maria-developers team mailing list archive

[Gonzalo Diethelm <gonzalo.diethelm@xxxxxxxxx>]

Hi Kristian, thanks for your reply.

This is what brew info says:

$ brew info mariadb-connector-c
mariadb-connector-c: stable 2.2.2 (bottled)
MariaDB database connector for C applications
https://downloads.mariadb.org/connector-c/


Notice that in the code snippet you sent, the comparison is greater than
*or equal to* zero; this could in fact add a zero timeout, right?

    if (vio_timeout >= 0)
    {
      b->timeout_value= vio_timeout;
      b->events_to_wait_for|= MYSQL_WAIT_TIMEOUT;
    }

By not passing MYSQL_WAIT_TIMEOUT back to the mysql_real_connect_cont()
call, the call returns right away, and I end up busy-polling it until the
connection is complete. That's what I meant by polling; I was just
mentioning that I tried that, of course that would not be a long-term
solution.

I tried adding the CONNECT_TIMEOUT option, and now the timeout for
the mysql_real_connect_start() call does come back as 10_000 ms, but the
timeout for the mysql_real_connect_cont() still keeps coming as zero.

Cheers,
Gonzo


On Fri, Sep 23, 2016 at 4:21 PM, Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx>
wrote:

> Gonzalo Diethelm <gonzalo.diethelm@xxxxxxxxx> writes:
>
> > In my code, I am calling mysql_real_connect_start(), and the return value
> > indicates that MySQL is waiting for READ and TIMEOUT. However, if I call
> > mysql_get_timeout_value() (or the _ms() version) right after that, it
> > returns 0. Is this expected? As far as I can see, this is causing the
> next
>
> No, it is not expected. MYSQL_WAIT_TIMEOUT should only be returned in
> status
> if a non-zero MYSQL_OPT_CONNECT_TIMEOUT is set with mysql_options().
>
> > This is on OS X 10.11.6 with the MariaDB client just installed via brew;
> > mariadb_config --version says 5.5.1.
>
> Hm. Can you clarify exactly which version of the library you are using? Are
> you using the library that is bundled with the server (seems likely since
> you are using the async_queries.c example from the server source tree)? Or
> are you using the separate connector-c library?
>
> Version 5.5.1 of the server did not include the non-blocking library...
>
> > This is the code I'm calling:
> >
> >             status = mysql_real_connect_start(&ret, &mysql, h, u, p, d,
> 0,
> > 0, 0);
> >             printf("MYSQL connect %d", status);
> >             if (status & MYSQL_WAIT_TIMEOUT) {
> >                 unsigned int ms = mysql_get_timeout_value_ms(&mysql);
> >                 printf(" and includes a timeout of %u ms", ms);
> >             }
> >             printf("\n");
>
> I tried adding this to async_queries.c, but I could not reproduce. I get
>
>   MYSQL connect 2
>
> If I add to the source
>
>     unsigned int my_timeout = 10;
>     mysql_options(&sds[i].mysql, MYSQL_OPT_CONNECT_TIMEOUT, &my_timeout);
>
> I get:
>
>   MYSQL connect 10 and includes a timeout of 10000 ms
>
> Can you try to apply the attached patch to async_queries.c and see if you
> can reproduce the problem with that code? If so, maybe it is something
> specific to OS X? If not, then maybe something goes wrong in your code?
>
> > That code prints: MYSQL connect 9 and includes a timeout of 0 ms
>
> The thing is, the only places in the code that set MYSQL_WAIT_TIMEOUT()
> look
> like this:
>
>     if (vio_timeout >= 0)
>     {
>       b->timeout_value= vio_timeout;
>       b->events_to_wait_for|= MYSQL_WAIT_TIMEOUT;
>     }
>
> And mysql_get_timeout_value_ms() basically returns b->timeout_value. So it
> is surprising to see your code getting MYSQL_WAIT_TIMEOUT with a zero value
> for timeout...
>
> > I did find two ways to make the code work:
> >
> >    1. Not passing MYSQL_WAIT_TIMEOUT back to the
> mysql_real_connect_cont()
> >    (so it thinks a timeout has not happened at all). This allows all the
> >    queries to actually complete, but the code ends up polling heavily.
>
> Not passing MYSQL_WAIT_TIMEOUT back should not cause any polling (though it
> will disable the timeout functionality). But nor should it be necessary to
> special case this, obviously.
>
> Hope this helps,
>
>  - Kristian.
>
>
> diff --git a/tests/async_queries.c b/tests/async_queries.c
> index 76e884e..486458c 100644
> --- a/tests/async_queries.c
> +++ b/tests/async_queries.c
> @@ -168,6 +168,12 @@ state_machine_handler(int fd __attribute__((unused)),
> short event, void *arg)
>    case 0:
>      /* Initial state, start making the connection. */
>      status= mysql_real_connect_start(&sd->ret, &sd->mysql, opt_host,
> opt_user, opt_password, opt_db, opt_port, opt_socket, 0);
> +    printf("MYSQL connect %d", status);
> +    if (status & MYSQL_WAIT_TIMEOUT) {
> +      unsigned int ms = mysql_get_timeout_value_ms(&sd->mysql);
> +      printf(" and includes a timeout of %u ms", ms);
> +    }
> +    printf("\n");
>      if (status)
>        /* Wait for connect to complete. */
>        next_event(1, status, sd);
> @@ -410,9 +416,11 @@ main(int argc, char *argv[])
>    num_active_connections= 0;
>    for (i= 0; i < opt_connections; i++)
>    {
> +    unsigned int my_timeout = 10;
>      mysql_init(&sds[i].mysql);
>      mysql_options(&sds[i].mysql, MYSQL_OPT_NONBLOCK, 0);
>      mysql_options(&sds[i].mysql, MYSQL_READ_DEFAULT_GROUP,
> "async_queries");
> +    mysql_options(&sds[i].mysql, MYSQL_OPT_CONNECT_TIMEOUT, &my_timeout);
>
>      /*
>        We put the initial connect call in the first state 0 of the state
> machine
>
>


-- 
Gonzalo Diethelm
gonzalo.diethelm@xxxxxxxxx