HBASE-21843 RegionGroupingProvider breaks the meta wal file name pattern which may cause data loss for meta region

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

@@ -145,15 +145,21 @@ public class RegionGroupingProvider implements WALProvider {
     }
     this.conf = conf;
     this.factory = factory;
-    StringBuilder sb = new StringBuilder().append(factory.factoryId);
-    if (providerId != null) {
-      if (providerId.startsWith(WAL_FILE_NAME_DELIMITER)) {
-        sb.append(providerId);
-      } else {
-        sb.append(WAL_FILE_NAME_DELIMITER).append(providerId);
+
+    if (META_WAL_PROVIDER_ID.equals(providerId)) {
+      // do not change the provider id if it is for meta
+      this.providerId = providerId;
+    } else {
+      StringBuilder sb = new StringBuilder().append(factory.factoryId);
+      if (providerId != null) {
+        if (providerId.startsWith(WAL_FILE_NAME_DELIMITER)) {
+          sb.append(providerId);
+        } else {
+          sb.append(WAL_FILE_NAME_DELIMITER).append(providerId);
+        }
       }
+      this.providerId = sb.toString();
     }
-    this.providerId = sb.toString();
     this.strategy = getStrategy(conf, REGION_GROUPING_STRATEGY, DEFAULT_REGION_GROUPING_STRATEGY);
     this.providerClass = factory.getProviderClass(DELEGATE_PROVIDER, DEFAULT_DELEGATE_PROVIDER);
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/wal/TestWrongMetaWALFileName.java

@@ -0,0 +1,73 @@
+/**
+ * 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 static org.junit.Assert.assertTrue;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.regionserver.HRegionServer;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.testclassification.RegionServerTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+/**
+ * Testcase for HBASE-21843. Used to confirm that we use the correct name for meta wal file when
+ * using {@link RegionGroupingProvider}.
+ */
+@Category({ RegionServerTests.class, MediumTests.class })
+public class TestWrongMetaWALFileName {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestWrongMetaWALFileName.class);
+
+  private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
+
+  @BeforeClass
+  public static void setUp() throws Exception {
+    UTIL.getConfiguration().set(WALFactory.WAL_PROVIDER, WALFactory.Providers.multiwal.name());
+    UTIL.startMiniCluster(1);
+  }
+
+  @AfterClass
+  public static void tearDown() throws Exception {
+    UTIL.shutdownMiniCluster();
+  }
+
+  @Test
+  public void test() throws Exception {
+    // create a table so that we will write some edits to meta
+    TableName tableName = TableName.valueOf("whatever");
+    UTIL.createTable(tableName, Bytes.toBytes("family"));
+    UTIL.waitTableAvailable(tableName);
+    HRegionServer rs = UTIL.getMiniHBaseCluster().getRegionServer(0);
+    Path walDir = new Path(rs.getWALRootDir(),
+      AbstractFSWALProvider.getWALDirectoryName(rs.getServerName().toString()));
+    // we should have meta wal files.
+    assertTrue(
+      rs.getWALFileSystem().listStatus(walDir, AbstractFSWALProvider::isMetaFile).length > 0);
+  }
+}