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+%% Copyright (c) 2011-2012, Loïc Hoguin <essen@ninenines.eu>
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+%%
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+%% Permission to use, copy, modify, and/or distribute this software for any
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+%% purpose with or without fee is hereby granted, provided that the above
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+%% copyright notice and this permission notice appear in all copies.
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+%%
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+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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+
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+%% @doc Public API for managing listeners.
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+-module(ranch_listener).
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+-behaviour(gen_server).
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+
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+-export([start_link/2, stop/1,
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+ add_connection/4, move_connection/3, remove_connection/2, check_upgrades/2,
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+ get_protocol_options/1, set_protocol_options/2]). %% API.
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+-export([init/1, handle_call/3, handle_cast/2,
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+ handle_info/2, terminate/2, code_change/3]). %% gen_server.
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+
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+-type pools() :: [{atom(), non_neg_integer()}].
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+
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+-record(state, {
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+ conn_pools = [] :: pools(),
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+ conns_table :: ets:tid(),
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+ queue = undefined :: queue(),
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+ max_conns = undefined :: non_neg_integer(),
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+ proto_opts :: any(),
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+ proto_opts_vsn = 1 :: non_neg_integer()
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+}).
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+
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+%% API.
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+
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+%% @private
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+%%
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+%% We set the process priority to high because ranch_listener is the central
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+%% gen_server in Ranch and is used to manage all the incoming connections.
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+%% Setting the process priority to high ensures the connection-related code
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+%% will always be executed when a connection needs it, allowing Ranch to
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+%% scale far beyond what it would with a normal priority.
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+-spec start_link(non_neg_integer(), any()) -> {ok, pid()}.
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+start_link(MaxConns, ProtoOpts) ->
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+ gen_server:start_link(?MODULE, [MaxConns, ProtoOpts],
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+ [{spawn_opt, [{priority, high}]}]).
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+
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+%% @private
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+-spec stop(pid()) -> stopped.
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+stop(ServerPid) ->
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+ gen_server:call(ServerPid, stop).
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+
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+%% @doc Add a connection to the given pool in the listener.
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+%%
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+%% Pools of connections are used to restrict the maximum number of connections
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+%% depending on their type. By default, Ranch add all connections to the
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+%% pool <em>default</em>. It also checks for the maximum number of connections
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+%% in that pool before accepting again. This function only returns when there
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+%% is free space in the pool.
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+%%
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+%% When a process managing a connection dies, the process is removed from the
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+%% pool. If the socket has been sent to another process, it is up to the
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+%% protocol code to inform the listener of the new <em>ConnPid</em> by removing
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+%% the previous and adding the new one.
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+%%
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+%% This function also returns whether the protocol options have been modified.
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+%% If so, then an {upgrade, ProtoOpts, OptsVsn} will be returned instead of
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+%% the atom 'ok'. The acceptor can then continue with the new protocol options.
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+-spec add_connection(pid(), atom(), pid(), non_neg_integer())
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+ -> ok | {upgrade, any(), non_neg_integer()}.
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+add_connection(ServerPid, Pool, ConnPid, OptsVsn) ->
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+ gen_server:call(ServerPid, {add_connection, Pool, ConnPid, OptsVsn},
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+ infinity).
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+
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+%% @doc Move a connection from one pool to another.
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+-spec move_connection(pid(), atom(), pid()) -> ok.
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+move_connection(ServerPid, DestPool, ConnPid) ->
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+ gen_server:cast(ServerPid, {move_connection, DestPool, ConnPid}).
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+
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+%% @doc Remove the given connection from its pool.
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+-spec remove_connection(pid(), pid()) -> ok.
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+remove_connection(ServerPid, ConnPid) ->
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+ gen_server:cast(ServerPid, {remove_connection, ConnPid}).
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+
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+%% @doc Return whether a protocol upgrade is required.
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+-spec check_upgrades(pid(), non_neg_integer())
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+ -> ok | {upgrade, any(), non_neg_integer()}.
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+check_upgrades(ServerPid, OptsVsn) ->
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+ gen_server:call(ServerPid, {check_upgrades, OptsVsn}).
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+
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+%% @doc Return the current protocol options.
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+-spec get_protocol_options(pid()) -> {ok, any()}.
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+get_protocol_options(ServerPid) ->
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+ gen_server:call(ServerPid, get_protocol_options).
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+
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+%% @doc Upgrade the protocol options.
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+-spec set_protocol_options(pid(), any()) -> ok.
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+set_protocol_options(ServerPid, ProtoOpts) ->
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+ gen_server:call(ServerPid, {set_protocol_options, ProtoOpts}).
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+
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+%% gen_server.
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+
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+%% @private
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+-spec init(list()) -> {ok, #state{}}.
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+init([MaxConns, ProtoOpts]) ->
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+ ConnsTable = ets:new(connections_table, [set, private]),
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+ Queue = queue:new(),
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+ {ok, #state{conns_table=ConnsTable, max_conns=MaxConns,
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+ proto_opts=ProtoOpts, queue=Queue}}.
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+
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+%% @private
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+-spec handle_call(_, _, State)
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+ -> {reply, ignored, State} | {stop, normal, stopped, State}.
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+handle_call({add_connection, Pool, ConnPid, AccOptsVsn}, From, State=#state{
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+ conn_pools=Pools, conns_table=ConnsTable,
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+ queue=Queue, max_conns=MaxConns,
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+ proto_opts=ProtoOpts, proto_opts_vsn=LisOptsVsn}) ->
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+ {NbConns, Pools2} = add_pid(ConnPid, Pool, Pools, ConnsTable),
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+ State2 = State#state{conn_pools=Pools2},
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+ if AccOptsVsn =/= LisOptsVsn ->
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+ {reply, {upgrade, ProtoOpts, LisOptsVsn}, State2};
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+ NbConns > MaxConns ->
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+ Queue2 = queue:in(From, Queue),
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+ {noreply, State2#state{queue=Queue2}};
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+ true ->
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+ {reply, ok, State2}
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+ end;
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+handle_call({check_upgrades, AccOptsVsn}, _From, State=#state{
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+ proto_opts=ProtoOpts, proto_opts_vsn=LisOptsVsn}) ->
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+ if AccOptsVsn =/= LisOptsVsn ->
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+ {reply, {upgrade, ProtoOpts, LisOptsVsn}, State};
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+ true ->
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+ {reply, ok, State}
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+ end;
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+handle_call(get_protocol_options, _From, State=#state{proto_opts=ProtoOpts}) ->
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+ {reply, {ok, ProtoOpts}, State};
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+handle_call({set_protocol_options, ProtoOpts}, _From,
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+ State=#state{proto_opts_vsn=OptsVsn}) ->
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+ {reply, ok, State#state{proto_opts=ProtoOpts, proto_opts_vsn=OptsVsn + 1}};
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+handle_call(stop, _From, State) ->
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+ {stop, normal, stopped, State};
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+handle_call(_, _From, State) ->
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+ {reply, ignored, State}.
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+
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+%% @private
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+-spec handle_cast(_, State) -> {noreply, State}.
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+handle_cast({move_connection, DestPool, ConnPid}, State=#state{
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+ conn_pools=Pools, conns_table=ConnsTable}) ->
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+ Pools2 = move_pid(ConnPid, DestPool, Pools, ConnsTable),
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+ {noreply, State#state{conn_pools=Pools2}};
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+handle_cast({remove_connection, ConnPid}, State=#state{
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+ conn_pools=Pools, conns_table=ConnsTable, queue=Queue}) ->
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+ {Pools2, Queue2} = remove_pid(ConnPid, Pools, ConnsTable, Queue),
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+ {noreply, State#state{conn_pools=Pools2, queue=Queue2}};
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+handle_cast(_Msg, State) ->
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+ {noreply, State}.
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+
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+%% @private
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+-spec handle_info(_, State) -> {noreply, State}.
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+handle_info({'DOWN', _Ref, process, Pid, _Info}, State=#state{
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+ conn_pools=Pools, conns_table=ConnsTable, queue=Queue}) ->
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+ {Pools2, Queue2} = remove_pid(Pid, Pools, ConnsTable, Queue),
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+ {noreply, State#state{conn_pools=Pools2, queue=Queue2}};
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+handle_info(_Info, State) ->
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+ {noreply, State}.
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+
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+%% @private
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+-spec terminate(_, _) -> ok.
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+terminate(_Reason, _State) ->
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+ ok.
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+
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+%% @private
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+-spec code_change(_, State, _) -> {ok, State}.
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+code_change(_OldVsn, State, _Extra) ->
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+ {ok, State}.
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+
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+%% Internal.
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+
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+%% @private
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+-spec add_pid(pid(), atom(), pools(), ets:tid())
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+ -> {non_neg_integer(), pools()}.
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+add_pid(ConnPid, Pool, Pools, ConnsTable) ->
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+ MonitorRef = erlang:monitor(process, ConnPid),
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+ ConnPid ! {shoot, self()},
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+ {NbConnsRet, Pools2} = case lists:keyfind(Pool, 1, Pools) of
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+ false ->
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+ {1, [{Pool, 1}|Pools]};
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+ {Pool, NbConns} ->
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+ NbConns2 = NbConns + 1,
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+ {NbConns2, [{Pool, NbConns2}|lists:keydelete(Pool, 1, Pools)]}
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+ end,
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+ ets:insert(ConnsTable, {ConnPid, {MonitorRef, Pool}}),
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+ {NbConnsRet, Pools2}.
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+
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+%% @private
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+-spec move_pid(pid(), atom(), pools(), ets:tid()) -> pools().
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+move_pid(ConnPid, DestPool, Pools, ConnsTable) ->
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+ {MonitorRef, SrcPool} = ets:lookup_element(ConnsTable, ConnPid, 2),
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+ ets:insert(ConnsTable, {ConnPid, {MonitorRef, DestPool}}),
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+ {SrcPool, SrcNbConns} = lists:keyfind(SrcPool, 1, Pools),
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+ DestNbConns = case lists:keyfind(DestPool, 1, Pools) of
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+ false -> 1;
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+ {DestPool, NbConns} -> NbConns + 1
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+ end,
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+ Pools2 = lists:keydelete(SrcPool, 1, lists:keydelete(DestPool, 1, Pools)),
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+ [{SrcPool, SrcNbConns - 1}, {DestPool, DestNbConns}|Pools2].
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+
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+%% @private
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+-spec remove_pid(pid(), pools(), ets:tid(), queue()) -> {pools(), queue()}.
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+remove_pid(Pid, Pools, ConnsTable, Queue) ->
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+ {MonitorRef, Pool} = ets:lookup_element(ConnsTable, Pid, 2),
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+ erlang:demonitor(MonitorRef, [flush]),
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+ {Pool, NbConns} = lists:keyfind(Pool, 1, Pools),
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+ Pools2 = [{Pool, NbConns - 1}|lists:keydelete(Pool, 1, Pools)],
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+ ets:delete(ConnsTable, Pid),
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+ case queue:out(Queue) of
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+ {{value, Client}, Queue2} ->
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+ gen_server:reply(Client, ok),
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+ {Pools2, Queue2};
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+ _ ->
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+ {Pools2, Queue}
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+ end.
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