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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_query_servers).
-behaviour(gen_server).
-export([start_link/1]).
-export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2,code_change/3,stop/0]).
-export([start_doc_map/2, map_docs/2, stop_doc_map/1]).
-export([test/0, test/1]).
-include("couch_db.hrl").
timeout() ->
% hardcoded 5 sec timeout per document
5000.
start_link(QueryServerList) ->
gen_server:start_link({local, couch_query_servers}, couch_query_servers, QueryServerList, []).
stop() ->
exit(whereis(couch_query_servers), close).
readline(Port) ->
readline(Port, []).
readline(Port, Acc) ->
Timer = erlang:send_after(timeout(), self(), timeout),
Result =
receive
{Port, {data, {noeol, Data}}} ->
readline(Port, [Data|Acc]);
{Port, {data, {eol, Data}}} ->
lists:flatten(lists:reverse(Acc, Data));
{Port, Err} ->
catch port_close(Port),
erlang:cancel_timer(Timer),
throw({map_process_error, Err});
timeout ->
catch port_close(Port),
throw({map_process_error, "map function timed out"})
end,
case erlang:cancel_timer(Timer) of
false ->
% message already sent. clear it
receive timeout -> ok end;
_ ->
ok
end,
Result.
read_json(Port) ->
case cjson:decode(readline(Port)) of
{obj, [{"log", Msg}]} when is_list(Msg) ->
% we got a message to log. Log it and continue
couch_log:info("Query Server Log Message: ~s", [Msg]),
read_json(Port);
Else ->
Else
end.
writeline(Port, String) ->
true = port_command(Port, String ++ "\n").
% send command and get a response.
prompt(Port, Json) ->
writeline(Port, cjson:encode(Json)),
read_json(Port).
start_doc_map(Lang, Functions) ->
Port =
case gen_server:call(couch_query_servers, {get_port, Lang}) of
{ok, Port0} ->
link(Port0),
Port0;
{empty, Cmd} ->
couch_log:info("Spawning new ~s instance.", [Lang]),
open_port({spawn, Cmd}, [stream,
{line, 1000},
exit_status,
hide]);
Error ->
throw(Error)
end,
true = prompt(Port, {"reset"}),
% send the functions as json strings
lists:foreach(fun(FunctionSource) ->
case prompt(Port, {"add_fun", FunctionSource}) of
true -> ok;
{obj, [{"error", Id}, {"reason", Reason}]} ->
throw({Id, Reason})
end
end,
Functions),
{ok, {Lang, Port}}.
map_docs({_Lang, Port}, Docs) ->
% send the documents
Results =
lists:map(
fun(Doc) ->
Json = couch_doc:to_json_obj(Doc, []),
case prompt(Port, {"map_doc", Json}) of
{obj, [{"error", Id}, {"reason", Reason}]} ->
throw({list_to_atom(Id),Reason});
{obj, [{"reason", Reason}, {"error", Id}]} ->
throw({list_to_atom(Id),Reason});
Results when is_tuple(Results) ->
% the results are a json array of function map yields like this:
% {FunResults1, FunResults2 ...}
% where funresults is are json arrays of key value pairs:
% {{Key1, Value1}, {Key2, Value2}}
% Convert to real lists, execept the key, value pairs
[tuple_to_list(FunResult) || FunResult <- tuple_to_list(Results)]
end
end,
Docs),
{ok, Results}.
stop_doc_map(nil) ->
ok;
stop_doc_map({Lang, Port}) ->
ok = gen_server:call(couch_query_servers, {return_port, {Lang, Port}}),
true = unlink(Port),
ok.
init(QueryServerList) ->
{ok, {QueryServerList, []}}.
terminate(_Reason, _Server) ->
ok.
handle_call({get_port, Lang}, {FromPid, _}, {QueryServerList, LangPorts}) ->
case lists:keysearch(Lang, 1, LangPorts) of
{value, {_, Port}=LangPort} ->
Result =
case catch port_connect(Port, FromPid) of
true ->
true = unlink(Port),
{ok, Port};
Error ->
catch port_close(Port),
Error
end,
{reply, Result, {QueryServerList, LangPorts -- [LangPort]}};
false ->
case lists:keysearch(Lang, 1, QueryServerList) of
{value, {_, ServerCmd}} ->
{reply, {empty, ServerCmd}, {QueryServerList, LangPorts}};
false -> % not a supported language
{reply, {query_language_unknown, Lang}, {QueryServerList, LangPorts}}
end
end;
handle_call({return_port, {Lang, Port}}, _From, {QueryServerList, LangPorts}) ->
case catch port_connect(Port, self()) of
true ->
{reply, ok, {QueryServerList, [{Lang, Port} | LangPorts]}};
_ ->
catch port_close(Port),
{reply, ok, {QueryServerList, LangPorts}}
end.
handle_cast(_Whatever, {Cmd, Ports}) ->
{noreply, {Cmd, Ports}}.
handle_info({Port, {exit_status, Status}}, {QueryServerList, LangPorts}) ->
case lists:keysearch(Port, 2, LangPorts) of
{value, {Lang, _}} ->
case Status of
0 -> ok;
_ -> couch_log:error("Abnormal shutdown of ~s query server process (exit_status: ~w).", [Lang, Status])
end,
{noreply, {QueryServerList, lists:keydelete(Port, 2, LangPorts)}};
_ ->
couch_log:error("Unknown linked port/process crash: ~p", [Port])
end;
handle_info(_Whatever, {Cmd, Ports}) ->
{noreply, {Cmd, Ports}}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
test() ->
test("../js/js -f main.js").
test(Cmd) ->
start_link(Cmd),
{ok, DocMap} = start_doc_map("javascript", ["function(doc) {if (doc[0] == 'a') return doc[1];}"]),
{ok, Results} = map_docs(DocMap, [#doc{body={"a", "b"}}, #doc{body={"c", "d"}},#doc{body={"a", "c"}}]),
io:format("Results: ~w~n", [Results]),
stop_doc_map(DocMap),
ok.
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