[zeromq-dev] zmq socket monitor goes wrong?

[Ondrej Kupka]

Hmm, but addr is a pointer, so I don't really that the ownership of the data. But I thought that https://github.com/tchap/gozmq-utils/blob/master/monitor.go#L188 copies the data… Will have to check to be sure…

On May 22, 2013, at 2:05 PM, Ondrej Kupka wrote:

> 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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