ODBC Connector 5.1.6 hangs in a specific situation (recv)

[Bonny Gijzen]

Hi,


I have written a Delphi application which uses AdoQuery to talk to a database.
It first started with an Access database and later I migrated to MySQL using the ODBC connector 5.1.6

The problem I had was that the application holds the database connection open during the whole sessions (could be 5 hours), and sometimes the connection was dropped.

Now I manage to recover from this using the following:
1) Use the AUTORECONNECT flag when connecting to server
2) Set the wait_timeout to 28800 seconds after connection
3) Set the interactive_timeout to 28800 seconds after connection
4) Periodically send a simple query as some sort of keep-alive

Sometimes the connection is still dropped and I get a nice exception, which I catch and then I recreate the connection, so far so good.

Now very rarily when using a simple query my applications hangs.
The hang happens on recv() in function SQLExecDirectW() which is used by the connector.

Here is a stacktrace to show it:
77a1f85a +00e ntdll.dll NtWaitForSingleObject
76954861 +082 WS2_32.dll recv
6db6a64b +079 ODBC32.dll SQLExecDirectW
004cafa6 +056 BiljartScoreBord.exe ADODB TADOConnection.Execute
0058a8b8 +0b0 BiljartScoreBord.exe Unit2 TForm2.SendServerKeepAlive


For now I have no way to recover from this.
Is it normal that the connector could hang (for a long time) in some situation?

I am now trying to see if I can use the options READTIMEOUT and WRITETIMEOUT, but there is something confusing me:
The documentations says these options exist but only for server 5.1.12, but I would think this is an option for the client side (connector) so how is that related to the server??

Also it seems my provider is using MySql version 5.0.91 :(

Could this be something I am doing wrong?
(As I've said this happens only very rarily but it has happened a couple of times already. Also for now it happened only on Win 7 machines.)
Could this be a bug?

Does anyone have some insight on what to do now?
I am really stuck here and the application isn't useable if it will hang at some point it time.


Many thanks in advance for your answers and insights,

Bonny



Edited 1 time(s). Last edit at 09/24/2010 03:58AM by Bonny Gijzen.