Kyle Cronan writes:
> Sinisa,
<cut>
>
> My process has three threads and three different MYSQL structures.
> I have found that if I don't let the three mysql_real_connect() calls go
> one by one when I spawn the daemon, and then wait in each thread for them
> all to finish, I get an error that my query was interrupted, or that I am
> attempting to run commands out of sync.
>
> This is the code I'm using to make the connections (I have this same code
> in three different source files for three different threads):
>
> pthread_mutex_lock(&num_connected_mutex);
> if(!db_connect(dbm)) {
> fprintf(stderr, "Error on db_connect(): %s\n",
> db_error(dbm));
> clean_die(1);
> }
> printf("main.cc: %d\n", num_connected+1);
> if (++num_connected==3)
> pthread_cond_broadcast(&all_connected_cond);
> else pthread_cond_wait(&all_connected_cond, &num_connected_mutex);
> pthread_mutex_unlock(&num_connected_mutex);
>
>
> I have also recently been running into errors with mysql_get_row returning
> errors (Commands out of sync; You can't run this command now), and when I
> insert the line:
>
> if (fork()) wait(NULL);
>
> just after the above code, the problem goes away. This leads me to
> believe that the problem is related to thread safety, but I'm not sure.
>
> Oh! It has just occured to me that one potential complication is that I
> have an unusual system of database wrappers. The calls above like
> db_connect, db_error, etc. are just wrappers for the mysql calls, except
> that I have a system of extensible database implementation modules, so the
> process itself is not actually linked to libmysqlclient_r, it dlopen()'s a
> shared library which is linked to the mysql client lib, and then defines
> the various database calls. Could this be causing my problems? Maybe I
> need to only load this module in one thread. Should it make any
> difference?
>
> Thanks for all your help.
>
> Kyle
>
> <[EMAIL PROTECTED]>
First of all, you should not over-complicated things. Even in our
server we do not call fork, as we have threads.
The error is possibly in your db_connect() wrapper. You must use each
time a different MYSQL * pointer for each mysql_real_connect and
separate query , result and row pointers too.
Regards,
Sinisa
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