ODBC questions

Michael McDaniel <>
Sat Feb 11 20:13:53 CET 2006


 On Sun, Feb 05, 2006 at 04:39:12PM +0100, Mickael Remond wrote:
 > Hello,
 > 
 > I have recently been working a lot with ODBC and Erlang. One problem /
 > question remains: Is there any mechanism to detect when the connection
 > to the database is lost ? The purpose is to be able to try restarting
 > the connection. 
 > I looked at the ODBC code, but did not find any relevant parts.
 > For now, the behaviour seems to be the following: When querying a
 > database who went offline, I get an error as the query response. The
 > text of the error explains that the database is not more reachable but
 > the ODBC process is still there.
 > 
 > I suspect that such reconnection mechanism should be handled by the ODBC
 > driver. I have been doing my tests with MySQL. 
 > 
 > Does someone here have experienced the same reconnection problem with
 > ODBC ? 
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 I (perhaps naively) do the following in a (reliable) production system:
 
 
 readUpdateQuarry(Ref, CacheCallid, NewCallid) ->
 
 Z = "insert into quarry select "  etc. etc. proprietary stuff
 
   case odbc:sql_query(Ref, Z) of
     {updated, Return} -> {updated, Return} ;
     {_, Error}        -> expmaster:log_error(?MODULE, ?LINE,
 				 'odbc:sql_query', Error) ,
 		         {error, Error}
   end
 .
 
 
 where Ref is an ODBC connection.  Everything works fast enough for
 this system for the calling function to disconnect/reconnect if
 there is a problem.
 
 Other insert/query functions I have will create a new connection
 and destroy the connection for each call.  This is fast enough
 in my production environment also.  I originally had designed
 to have a process that marshalled ODBC connections for the workers.
 That proved to be more hassle than it was worth since the above
 simpler system works plenty fast enough. 
 
 
 ~Michael
 
 
 > 
 > -- 
 > Mickaël Rémond
 >  http://www.process-one.net/
 
 -- 
 Michael McDaniel
 Portland, Oregon, USA
 http://autosys.us
 +1 503 283 5284



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