Tuesday, March 31, 2009

And: Action !!

It is 2009 already and I have finally some time again to keep programming.

Action handling
After much thought on how to implement the application behavior, currently all chat was sent around without validation and a MMO needs to have an application logic behind each channel, so specific action handling needed to be implemented to process each client info before sending it around in the channel. I have come to the conclusion, that probably the best way to do that is to implement them as a player (CC) module with an action handler (AH), both are stand alone processes, so whenever a group gets started up, it will automatically seek in a table for the AH of that group or else start up the generic entry as the handler. ANY message to be sent in a group gets sent to that single automated player entity, which then decides how to proceed, so for chat channels one can implement a word filter, NPC data can be implemented from here or zone channels will be able to send the movement data first to a physique server (far future) before sending that data to the clients. This single AH per channel will also keep track of connected clients, no matter what node they come from.

Some lessons learned of programming in Erlang:
First lesson: there are so many ways of implementing a certain behavior, it's mind boggling, one can choose from creating vanilla subroutines, a cherry mono- or multi-tasked applet, a table entry, a DB table or whole self managed entities, the choice is really vast and the problem is that you can be quite dynamic, so I have to sometimes go back and reread where all the magic comes from, all or most choices seem to be on par speedwise. Once decided, implementing it is a snap.
Second lesson: right size your multi-tasking; it's so tempting to create many, many processes, but syncronization can sometimes be a pain, so double check when to MT and when no to. Even when sync-ing is no problem, don't forget the possible size of the outcome, f.e. in the very beginning I sent each chat command as a separate task, but when I did the stress test with 50'000 generated users over 5 servers I found that 2.5 Billon concurrent tasks was a tad too much to handle for the framework, I wonder why that would be, how lame !!! =P
Third lesson: And Erlang programmers will hate me for this: OTP sucks big time, I found that it is much easier to write my own functionality, including but not limited to code upgrades in runtime across all connected servers, which requires a Doctor title in OTP to get to work, but only little effort to programm oneself, nowadays I only kick in some very few lines of code and voila, it upgrades !!
Forth lesson: they say love comes quickly and so does complexity !! Programs in Erlang are short and concise, but when implementing something new I find myself rewriting code in 5-6 programs in parallel, which isn't harder, but very different from "normal" programming languages.

Next to come is a channel authorization table that decides at logon (or later) what client should connect to which channel(s). I will also implement channel authorizations for that, which will be interesting =O, some must be system assigned (zones and instances), others with password, by group assignment (like a guild f.e.), open or user managed, so this will be an important feature and also some piece of work as I need to rewrite some code for that. Before or after that I will implement the first NPCs with some limited actions, oh and I still need to get the object table into the Apocalyx client to handle mutiple objects. But after these tasks I have the basic capabilities for an MMO, that is good news.

And Hello World !! Since my last update I seem to be getting quite a lof of hits on this blog I can even google this blog, much to my surprise actually and scary, too. SMASH is not ready for prime time after all and it may still be a while, due to the fact that I only do this on my spare time. So for the newcomer: feel free to read the MISSION STATEMENT. This is still vaporware, but whatever is mentioned herein is actually implemented, so one day (hopefully this year) the framework will be up and running and I will set up a closed alpha server for some testing. But I will not haste anything, quality overrules time requirements.

That's all for now !!



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