zloop gets confused if you create timer with same arg as expired timer

[hintjens]

Problem: if a timer expires (either by default, or by calling zloop_timer_end(), and you add a new timer with the same argument, zloop will destroy the new timer at the same time as it destroys the expired one.

Solution: when reaping zombie timers, only reap the first one. Secondly, add new timers to end of timer list, not start.

[hintjens]

Test case:

/*
This test exposes a problem with timer handling in zloop whereby
an attempt to replace an old timer with a new one in a socket
event handler does not succeed.

The test below initialises a timer which should be replaced (before
it expired) when the reactor calls s_socket_event.

However, what happens instead is that the new timer, though
added, never fires.

The problem does not occur if the original timer is not deleted,
in which case, both timers fire at the correct time.

Compile: gcc -o timer timer.c -I/usr/local/include -lczmq -lzmq

*/

#include "czmq.h"

static int
s_fire_timer (zloop_t *loop, zmq_pollitem_t *item, void *arg)
{
    printf ("Timer %p fired!\n", arg);
    return 0;
}

static int
s_socket_event (zloop_t *loop, zmq_pollitem_t *item, void *arg)
{
    zmsg_t *msg = zmsg_recv (item->socket);
    zmsg_destroy (&msg);
    printf ("Replacing timer with arg %p\n", item->socket);
    zloop_timer_end (loop, item->socket);

    // Adding a new timer with the same arg as the old one.
    // This will never fire!
    zloop_timer (loop, 1000, 1, s_fire_timer, item->socket);
    return 0;
}

int
zloop_test (bool verbose)
{
    int rc = 0;

    zctx_t *ctx = zctx_new ();
    assert (ctx);

    void *output = zsocket_new (ctx, ZMQ_PAIR);
    assert (output);
    rc = zsocket_bind (output, "inproc://timer.test");
    assert (rc == 0);
    void *input = zsocket_new (ctx, ZMQ_PAIR);
    assert (input);

    rc = zsocket_connect (input, "inproc://timer.test");
    assert (rc == 0);

    zloop_t *loop = zloop_new ();

    assert (loop);
    zloop_set_verbose (loop, verbose);

    //  Create a timer which we're going to *try* to replace
    // in the socket handler... (but it won't get replaced,
    // and will fire eventually!)
    printf ("Creating timer with arg %p\n", input);
    zloop_timer (loop, 5000, 1, s_fire_timer, input);

    zmq_pollitem_t poll_input = { input, 0, ZMQ_POLLIN };
    rc = zloop_poller (loop, &poll_input, s_socket_event, input);
    assert (rc == 0);

    // Send a message to trigger the handler:
    zstr_send (output, "Replace timer!");
    zloop_start (loop);
    zloop_destroy (&loop);
    assert (loop == NULL);

    zctx_destroy (&ctx);
    return 0;
}


int main( void )
{
    return zloop_test (true);
}

[ghost]

If this was fixed in 95381bf shouldn't this be closed?

[hintjens]

@shancat, welcome to the CZMQ maintainers' group :-) Feel welcome to merge pull requests, close issues, and invite others to the group. This is our process: http://rfc.zeromq.org/spec:22

[ghost]

Wow thanks! Just happy to help :) I'll be sure to read that document
again.