[jira] [Created] (HIVE-14524) BaseSemanticAnalyzer may leak HMS connection

["Chao Sun (JIRA)" <ji...@apache.org>]

Chao Sun created HIVE-14524:
-------------------------------

             Summary: BaseSemanticAnalyzer may leak HMS connection
                 Key: HIVE-14524
                 URL: https://issues.apache.org/jira/browse/HIVE-14524
             Project: Hive
          Issue Type: Bug
          Components: HiveServer2
    Affects Versions: 2.2.0
            Reporter: Chao Sun
            Assignee: Chao Sun


Currently {{BaseSemanticAnalyzer}} keeps a copy of thread-local {{Hive}} object to connect to HMS. However, in some cases Hive may overwrite the existing {{Hive}} object:

{{Hive#getInternal}}:
{code}
  private static Hive getInternal(HiveConf c, boolean needsRefresh, boolean isFastCheck,
      boolean doRegisterAllFns) throws HiveException {
    Hive db = hiveDB.get();
    if (db == null || !db.isCurrentUserOwner() || needsRefresh
        || (c != null && db.metaStoreClient != null && !isCompatible(db, c, isFastCheck))) {
      return create(c, false, db, doRegisterAllFns);
    }
    if (c != null) {
      db.conf = c;
    }
    return db;
  }
{code}

*This poses an potential problem*: if one first instantiates a {{BaseSemanticAnalyzer}} object with the current {{Hive}} object (let's call it A), and for some reason A is overwritten by B with the code above, then {{BaseSemanticAnalyzer}} may keep using A to contact HMS, which will leak connections.

This can be reproduced by the following steps:
1. open a session
2. execute some simple query such as {{desc formatted src}}
3. change a metastore property (I know, this is not a perfect example...), for instance: {{set hive.txn.timeout=500}}
4. run another command such as {{desc formatted src}} again

Notice that in step 4), since a metavar is changed the {{isCompatible}} will return false, and hence a new {{Hive}} object is created. As result, you'll observe in the HS2 log that an connection has been leaked.




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