[Twisted-Python] Advice Request: Under what circumstances should I use AMP's Command Response field?

[Laurens Van Houtven]

Hi Burak,

On Tue, Aug 20, 2013 at 12:21 PM, Burak Nehbit <burak at nehbit.net> wrote:

> Hi there,
>
> I was meaning to ask you all about the 'proper' way to use AMP in regards
> to two–way communication. The problem I am facing is quite simple, I am
> building a simple peer–to–peer network in which the user:
>
> a) When sent a handshake, returns a handshake,
> b) When asked for fingerprints of posts in the local, returns it, and then
> asks for the same thing,
> and finally, c) If any of the fingerprints do not match posts, request
> those posts with the fingerprint.
>
> The only non–symmetric step I have in my protocol is the last one.
>
> My question is, should I send my responses over the same AMP command as a
> response to the command requested, or should I just return an ACK (a
> boolean value of true, to confirm receipt) and then initiate a separate AMP
> request from local to the same remote?
>

Keep in mind that AMP commands are always ack'ed without you needing to
specify any kind of value, unless you set requiresResponse = False on the
Command class.

That would mean I would need to handle my open–connections pool by myself,
> to prevent posts from a non–initiated machine being accepted into the local
> machine, but I do need to implement that anyway due to the complexity of my
> business rules.


I don't understand this part. It sounds like an authentication problem, no?


> At that point, it seems that I am (Am I?) just using AMP as a remote
> method header I don't strictly need, and I could just use LineReceiver—all
> my data is text—to do my bidding.
>

It's usually correct that you can do things with LineReceiver, but it's
also usually true that AMP is doing stuff for you ;)

Some more information about your system would be useful. Are posts
append-only? Would it make sense to have a given serialization of them? If
so, a hash chain would allow you to sync with just one hash value. A
consensus protocol might help you figure out what that serialization is.

cheers
lvh
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