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From karanmehta93 <...@git.apache.org>
Subject [GitHub] phoenix pull request #277: PHOENIX-3757 System mutex table not being created...
Date Wed, 25 Oct 2017 20:17:19 GMT
Github user karanmehta93 commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/277#discussion_r146974246
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java
---
    @@ -2526,8 +2541,14 @@ private void createOtherSystemTables(PhoenixConnection metaConnection)
throws SQ
             try {
                 metaConnection.createStatement().execute(QueryConstants.CREATE_FUNCTION_METADATA);
             } catch (TableAlreadyExistsException ignore) {}
    +        // We catch TableExistsException in createSysMutexTable() and ignore it. Hence
we will also ignore IOException here.
    +        // SYSTEM.MUTEX table should not be exposed to user. Hence it is directly created
and used via HBase API.
    +        // Using 'CREATE TABLE' statement will add entries to SYSTEM.CATALOG table, which
should not happen.
    +        try {
    +            createSysMutexTable(hBaseAdmin, ConnectionQueryServicesImpl.this.getProps());
    +        } catch (IOException ignore) {}
    --- End diff --
    
    Yes, this is a serious case that we should discuss. The correct thing to do is to probably
FAIL the connection itself or possibly have a retry logic for creating the table. 
    
    This is because in the `acquireUpgradeMutex()` method we check if either SYSMUTEX exists
or SYS:MUTEX table exists. The only possible case where both of those tables can be missing
is when a client is trying to migrate the table, which disables the old table and creates
the new one. There is a brief period of time when none of these table exists. Hence we throw
`UpgradeInProgressException` exception in such a case.
    
    We have no way to determine if the table doesn't exist at well v/s the point that the
table is in migration.
    Is there any other scenario in which this can affect?


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