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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).
-export([start/0, stop/0, restart/0]).
-export([cast/2, cast/3, kill/2]).
-export([reply/1, sync_reply/1, sync_reply/2]).
-export([async_server_call/2, async_server_call/3]).
-define(SERVER, rexi_server).
start() ->
application:start(rexi).
stop() ->
application:stop(rexi).
restart() ->
stop(), start().
%% @equiv cast(Node, self(), MFA)
-spec cast(node(), {atom(), atom(), list()}) -> reference().
cast(Node, MFA) ->
cast(Node, self(), MFA).
%% @doc Executes apply(M, F, A) on Node.
%% You might want to use this instead of rpc:cast/4 for two reasons. First,
%% the Caller pid and the returned reference are inserted into the remote
%% process' dictionary as `rexi_from', so it has a way to communicate with you.
%% Second, the remote process is monitored. If it exits with a Reason other
%% than normal, Caller will receive a message of the form
%% `{Ref, {rexi_EXIT, Reason}}' where Ref is the returned reference.
-spec cast(node(), pid(), {atom(), atom(), list()}) -> reference().
cast(Node, Caller, MFA) ->
Ref = make_ref(),
ok = gen_server:cast({?SERVER, Node}, {doit, {Caller,Ref}, MFA}),
Ref.
%% @doc Sends an async kill signal to the remote process associated with Ref.
%% No rexi_EXIT message will be sent.
-spec kill(node(), reference()) -> ok.
kill(Node, Ref) ->
ok = gen_server:cast({?SERVER, Node}, {kill, Ref}).
%% @equiv async_server_call(Server, self(), Request)
-spec async_server_call(pid() | {atom(),node()}, any()) -> reference().
async_server_call(Server, Request) ->
async_server_call(Server, self(), Request).
%% @doc Sends a properly formatted gen_server:call Request to the Server and
%% returns the reference which the Server will include in its reply. The
%% function acts more like cast() than call() in that the server process
%% is not monitored. Clients who want to know if the server is alive should
%% monitor it themselves before calling this function.
-spec async_server_call(pid() | {atom(),node()}, pid(), any()) -> reference().
async_server_call(Server, Caller, Request) ->
Ref = make_ref(),
do_send(Server, {'$gen_call', {Caller,Ref}, Request}),
Ref.
%% @doc convenience function to reply to the original rexi Caller.
-spec reply(any()) -> any().
reply(Reply) ->
{Caller, Ref} = get(rexi_from),
erlang:send(Caller, {Ref,Reply}).
%% @equiv sync_reply(Reply, 300000)
sync_reply(Reply) ->
sync_reply(Reply, 300000).
%% @doc convenience function to reply to caller and wait for response. Message
%% is of the form {OriginalRef, {self(),reference()}, Reply}, which enables the
%% original caller to respond back.
-spec sync_reply(any(), pos_integer() | infinity) -> any().
sync_reply(Reply, Timeout) ->
{Caller, Ref} = get(rexi_from),
Tag = make_ref(),
erlang:send(Caller, {Ref, {self(),Tag}, Reply}),
receive {Tag, Response} ->
Response
after Timeout ->
timeout
end.
%% internal functions %%
% send a message as quickly as possible
do_send(Dest, Msg) ->
case erlang:send(Dest, Msg, [noconnect]) of
noconnect ->
spawn(erlang, send, [Dest, Msg]);
ok ->
ok
end.
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