Created
April 18, 2017 04:09
-
-
Save eglyph/413ba6bbf1e729ba4fc402318cf05163 to your computer and use it in GitHub Desktop.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| -module(frequency). | |
| -export([start/0,allocate/0,deallocate/1,stop/0]). | |
| -export([init/0]). | |
| -compile(export_all). | |
| %% Usage: | |
| %% SupervisorPid = spawn(frequency, super, []). | |
| %% frequency:run_clients(7, frequency). | |
| %% ... see clients working ... | |
| %% ... using observer:start() find and kill frequency:loop() | |
| %% ... see server restarted, clients working... | |
| %% a simple supervisor that restarts a died server | |
| super() -> | |
| process_flag(trap_exit, true), | |
| ServerPid = spawn_link(frequency, init, []), | |
| register(frequency, ServerPid), | |
| io:format("Started supervisor, server pid is ~p~n", [ServerPid]), | |
| receive | |
| {'EXIT', ServerPid, Why} -> | |
| io:format("A server has terminated, reason: '~p', restarting~n", | |
| [Why]), | |
| super() | |
| end. | |
| start() -> | |
| ServerPid = spawn(frequency, init, []), | |
| register(frequency, ServerPid), | |
| ServerPid. | |
| init() -> | |
| process_flag(trap_exit, true), %%% ADDED | |
| Frequencies = {get_frequencies(), []}, | |
| loop(Frequencies). | |
| % Hard Coded | |
| get_frequencies() -> [10,11,12,13,14,15,16,17,18,19]. | |
| %% The Main Loop | |
| loop(Frequencies) -> | |
| receive | |
| {request, Pid, allocate} -> | |
| {NewFrequencies, Reply} = allocate(Frequencies, Pid), | |
| Pid ! {reply, Reply}, | |
| loop(NewFrequencies); | |
| {request, Pid , {deallocate, Freq}} -> | |
| NewFrequencies = deallocate(Frequencies, Freq), | |
| Pid ! {reply, ok}, | |
| loop(NewFrequencies); | |
| {request, Pid, stop} -> | |
| Pid ! {reply, stopped}; | |
| {'EXIT', Pid, _Reason} -> %%% CLAUSE ADDED | |
| NewFrequencies = exited(Frequencies, Pid), | |
| loop(NewFrequencies) | |
| end. | |
| %% Functional interface | |
| allocate() -> | |
| frequency ! {request, self(), allocate}, | |
| receive | |
| {reply, Reply} -> Reply | |
| end. | |
| deallocate(Freq) -> | |
| frequency ! {request, self(), {deallocate, Freq}}, | |
| receive | |
| {reply, Reply} -> Reply | |
| end. | |
| stop() -> | |
| frequency ! {request, self(), stop}, | |
| receive | |
| {reply, Reply} -> Reply | |
| end. | |
| %% The Internal Help Functions used to allocate and | |
| %% deallocate frequencies. | |
| allocate({[], Allocated}, _Pid) -> | |
| {{[], Allocated}, {error, no_frequency}}; | |
| allocate({[Freq|Free], Allocated}, Pid) -> | |
| link(Pid), %%% ADDED | |
| {{Free, [{Freq, Pid}|Allocated]}, {ok, Freq}}. | |
| deallocate({Free, Allocated}, Freq) -> | |
| {value,{Freq,Pid}} = lists:keysearch(Freq,1,Allocated), %%% ADDED | |
| unlink(Pid), %%% ADDED | |
| NewAllocated=lists:keydelete(Freq, 1, Allocated), | |
| {[Freq|Free], NewAllocated}. | |
| exited({Free, Allocated}, Pid) -> %%% FUNCTION ADDED | |
| case lists:keysearch(Pid,2,Allocated) of | |
| {value,{Freq,Pid}} -> | |
| NewAllocated = lists:keydelete(Freq,1,Allocated), | |
| {[Freq|Free],NewAllocated}; | |
| false -> | |
| {Free,Allocated} | |
| end. | |
| %% -------------------------------------------------- | |
| %% Client functionality | |
| % flush a mailbox | |
| clear() -> receive | |
| _Msg -> clear() | |
| after 0 -> ok | |
| end. | |
| %% a generic function that sends a message somewhere and expects an answer | |
| %% timeout param is added for easier testing | |
| call(Who, Message, Timeout) -> | |
| process_flag(trap_exit, true), | |
| TargetPid = whereis(Who), | |
| link(TargetPid), % allows passing a registered name | |
| Who ! Message, | |
| receive | |
| {'EXIT', _Pid, _Why} -> {error, server_died}; | |
| {reply, Reply} -> unlink(TargetPid), | |
| Reply | |
| after Timeout -> {error, timeout} | |
| end. | |
| alloc(ServerPid) -> call(ServerPid, {request, self(), allocate}, 1000). | |
| free(ServerPid, Freq) -> | |
| call(ServerPid, {request, self(), {deallocate, Freq}}, 1000). | |
| %% a client process emulator | |
| client(ClientNum, ServerPid) -> | |
| Timeout = 5000 + rand:uniform(2000), | |
| Reply = alloc(ServerPid), | |
| case Reply of | |
| {ok, Freq} -> | |
| io:format("Client #~p allocated ~p~n", [ClientNum, Freq]), | |
| Res = free(ServerPid, Freq), | |
| io:format("Client #~p deallocated frequency, result is ~p~n", | |
| [ClientNum, Res]), | |
| timer:sleep(Timeout), | |
| client(ClientNum, ServerPid); | |
| {error, Why} -> | |
| io:format("Client #~p received an error ~p, exiting~n", | |
| [ClientNum, Why]), | |
| exit | |
| end. | |
| %% spwans a given number of clients simulator | |
| %% Server is a registered name | |
| run_clients(0, _) -> ok; | |
| run_clients(Num, Server) -> | |
| spawn(?MODULE, client, [Num, Server]), | |
| run_clients(Num - 1, ServerPid). |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment