HBASE-23106 [HBCK2/hbase-operator-tools] Add a WAL verifier

Adds simple WALReader.

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/handler/OpenRegionHandler.java

@@ -302,7 +302,7 @@ public boolean progress() {
       // and transition the node back to FAILED_OPEN. If that fails,
       // we rely on the Timeout Monitor in the master to reassign.
       LOG.error(
-          "Failed open of region=" + this.regionInfo.getRegionNameAsString(), t);
+          "Failed open of {}", this.regionInfo.getRegionNameAsString(), t);
     }
     return region;
   }

hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALReader.java

@@ -0,0 +1,67 @@
+/*
+ *
+ * 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.wal;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HBaseConfiguration;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+import org.apache.yetus.audience.InterfaceAudience;
+
+import java.io.IOException;
+
+/**
+ * Read the passed in WAL passed on command-line (or recovered.edits file since it has same
+ * format). Stamps out offset, key, and value size of edit seen. Use to verify WAL or
+ * recovered.edits files.
+ */
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.TOOLS)
+public class WALReader {
+  private static void read(WALFactory factory, FileSystem fs, Path path) throws IOException {
+    System.out.println(path.toString());
+    try (WAL.Reader reader = factory.createReader(fs, path)) {
+      WAL.Entry entry = new WAL.Entry();
+      while((entry = reader.next(entry)) != null) {
+        System.out.println(reader.getPosition() + " " + entry.getKey().toString() +
+            " " + entry.getEdit().estimatedSerializedSizeOf());
+      }
+    }
+  }
+
+  public static void main(String [] args) throws IOException {
+    if (args.length < 1) {
+      System.err.println("Usage: WALReader <FILE> [<FILE>...]");
+      return;
+    }
+    Configuration configuration = HBaseConfiguration.create();
+    FileSystem fs = FileSystem.get(configuration);
+    WALFactory factory = null;
+    try {
+      factory = WALFactory.getInstance(configuration);
+      for (String p: args) {
+        read(factory, fs, new Path(p));
+      }
+    } finally {
+      if (factory != null) {
+        factory.close();
+      }
+    }
+  }
+}

src/main/asciidoc/_chapters/ops_mgt.adoc

@@ -879,6 +879,15 @@ The output can optionally be mapped to another set of tables.
 
 WALPlayer can also generate HFiles for later bulk importing, in that case only a single table and no mapping can be specified.
 
+.WALReader
+[NOTE]
+====
+Since hbase-2.3.0/2.2.2/2.1.8, a WALReader tool has been added. Pass it WALs or recovered.edits files,
+which are of the same format, and it will read the content spitting out offset, key names, and size
+of edit. Useful looking at content or just verifying a file readable.
+====
+
+
 Invoke via:
 
 ----