[GitHub] [hbase] Apache9 commented on a change in pull request #3679: HBASE-26267 Don't try to recover WALs from a WAL dir which doesn't exist

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

Apache9 commented on a change in pull request #3679:
URL: https://github.com/apache/hbase/pull/3679#discussion_r726241962



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File path: hbase-server/src/main/java/org/apache/hadoop/hbase/master/region/MasterRegion.java
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@@ -227,7 +227,31 @@ private static HRegion open(Configuration conf, TableDescriptor td, FileSystem f
     if (!walFs.exists(replayEditsDir) && !walFs.mkdirs(replayEditsDir)) {
       throw new IOException("Failed to create replay directory: " + replayEditsDir);
     }
+
+    // Replay any WALs for the Master Region before opening it.
     Path walsDir = new Path(walRootDir, HREGION_LOGDIR_NAME);
+    // In open(...), we expect that the WAL directory for the MasterRegion to already exist.
+    // This is in contrast to bootstrap() where we create the MasterRegion data and WAL dir.
+    // However, it's possible that users directly remove the WAL directory. We expect walsDir
+    // to always exist in normal situations, but we should guard against users changing the
+    // filesystem outside of HBase's line of sight.
+    if (walFs.exists(walsDir)) {
+      replayWALs(conf, walFs, walRootDir, walsDir, regionInfo, serverName, replayEditsDir);
+    } else {
+      LOG.warn("UNEXPECTED: WAL directory for MasterRegion is missing."

Review comment:
       Better use LOG.error here and say it may cause data loss? In general, removing directories directly outside the HBase control is a dangerous operation...




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