[jira] [Created] (HBASE-9270) [0.94] FSTableDescriptors caching is racy

["Andrew Purtell (JIRA)" <ji...@apache.org>]

Andrew Purtell created HBASE-9270:
-------------------------------------

             Summary: [0.94] FSTableDescriptors caching is racy
                 Key: HBASE-9270
                 URL: https://issues.apache.org/jira/browse/HBASE-9270
             Project: HBase
          Issue Type: Bug
    Affects Versions: 0.94.11
            Reporter: Andrew Purtell
            Priority: Minor


An occasionally failing test in 0.92 branch that concurrently executes master operations on a single table found this problem in FSTableDescriptors:

{code}
diff --git src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
index e882621..b0042cd 100644
--- src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
+++ src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java
@@ -221,8 +221,15 @@ public class FSTableDescriptors implements TableDescriptors {
     if (HConstants.HBASE_NON_USER_TABLE_DIRS.contains(htd.getNameAsString())) {
       throw new NotImplementedException();
     }
-    if (!this.fsreadonly) updateHTableDescriptor(this.fs, this.rootdir, htd);
-    long modtime = getTableInfoModtime(this.fs, this.rootdir, htd.getNameAsString());
+    if (fsreadonly) {
+      // Cannot cache here.
+      // We can't know if a modtime from the most recent file found in a
+      // directory listing at some arbitrary point in time still corresponds
+      // to the latest, nor that our htd is the latest.
+      return;
+    }
+    // Cache with the modtime of the descriptor we wrote
+    long modtime = updateHTableDescriptor(this.fs, this.rootdir, htd).getModificationTime();
     this.cache.put(htd.getNameAsString(), new TableDescriptorModtime(modtime, htd));
   }
{code}

After HBASE-7305 master operations are serialized by a write lock on the table.

However, 0.94 has code with the same issue:

{code}
  @Override
  public void add(HTableDescriptor htd) throws IOException {
    if (Bytes.equals(HConstants.ROOT_TABLE_NAME, htd.getName())) {
      throw new NotImplementedException();
    }
    if (Bytes.equals(HConstants.META_TABLE_NAME, htd.getName())) {
      throw new NotImplementedException();
    }
    if (HConstants.HBASE_NON_USER_TABLE_DIRS.contains(htd.getNameAsString())) {
      throw new NotImplementedException();
    }
    if (!this.fsreadonly) updateHTableDescriptor(this.fs, this.rootdir, htd);
    String tableName = htd.getNameAsString();
    long modtime = getTableInfoModtime(this.fs, this.rootdir, tableName);
    long dirmodtime = getTableDirModtime(this.fs, this.rootdir, tableName);
    this.cache.put(tableName, new TableDescriptorModtime(modtime, dirmodtime, htd));
  }
{code}

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