[erlang-questions] gen_event streamer

Marcel Meyer <>
Wed Dec 15 13:17:40 CET 2010


Hi Barry,

It should be able to run on Windows and Linux and the maximum resolution
should be 1 sec.
I have a prototype (non OTP) version that polls the directory with
file:list_dir(Dir). It should also be mentioned that for the most part, the
directory being watch will also be emptied as events get processed, so I
shouldn't run into an issue where there might be millions of files in a
folder which will slow down the polling.

What do you think?

Regards,
Marcel

On Tue, Dec 14, 2010 at 6:50 PM, Barry Nicholson <>wrote:

> Marcel:
>
> Some further information would be helpful.  Are you going to be doing
> this on unix/linux/windows?  What OS?   There are different mechanisms
> available for the different OSes.   It might change the design.
>
> Also, what's the timing requirements?   Do you want to know when the
> files get added immediately or can you wait a few seconds, a few
> minutes, or a few hours.   This could also change the design.
>
> Barry Nicholson
>
>
> On 12/14/10 5:36 PM, Marcel Meyer wrote:
> > Hi there,
> >
> > I would like to request your guidance in the following scenario where I
> want
> > to follow OTP conventions:
> > I want to mount a process on a directory that fires an event when files
> get
> > added or deleted.  I thought the API should look like this:
> >
> > fs_watcher:add_handler("/User/marcel/downloads/", pid).
> > fs_watcher:add_handler("/User/john/downloads/", pid).
> >
> > Now I'm thinking that there should be 1 supervisor that keeps a process
> for
> > each folder alive and sends a message to pid every time something happens
> in
> > that folder, so in my example above, there would be 2 processes being
> kept
> > alive.
> >
> > Am I talking about the server/streamer part of the gen_event?
> > Or do I need to roll my own by stitching an app/sup together that manage
> the
> > spawned directory processes?
> >
> > Regards,
> > Marcel
> >
>
>
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