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% Copyright 2010 Cloudant
%
% Licensed under the Apache License, Version 2.0 (the "License"); you may not
% use this file except in compliance with the License. You may obtain a copy of
% the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
-module(rexi_server).
-behaviour(gen_server).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-export([start_link/0, init_p/2]).
-include_lib("eunit/include/eunit.hrl").
-record(st, {
workers = ets:new(workers, [private, {keypos,2}])
}).
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
init([]) ->
{ok, #st{}}.
handle_call(_Request, _From, St) ->
{reply, ignored, St}.
handle_cast({doit, From, MFA}, #st{workers=Workers} = St) ->
{LocalPid, Ref} = spawn_monitor(?MODULE, init_p, [From, MFA]),
{noreply, St#st{workers = add_worker({LocalPid, Ref, From}, Workers)}};
handle_cast({kill, FromRef}, #st{workers=Workers} = St) ->
case find_worker_from(FromRef, Workers) of
{Pid, KeyRef, {_, FromRef}} ->
erlang:demonitor(KeyRef),
exit(Pid, kill),
{noreply, St#st{workers = remove_worker(KeyRef, Workers)}};
false ->
{noreply, St}
end.
handle_info({'DOWN', Ref, process, _, normal}, #st{workers=Workers} = St) ->
{noreply, St#st{workers = remove_worker(Ref, Workers)}};
handle_info({'DOWN', Ref, process, Pid, Reason}, #st{workers=Workers} = St) ->
case find_worker(Ref, Workers) of
{Pid, Ref, From} ->
notify_caller(From, Reason),
{noreply, St#st{workers = remove_worker(Ref, Workers)}};
false ->
{noreply, St}
end;
handle_info(_Info, St) ->
{noreply, St}.
terminate(_Reason, St) ->
ets:foldl(fun({Pid, _, _}, _) -> exit(Pid,kill) end, nil, St#st.workers),
ok.
code_change(_OldVsn, St, _Extra) ->
{ok, St}.
%% @doc initializes a process started by rexi_server.
-spec init_p({pid(), reference()}, {atom(), atom(), list()}) -> any().
init_p(From, {M,F,A}) ->
put(rexi_from, From),
put(initial_call, {M,F,length(A)}),
try apply(M, F, A) catch _:Reason -> exit(Reason) end.
%% internal
add_worker(Worker, Tab) ->
ets:insert(Tab, Worker), Tab.
remove_worker(Ref, Tab) ->
ets:delete(Tab, Ref), Tab.
find_worker(Ref, Tab) ->
case ets:lookup(Tab, Ref) of [] -> false; [Worker] -> Worker end.
find_worker_from(Ref, Tab) ->
case ets:match_object(Tab, {'_', '_', {'_', Ref}}) of
[] ->
false;
[Worker] ->
Worker
end.
notify_caller({Caller, Ref}, Reason) ->
Caller ! {Ref, {rexi_EXIT, Reason}}.
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