[GitHub] [hbase] anmolnar commented on a diff in pull request #4869: HBASE-27347 Port FileWatcher from ZK to autodetect keystore/truststore changes in TLS connections

[GitBox <gi...@apache.org>]

anmolnar commented on code in PR #4869:
URL: https://github.com/apache/hbase/pull/4869#discussion_r1018053827


##########
hbase-common/src/main/java/org/apache/hadoop/hbase/io/FileChangeWatcher.java:
##########
@@ -0,0 +1,251 @@
+/*
+ * 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.hadoop.hbase.io;
+
+import java.io.IOException;
+import java.nio.file.ClosedWatchServiceException;
+import java.nio.file.FileSystem;
+import java.nio.file.Path;
+import java.nio.file.StandardWatchEventKinds;
+import java.nio.file.WatchEvent;
+import java.nio.file.WatchKey;
+import java.nio.file.WatchService;
+import java.util.function.Consumer;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.zookeeper.server.ZooKeeperThread;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Instances of this class can be used to watch a directory for file changes. When a file is added
+ * to, deleted from, or is modified in the given directory, the callback provided by the user will
+ * be called from a background thread. Some things to keep in mind:
+ * <ul>
+ * <li>The callback should be thread-safe.</li>
+ * <li>Changes that happen around the time the thread is started may be missed.</li>
+ * <li>There is a delay between a file changing and the callback firing.</li>
+ * <li>The watch is not recursive - changes to subdirectories will not trigger a callback.</li>
+ * </ul>
+ * <p/>
+ * This file has been copied from the Apache ZooKeeper project.
+ * @see <a href=
+ *      "https://github.com/apache/zookeeper/blob/8148f966947d3ecf3db0b756d93c9ffa88174af9/zookeeper-server/src/main/java/org/apache/zookeeper/common/FileChangeWatcher.java">Base
+ *      revision</a>
+ */
+@InterfaceAudience.Private
+public final class FileChangeWatcher {

Review Comment:
   Urm... I don't have a strong opinion. We were following this pattern in the entire implementation of TLS. It's probably better to stay on the safe side and avoid sideeffects in ZK non-backward compatible changes. They're quite unlikely though.



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscribe@hbase.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org