion_r307979780
 
 

 ##########
 File path: zookeeper-server/src/main/java/org/apache/zookeeper/server/util/DigestCalculator.java
 ##########
 @@ -0,0 +1,145 @@
+/**
+ * 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.util;
+
+import java.nio.ByteBuffer;
+import java.util.zip.CRC32;
+
+import org.apache.zookeeper.ZooDefs;
+import org.apache.zookeeper.data.StatPersisted;
+import org.apache.zookeeper.server.DataNode;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Defines how to calculate the digest for a given node.
+ */
+public class DigestCalculator {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DigestCalculator.class);
+
+    // The hardcoded digest version, should bump up this version whenever
+    // we changed the digest method or fields.
+    //
+    // Defined it as Integer to make it able to be changed in test via reflection
+    public static final Integer DIGEST_VERSION = 2;
+
+    public static final String ZOOKEEPER_DIGEST_ENABLED = "zookeeper.digest.enabled";
+    private static boolean digestEnabled = true;
+
+    static {
+        digestEnabled = Boolean.parseBoolean(
+                System.getProperty(ZOOKEEPER_DIGEST_ENABLED, "true"));
+        LOG.info("{} = {}", ZOOKEEPER_DIGEST_ENABLED, digestEnabled);
+    }
+
+    /**
+     * Calculate the digest based on the given params.
+     *
+     * Besides the path and data, the following stat fields are included in
+     * the digest calculation:
+     *
+     * - long czxid    8 bytes
+     * - long mzxid    8 bytes
+     * - long pzxid    8 bytes
+     * - long ctime    8 bytes
+     * - long mtime    8 bytes
+     * - int version   4 bytes
+     * - int cversion  4 bytes
+     * - int aversion  4 bytes
+     * - long ephemeralOwner 8 bytes
+     *
+     * @param path the path of the node
+     * @param data the data of the node
+     * @param stat the stat associated with the node
+     * @return the digest calculated from the given params
+     */
+    public static long calculateDigest(String path, byte[] data, StatPersisted stat) {
+
+        if (!digestEnabled()) {
+            return 0;
+        }
+
+        // Quota nodes are updated locally, there is inconsistent issue
+        // when we tried to release digest feature at the beginning.
+        //
+        // Instead of taking time to fix that, we decided to disable digest
+        // check for all the nodes under /zookeeper/ first.
+        //
+        // We can enable this after fixing that inconsistent problem. The
+        // digest version in the protocol enables us to change the digest
+        // calculation without disrupting the system.
+        if (path.startsWith(ZooDefs.ZOOKEEPER_NODE_SUBTREE)) {
+            return 0;
+        }
+
+        // "" and "/" are aliase to each other, in DataTree when adding child
 
 Review comment:
   nit: typo `alias`

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