Server architecture

From MountainfortWiki

== info == The server needs to be multithreaded to be capable of simulating catplosions and fluid dynamics. == world simulation step == * simulate world (terrain oriented jobs, ie. water, tree growth) ** threadpool (task stealing) that handles all jobs of this simulation step ** each job has read access to the complete world back buffer ** each job has exclusive read/write access to one chunk'S front buffer ** multiple jobs writing one chunk are queued in the same thread ** after all threads are finished the front buffer gets copied onto the back buffer ** each thread has messagebuffer, jobs the thread can write to the message buffer, *** after all threads are finished, *** the messages in the message buffer are written to the global message system ** fluid manager : (not every frame?) fluid simulation jobs are spawned by a manager for "awake" blocks (awake can be triggered by sim-job when water reaches edge : messagebuffer) ** light manager : not every frame, placing a torch triggers "awake"/recalc ** simulation has a fixed frames/second speed *** not all jobs need to calculate themselves every frame * jobs writing terrain must mark (messagebuffer) the terrain as changed for network messages to be generated * spin lock : busy-waiting for lock to avoid sleep, if maxfps long wait needed : sleep as job. * to avoid ram->cpucache bottleneck, attempt to process the same chunk-coordinates in the same thread (across multiple frames?) ** the simulation code of one chunk is implemented in lua == object simulation/think == there are 3 types of objects : mobiles(players,enemies,animals), items(stuff to pick up), buildings (workshops, bridges, doors..) * every worker thread has own lua state, and global single-threaded mode also. (objects may not have local state, all must be in property name-value list) * access via metatable. object orientation via dummy-object setting metatable according to object type (property) * complex structures and can be stored in properties via serialisation (ie json) * objects can have tags/groups * objects get messages with time-of-delivery (e.g. think again in 5 seconds, get poison damage, idle wandering animals) * every message triggers a job (jobs are written in lua) * priority (starttime) queue of messages * key-value lists for object properties, backbuffered, objects write themselves using message-buffer (update aka value-change) * fight/wound etc : send message to object (allows e.g. big blob spawns small blob) * inter object communication via message system * read only access to properties of every object * query objects in range (by type) (optionally flag that object always wants query sightrange in think step) * object manager creates and destroys objects, you need to send him which one you want to kill * pathfinding (one path-finding request isn't calculated in a parallel way, but multiple path-finding requests can be run at the same time (no-global-data structures, fully re-entrant?)) * ticker/timer to generate whatever timed messages (ie think message each 30 sec) == remaining super singlethreaded stuff == * complete singlethreaded part * handles network (send/recv/listen/accept) * handle complex things like falling trees (we can move this into the multihreading section if its to expesive) * worldsave/load == usecases == * drawbridge (changes terrain, managed as building) * fight between two mobiles * ai/decide-what-to-do : see and attack nearby enemy, cat-mating... * weather : rain produces small water ponds * player empties water bucket on area (awake fluid manager in this block) * lumberjack a tree (event based in single-threaded step) * cavein (check when solid tile is removed, if unconnected, apply gravity and deadly force) * closed-door-for-pathfinding, idea : change terrain (parameter) == later if neccessary, not needed for first prototype == * object jobs that can run multiple frames ? (complex ai, pathfinding etc... ) * world jobs that can access more than one chunk (treefall? area? cavein), in separate step after all the 1-chunk jobs are done ** needs to avoid concurrent write access to overlapping area == glossar == * world : terrain infos consisting of tiles in chunks == some notes == === jobs and their data access patterns === * gravity, rw on complete map * fluid, rw on complete map * vegetation, rw on complete map, slowakei * monster, r on complete map, rw on monster mobiles * pathfinding, r on complete map * lighting, r on complete map, w on lighting infos * weather, r on complete map, w on weather infos * collision/movement, r on complete map, w on mobiles === questions === * is it necessary to keep consistens snapshots of the data over multiple steps? * backbuffer or copied border? * data partitioned threading? === other similar implementations === * minecraft server todo * dust paper todo

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