Monday, April 28, 2008

Some more remote utilities

Some might know that SMASH has included into its belly an automatic updating system, which allows to compile all modules and reload them on all connected nodes in run time, without ever shutting the system down. On occasions this fails and a certain service shuts down. To get a hang on this, we have created some utility routines, one permits to execute commands remotely (on the other nodes) and the other shows if any module is executing old code, so very soon we will be able to first check what module on which node is executing old code before a new compile is allowed. So far the problem seems only to reside on longer lasting timers, which are not included in the update signal, all others update correctly (it seems). Also with these utility routines we could now easily start all preconfigured services (in the cluster file) remotely, without needing to touch then anymore. Some other fixes are that the CC proxy can now send tells or whispers without subscribing to any channel; KVS can now cache and forget, when you ask kvs:cache(M,F,A,Timer) it now will update every "Timer" ms and forget about the value after a minute, so the dictionary does not pile up with hundreds of unused values, this works like a garbage collection to keep KVS trim and slim. And more tests on Mnesia have been executed and curious enough on remote nodes the dirty function is slower than the normal database access with transactions and as to be expected KVS suffers from the initial Mnesia access, but afterwards blazes thru repeated accesses, so no matter how much we try to optimize the database access, the cached behind KVS approach is still the best when repeated access to data is required. Dedicated MMO literature also comes to the conclusion that processes on a multi server structure should update their data every 5 sec., less seems to be too much. And the cloud infrastucture has given some new ideas, Erlang already has the ability to spawn remote processes, so I guess, we just might implement our own flavour of it, by speed measuring each connected node and on the other hand check how many processes are already running there, this could be something like a routine task that executes per "X" interval and then when asked to spawn a process it checks for the best node to do so, a kind of "cloud_spawn(M,F,A)". This would make the SMASH ready to process any kind of task actually, not just a specialized Simulation Framework. It just might happen =) .

And Apocalyx can indeed use tables to store toon data, I played around with the Urban Tactics demo and it can easily handle some 200 toons running around there, very nice, now we need this networked. ;)



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