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% 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(couch_os_process).
-behaviour(gen_server).
-export([start_link/1, start_link/2, start_link/3, stop/1]).
-export([set_timeout/2, prompt/2]).
-export([send/2, writeline/2, readline/1, writejson/2, readjson/1]).
-export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2, code_change/3]).
-include("couch_db.hrl").
-define(PORT_OPTIONS, [stream, {line, 1024}, binary, exit_status, hide]).
-record(os_proc,
{command,
port,
writer,
reader,
timeout=5000
}).
start_link(Command) ->
start_link(Command, []).
start_link(Command, Options) ->
start_link(Command, Options, ?PORT_OPTIONS).
start_link(Command, Options, PortOptions) ->
gen_server:start_link(couch_os_process, [Command, Options, PortOptions], []).
stop(Pid) ->
gen_server:cast(Pid, stop).
% Read/Write API
set_timeout(Pid, TimeOut) when is_integer(TimeOut) ->
ok = gen_server:call(Pid, {set_timeout, TimeOut}).
% Used by couch_db_update_notifier.erl
send(Pid, Data) ->
gen_server:cast(Pid, {send, Data}).
prompt(Pid, Data) ->
case gen_server:call(Pid, {prompt, Data}, infinity) of
{ok, Result} ->
Result;
Error ->
?LOG_ERROR("OS Process Error ~p :: ~p",[Pid,Error]),
throw(Error)
end.
% Utility functions for reading and writing
% in custom functions
writeline(#os_proc{port=Port}, Data) ->
port_command(Port, Data ++ "\n").
readline(#os_proc{} = OsProc) ->
readline(OsProc, []).
readline(#os_proc{port=Port, timeout=Timeout} = OsProc, Acc) ->
receive
{Port, {data, {noeol, Data}}} ->
readline(OsProc, [Data|Acc]);
{Port, {data, {eol, Data}}} ->
lists:reverse(Acc, Data);
{Port, Err} ->
catch port_close(Port),
throw({os_process_error, Err})
after Timeout ->
catch port_close(Port),
throw({os_process_error, "OS process timed out."})
end.
% Standard JSON functions
writejson(OsProc, Data) when is_record(OsProc, os_proc) ->
JsonData = ?JSON_ENCODE(Data),
% ?LOG_DEBUG("OS Process ~p Input :: ~s", [OsProc#os_proc.port, JsonData]),
true = writeline(OsProc, JsonData).
readjson(#os_proc{} = OsProc) ->
Line = readline(OsProc),
% ?LOG_DEBUG("OS Process ~p Output :: ~s", [OsProc#os_proc.port, Line]),
case ?JSON_DECODE(Line) of
[<<"log">>, Msg] when is_binary(Msg) ->
% we got a message to log. Log it and continue
?LOG_INFO("OS Process ~p Log :: ~s", [OsProc#os_proc.port, Msg]),
readjson(OsProc);
[<<"error">>, Id, Reason] ->
throw({couch_util:to_existing_atom(Id),Reason});
[<<"fatal">>, Id, Reason] ->
?LOG_INFO("OS Process ~p Fatal Error :: ~s ~p",[OsProc#os_proc.port, Id, Reason]),
throw({couch_util:to_existing_atom(Id),Reason});
Result ->
Result
end.
% gen_server API
init([Command, Options, PortOptions]) ->
Spawnkiller = filename:join([code:priv_dir(couch), "couchspawnkillable.sh"]),
BaseProc = #os_proc{
command=Command,
port=open_port({spawn, Spawnkiller ++ " " ++ Command}, PortOptions),
writer=fun writejson/2,
reader=fun readjson/1
},
KillCmd = readline(BaseProc),
Pid = self(),
% ?LOG_DEBUG("OS Process Start :: ~p", [BaseProc#os_proc.port]),
spawn(fun() ->
% this ensure the real os process is killed when this process dies.
erlang:monitor(process, Pid),
receive _ -> ok end,
os:cmd(?b2l(KillCmd))
end),
OsProc =
lists:foldl(fun(Opt, Proc) ->
case Opt of
{writer, Writer} when is_function(Writer) ->
Proc#os_proc{writer=Writer};
{reader, Reader} when is_function(Reader) ->
Proc#os_proc{reader=Reader};
{timeout, TimeOut} when is_integer(TimeOut) ->
Proc#os_proc{timeout=TimeOut}
end
end, BaseProc, Options),
{ok, OsProc}.
terminate(_Reason, #os_proc{port=Port}) ->
catch port_close(Port),
ok.
handle_call({set_timeout, TimeOut}, _From, OsProc) ->
{reply, ok, OsProc#os_proc{timeout=TimeOut}};
handle_call({prompt, Data}, _From, OsProc) ->
#os_proc{writer=Writer, reader=Reader} = OsProc,
try
Writer(OsProc, Data),
{reply, {ok, Reader(OsProc)}, OsProc}
catch
throw:{error, OsError} ->
{reply, OsError, OsProc};
throw:{fatal, OsError} ->
{stop, normal, OsError, OsProc};
throw:OtherError ->
{stop, normal, OtherError, OsProc}
end.
handle_cast({send, Data}, #os_proc{writer=Writer}=OsProc) ->
try
Writer(OsProc, Data),
{noreply, OsProc}
catch
throw:OsError ->
?LOG_ERROR("Failed sending data: ~p -> ~p", [Data, OsError]),
{stop, normal, OsProc}
end;
handle_cast(stop, OsProc) ->
{stop, normal, OsProc};
handle_cast(Msg, OsProc) ->
?LOG_DEBUG("OS Proc: Unknown cast: ~p", [Msg]),
{noreply, OsProc}.
handle_info({Port, {exit_status, 0}}, #os_proc{port=Port}=OsProc) ->
?LOG_INFO("OS Process terminated normally", []),
{stop, normal, OsProc};
handle_info({Port, {exit_status, Status}}, #os_proc{port=Port}=OsProc) ->
?LOG_ERROR("OS Process died with status: ~p", [Status]),
{stop, {exit_status, Status}, OsProc}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
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