[Monotone-devel] Re: [Monotone-commits-nodiffs] Revision 63a44f0a3ebbed02b4426db2edd700c5a7b03a2f

[Thomas Moschny]

You wrote:
> Thomas, can you elaborate on the state of this http/json webservice you
> are refering to here:
>
> address@hidden wrote:
> > First version of the plugin using the http/json webservice instead of
> > spawning a mtn automate process itself. Some things still have to be
> > fixed though.
>
> It sounds very interesting, but I don't currently understand how is it
> related to the trac plugin. 

It's simply that I realized that forking off and talking to a monotone 
subprocess from within the trac plugin is not the best thing to do, for 
several reasons:

- Depending on how trac is deployed (e.g. if mod_python is used), it might 
happen that we create multiple mtn subprocesses, which will put unnecessary 
(memory) stress on the server and increase the chances for locking issues.

- Monotone used via automate stdio currently outputs some of its error 
messages on stderr. But properly receiving everything from stdout *and* 
stderr, without blocking on stderr, is not easy (read: a big mess) to do in a 
portable way. You need either a non-blocking read(), or create your own 
eventloop, or use threads, or whatever.

This is when I decided to look at twisted, which promises to exactly do that. 
But even using twisted, things work best if done in a stand-alone application 
and not in a plugin somehow executed by the webserver. That's why I created 
that daemon. As I currently only use it from the plugin, it lives in the same 
branch.

> It's based on twisted, right?

Yes, it is.

Currently, it is read-only and tries to use a simple url schema. Information 
is fetched from an mtn subprocess via automate stdio, parsed and then sent to 
the client as json encoded data.

> Can I run a standalone http/json service?  

Yeah, sure. There is some usage information at the top of 
twisted/plugins/mserv.py. Feel free to test it and send me comments or 
suggestions about it.

Regards,
Thomas