[zeromq-dev] zmq socket monitor goes wrong?

[Ondrej Kupka]

Hi Lourens,

Thanks for the reply.

I am not sure that this is the problem. It works in the following way:

    1. Receive frames in Go by calling gozmq.Socket.RecvMultipart(). This already copies the data (Go takes the ownership).
    2. Pass it to the C function parse_socket_event(), which is "generated" at compile time to work with either zeromq3-x events protocol (single frame containing a struct) or libzmq events protocol (2 frames). Fill in malloc'd gzu_socket_event_t, which is the same for both protocols.
    3. Pass the gzu_socket_event_t pointer back to Go and use it further. Then free it by calling free from Go.

Now the bottom line is that the event struct is just a frame of data received before and is thus in my (Go) ownership and is garbage-collected by Go later, so this can't be the issue.

But it is possible that I am mistaken :-)

Thanks again,
Ondra

On May 22, 2013, at 1:22 PM, Lourens Naudé wrote:

> Hi Ondra,
> 
> Afaik you'd need to memcpy the data - from the event struct as it can be free'd from within libzmq in nondeterministic fashion and thus https://github.com/tchap/gozmq-utils/blob/master/parse_socket_event.c#L51-L52 won't work. See the test cases in libzmq for an example :
> 
> https://github.com/zeromq/libzmq/blob/master/tests/test_monitor.cpp#L55
> 
> On Wed, May 22, 2013 at 11:50 AM, Ondrej Kupka <ondra.cap at gmail.com> wrote:
> Hi,
> 
> I am working on zmq_socket_monitor bindings + some abstractions for Go. I am almost there, but I am getting very weird results when I run my tests (one large test for now to be honest). You can see the output at http://pastebin.com/kqgjLFyt. As you can see, only once out of ten runs of the tests, event addr is filled in properly.
> 
> I am not sure what is happening, but I am pretty sure that I am getting this from libzmq (gozmq) and I am not breaking it anywhere in my Go. In any case, you can check sources at https://github.com/tchap/gozmq-utils, the C part is at https://github.com/tchap/gozmq-utils/blob/master/parse_socket_event.c
> 
> If you find any silly mistake of mine, please let me know, otherwise it is probably a libzmq bug…
> 
> Thanks in advance,
> Ondra Kupka
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