[mythtv] mythbackend 0.22-fixes problem with duplicate database connection name

[Roger James]

On 02/03/2010 18:34, Jim Stichnoth wrote:
> On Tue, Mar 2, 2010 at 10:17 AM, Roger James
> <roger at beardandsandals.co.uk>  wrote:
>    
>> I have been recently seeing a problem with mythbackend (0.22-fixes rev
>> 23482) reporting that the database connection had gone away and some (all?)
>> database transactions being rejected with a "Driver not loaded" error. The
>> common factor behind these failures seems be that they all start after the
>> following QSqlDatabasePrivate messages are logged.
>>
>> QSqlDatabasePrivate::removeDatabase: connection 'DBManager5' is still in
>> use, all queries will cease to work.
>> QSqlDatabasePrivate::addDatabase: duplicate connection name 'DBManager5',
>> old connection removed.
>> 2010-02-28 05:32:54.876 New DB connection, total: 6
>> 2010-02-28 05:32:54.877 Connected to database 'mythconverg' at host: myth
>> 2010-02-28 05:32:54.878 MSqlDatabase::OpenDatabase(), db object is not
>> valid!
>> QSqlQuery::exec: database not open
>> QSqlQuery::exec: database not open
>> 2010-02-28 05:32:54.933 Driver error was [1/-1]:
>> Driver not loaded
>> Database error was:
>> Driver not loaded
>>
>> This leaves the backend in a confused state where it appears that some
>> database transactions are failing are and I suspect some are still working.
>> Subsquent new recordings appear in the new recordings list but but have no
>> file associated with them. My guess is that database connections
>> "DBManager0" to "DBManager4" are still working but the old "DBManager5" is
>> now broken.
>>
>> I do not recollect having this problem on my old single processor backend
>> system. I think I have only seen it on my new quad core fast processor
>> system. But I cannot be certain.
>>
>> The problem usually seems to occur when the system is just idling doing EIT
>> scans. But I have it occur twice when three recordings tried to start at the
>> same time.
>>
>> The only similar problem I can find is
>> http://svn.mythtv.org/trac/ticket/7836. But this is reported as a frontend
>> problem. I wonder if the same bug in MDBManager could be causing my problem.
>>      
> I suspect this is due to the existing bug I mentioned in the first
> comment of #7836, where a field in MDBManager is being used both to
> keep track of the number of open DB connections and to create unique
> connection names, allowing the possibility of duplicate connection
> names and the log messages you posted.  This can happen in any myth
> app, not just the frontend.
>
> Jim
>    
I think I will just apply your split of m_connID to my 0.22-fixes source 
leaving out the rest of your patch and see what happens. It looks pretty 
benign.

Roger