lib/etorrent-1.0/src/etorrent_counters.erl

   1 %%%-------------------------------------------------------------------
   2 %%% File    : etorrent_counters.erl
   3 %%% Author  : Jesper Louis Andersen <jlouis@ogre.home>
   4 %%% Description : Various global counters in etorrent
   5 %%%
   6 %%% Created : 29 Jul 2008 by Jesper Louis Andersen <jlouis@ogre.home>
   7 %%%-------------------------------------------------------------------
   8 -module(etorrent_counters).
   9
  10 -behaviour(gen_server).
  11
  12 %% API
  13 -export([start_link/0, next/1, obtain_peer_slot/0, release_peer_slot/0,
  14          max_peer_processes/0]).
  15
  16 %% gen_server callbacks
  17 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  18          terminate/2, code_change/3]).
  19
  20 -record(state, {}).
  21 -define(SERVER, ?MODULE).
  22 -define(MAX_PEER_PROCESSES, 40).
  23
  24 %%====================================================================
  25 %% API
  26 %%====================================================================
  27 %%--------------------------------------------------------------------
  28 %% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
  29 %% Description: Starts the server
  30 %%--------------------------------------------------------------------
  31 start_link() ->
  32     gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
  33
  34 next(Sequence) ->
  35     gen_server:call(?SERVER, {next, Sequence}).
  36
  37 obtain_peer_slot() ->
  38     gen_server:call(?SERVER, obtain_peer_slot).
  39
  40 release_peer_slot() ->
  41     gen_server:cast(?SERVER, release_peer_slot).
  42
  43 %%====================================================================
  44 %% gen_server callbacks
  45 %%====================================================================
  46
  47 %%--------------------------------------------------------------------
  48 %% Function: init(Args) -> {ok, State} |
  49 %%                         {ok, State, Timeout} |
  50 %%                         ignore               |
  51 %%                         {stop, Reason}
  52 %% Description: Initiates the server
  53 %%--------------------------------------------------------------------
  54 init([]) ->
  55     process_flag(trap_exit, true),
  56     _Tid = ets:new(etorrent_counters, [named_table, protected]),
  57     ets:insert(etorrent_counters, [{torrent, 0},
  58                                    {path_map, 0},
  59                                    {peer_slots, 0}]),
  60     {ok, #state{}}.
  61
  62 %%--------------------------------------------------------------------
  63 %% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
  64 %%                                      {reply, Reply, State, Timeout} |
  65 %%                                      {noreply, State} |
  66 %%                                      {noreply, State, Timeout} |
  67 %%                                      {stop, Reason, Reply, State} |
  68 %%                                      {stop, Reason, State}
  69 %% Description: Handling call messages
  70 %%--------------------------------------------------------------------
  71 handle_call({next, Seq}, _From, S) ->
  72     N = ets:update_counter(etorrent_counters, Seq, 1),
  73     {reply, N, S};
  74 handle_call(obtain_peer_slot, _From, S) ->
  75     [{peer_slots, K}] = ets:lookup(etorrent_counters, peer_slots),
  76     case K >= max_peer_processes() of
  77         true ->
  78             {reply, full, S};
  79         false ->
  80             ets:update_counter(etorrent_counters, peer_slots, 1),
  81             {reply, ok, S}
  82     end;
  83 handle_call(_Request, _From, State) ->
  84     Reply = ok,
  85     {reply, Reply, State}.
  86
  87 %%--------------------------------------------------------------------
  88 %% Function: handle_cast(Msg, State) -> {noreply, State} |
  89 %%                                      {noreply, State, Timeout} |
  90 %%                                      {stop, Reason, State}
  91 %% Description: Handling cast messages
  92 %%--------------------------------------------------------------------
  93 handle_cast(release_peer_slot, S) ->
  94     K = ets:update_counter(etorrent_counters, peer_slots, -1),
  95     true = K >= 0,
  96     {noreply, S};
  97 handle_cast(_Msg, State) ->
  98     {noreply, State}.
  99
 100 %%--------------------------------------------------------------------
 101 %% Function: handle_info(Info, State) -> {noreply, State} |
 102 %%                                       {noreply, State, Timeout} |
 103 %%                                       {stop, Reason, State}
 104 %% Description: Handling all non call/cast messages
 105 %%--------------------------------------------------------------------
 106 handle_info(_Info, State) ->
 107     {noreply, State}.
 108
 109 %%--------------------------------------------------------------------
 110 %% Function: terminate(Reason, State) -> void()
 111 %% Description: This function is called by a gen_server when it is about to
 112 %% terminate. It should be the opposite of Module:init/1 and do any necessary
 113 %% cleaning up. When it returns, the gen_server terminates with Reason.
 114 %% The return value is ignored.
 115 %%--------------------------------------------------------------------
 116 terminate(_Reason, _State) ->
 117     true = ets:delete(etorrent_counters),
 118     ok.
 119
 120 %%--------------------------------------------------------------------
 121 %% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
 122 %% Description: Convert process state when code is changed
 123 %%--------------------------------------------------------------------
 124 code_change(_OldVsn, State, _Extra) ->
 125     {ok, State}.
 126
 127 %%--------------------------------------------------------------------
 128 %%% Internal functions
 129 %%--------------------------------------------------------------------
 130 max_peer_processes() ->
 131     case application:get_env(etorrent, max_peers) of
 132         {ok, N} when is_integer(N) ->
 133             N;
 134         undefined ->
 135             ?MAX_PEER_PROCESSES
 136     end.