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From Paul Davis <>
Subject Re: Replacing the _external API
Date Fri, 24 Sep 2010 18:30:53 GMT
On Fri, Sep 24, 2010 at 2:19 PM, Robert Newson <> wrote:
> Assuming it's straightforward to extend OTP-style process monitoring
> to external processes (and I'm assuming that the couchjs processes are
> so monitored today) then I like the proposal to add both of these
> things.

Yeah, intend for the process monitoring to behave almost exactly like
it does current for _external scripts. Just a "restart when dies" sort
of configuration. The config protocol over stdio was a last minute
idea to make it easy for implementors to figure out where their couch
is and what not.

> My obvious motivation is couchdb-lucene so, with that hat on, would
> this mechanism obviate the need for start couchdb-lucene externally
> and make the Python hook script obsolete? I think it does. Finally,
> there are cases where c-l users might wish to locate their c-l server
> on a different box, so we should allow the proxying independently of
> the launch-on-demand-and-keep-me-running bit.
> B.

They'll be completely separate features for precisely this sort of
reason. I haven't quite figured out the details on proxies to external
hosts. I see the real need, but I feel as though we should have a
method for disabling the external host ability as well.

> On Fri, Sep 24, 2010 at 7:10 PM, Paul Davis <> wrote:
>> At CouchCamp there was a bit of discussion on replacing the _external
>> API with something a bit more modern to give _external processes more
>> control over their environment.
>> The idea was born out of a discussion with Robert Newson who mentioned
>> that couchdb-lucene really only needs a reverse proxy to put itself in
>> the same URL namespace. It occurred to us that having a reverse proxy
>> instead of the current _external stdio protocol would allow lots of
>> other interesting features like node.js integration, as well as allow
>> implementors to handle requests in parallel and so on and such forth.
>> The major drawback that was identified was that if we switched to just
>> a reverse proxy, people would then be responsible for handling the
>> process management of their _external handlers. Ie, they'd have to
>> configure daemon monitoring to make sure the processes stayed up and
>> what not. The solution we came up with was to include another feature
>> that did process management. Ie, something that would bring up an OS
>> process when the server booted, and respawn it if it crashed. There'd
>> be no connection to the _externals. Other than the basic "just keep a
>> process up" sort of behaviour, the only other thing I could see adding
>> is a simple stdio protocol to get configuration values from CouchDB.
>> Other people have expressed interest in just the process management
>> functionality as well which makes me think that having the two new
>> features to replace the _external API would be both easier on
>> developers as well as providing more functionality.
>> So now I'm looking for feedback on what other people might think of
>> this. I'll start working on this fairly soon if I don't hear any major
>> objections.
>> HTH,
>> Paul Davis

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