Re: [Monotone-devel] mtn automate tcp

[Ulf Ochsenfahrt]

Lapo Luchini wrote:
> I was thinking... wouldn't a "automate tcp" be useful?
>
> I mean something that just accepts TCP connections and then talks the
> "automate stdio" protocol: having an always-on server listening on
> 127.0.0.1:something could be very nice e.g. from PHP access, when it
> would be difficult to maintain an open "automate stdio" available from
> all workers.
>
> Or there is some problem against that I cannot see right now?
>
>     Lapo
>
> PS: this could be easily done using "tcpserver" but that would accept
> only one connection at a time, for file-locking problems, isn't that so?

Hi!

This approach has multiple problems (and probably more I'm not aware of 
right now):

1. Security
Anyone who can connect is allowed unlimited access to your db. Even if 
you only allow connections from localhost, you can run into problems on 
multi-user systems. You could, however, add an authentication layer 
before you actually allow operations.

2. Error Handling
Right now, automate stdio handles errors by exiting the mtn instance. So 
you'd need to be able to start a new 'server' from your 
php/java/c/whatever anyway.

3. Working Directory
automate doesn't allow you to change the working directory. So you 
couldn't use it to handle workspaces (or only at most one).

4. Limited Operations
automate stdio doesn't support such basic operations as add, drop, 
rename, or commit.

5. Multiple Access
You'd need to figure out some way to handle the locking issues you get 
with multiple concurrent access.


Now, in my opinion it isn't such a bad idea. I'm favoring a solution 
where mtn automate stdio works like a monotone shell, where you can 
issue all kinds of monotone commands. Error situations would result in 
error results (automate stdio provides for reporting error codes, but 
this is often not used and instead, the mtn instance is simply exited - 
imho this severly limits the usability of automate stdio). This approach 
could solve 2, 3, and 4.

Cheers,

-- Ulf

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