[erlang-questions] gproc:monitor(Key, follow)

[Camille Troillard]

On 29 May 2014, at 15:32, Ulf Wiger <ulf@REDACTED> wrote:

> Have you looked at gproc_monitor:subscribe/1. Supposedly it does what you want.

Ahhh, beautiful this is exactly what I need.
Read the fine documentation they say...

Thanks Ulf.

Cam




> On 29 May 2014, at 14:09, Camille Troillard <lists@REDACTED> wrote:
> 
>> Hello Ulf,
>> 
>> 
>> On 29 May 2014, at 10:33, Ulf Wiger <ulf@REDACTED> wrote:
>> 
>>> In this sense, gproc:monitor/2 works like erlang:monitor/2, which also stays silent if the object is alive and well.
>> 
>> That makes sense.
>> 
>> 
>>> Perhaps the easiest thing to do is to simply look up the name right after calling monitor()?
>> 
>> Yes I could do that, though I wished I only had a single place where I act on the registration notifications.
>> 
>> So I could use nb_wait, but there is a small discrepancy where its callback signature {gproc, Ref, registered, {Key, Pid, Value}} is not the same as the one of monitor {gproc, registered, Ref, Key}. Maybe there was a good reason for this, unfortunately this prevents me from having a unified notification of a process coming up.
>> 
>> 
>> Thank you.
>> Cam
>> 
>> 
>>> 2014-05-28 18:04 GMT+02:00 Camille Troillard <lists@REDACTED>:
>>> OK, so it seems gproc:monitor(Key, follow) works, however if the name is already registered the message {gproc, registered, Ref, Key} is not sent. I would have expected the message to be sent since {gproc, unreg, Ref, Key} is sent when the name is not registered. Is this a bug?
>>> 
>>> 
>>> On 28 May 2014, at 17:15, Camille Troillard <lists@REDACTED> wrote:
>>> 
>>> > Hello,
>>> >
>>> > I would like to take action when a name gets registered under gproc.
>>> >
>>> > I understood I could call gproc:monitor(Key, follow) during initialization but my process does not get notified of the name availability. Therefore I had to replace that call to gproc:nb_wait, and then monitor the process in the callback handler. I wish I could follow the former approach.
>>> >
>>> > Can someone explain the usage pattern of gproc:monitor(_, follow)?
>>> > I am trying to understand why this would not work.
>>> > Thanks!
>>> >
>>> > Camille
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