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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/0]).
-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([reduce/3, rereduce/3,validate_doc_update/5,render_doc_form/5]).
% -export([test/0]).
-include("couch_db.hrl").
start_link() ->
gen_server:start_link({local, couch_query_servers}, couch_query_servers, [], []).
stop() ->
exit(whereis(couch_query_servers), close).
start_doc_map(Lang, Functions) ->
Pid = get_os_process(Lang),
lists:foreach(fun(FunctionSource) ->
true = couch_os_process:prompt(Pid, [<<"add_fun">>, FunctionSource])
end, Functions),
{ok, {Lang, Pid}}.
map_docs({_Lang, Pid}, Docs) ->
% send the documents
Results = lists:map(
fun(Doc) ->
Json = couch_doc:to_json_obj(Doc, []),
FunsResults = couch_os_process:prompt(Pid, [<<"map_doc">>, Json]),
% 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 the key, value pairs to tuples like
% [{Key1, Value1}, {Key2, Value2}]
lists:map(
fun(FunRs) ->
[list_to_tuple(FunResult) || FunResult <- FunRs]
end,
FunsResults)
end,
Docs),
{ok, Results}.
stop_doc_map(nil) ->
ok;
stop_doc_map({Lang, Pid}) ->
ok = ret_os_process(Lang, Pid).
group_reductions_results([]) ->
[];
group_reductions_results(List) ->
{Heads, Tails} = lists:foldl(
fun([H|T], {HAcc,TAcc}) ->
{[H|HAcc], [T|TAcc]}
end, {[], []}, List),
case Tails of
[[]|_] -> % no tails left
[Heads];
_ ->
[Heads | group_reductions_results(Tails)]
end.
rereduce(_Lang, [], _ReducedValues) ->
{ok, []};
rereduce(Lang, RedSrcs, ReducedValues) ->
Pid = get_os_process(Lang),
Grouped = group_reductions_results(ReducedValues),
Results = lists:zipwith(
fun(FunSrc, Values) ->
[true, [Result]] =
couch_os_process:prompt(Pid, [<<"rereduce">>, [FunSrc], Values]),
Result
end, RedSrcs, Grouped),
ok = ret_os_process(Lang, Pid),
{ok, Results}.
reduce(_Lang, [], _KVs) ->
{ok, []};
reduce(Lang, RedSrcs, KVs) ->
Pid = get_os_process(Lang),
[true, Results] = couch_os_process:prompt(Pid,
[<<"reduce">>, RedSrcs, KVs]),
ok = ret_os_process(Lang, Pid),
{ok, Results}.
validate_doc_update(Lang, FunSrc, EditDoc, DiskDoc, Ctx) ->
Pid = get_os_process(Lang),
JsonEditDoc = couch_doc:to_json_obj(EditDoc, [revs]),
JsonDiskDoc =
if DiskDoc == nil ->
null;
true ->
couch_doc:to_json_obj(DiskDoc, [revs])
end,
try couch_os_process:prompt(Pid,
[<<"validate">>, FunSrc, JsonEditDoc, JsonDiskDoc, Ctx]) of
1 ->
ok;
{[{<<"forbidden">>, Message}]} ->
throw({forbidden, Message});
{[{<<"unauthorized">>, Message}]} ->
throw({unauthorized, Message})
after
ok = ret_os_process(Lang, Pid)
end.
render_doc_form(Lang, FormSrc, Doc, Req, Db) ->
Pid = get_os_process(Lang),
JsonDoc = couch_doc:to_json_obj(Doc, [revs]),
JsonReq = couch_httpd_external:json_req_obj(Req, Db),
try couch_os_process:prompt(Pid, [<<"form">>, FormSrc, JsonDoc, JsonReq]) of
FormResp ->
FormResp
after
ok = ret_os_process(Lang, Pid)
end.
init([]) ->
% read config and register for configuration changes
% just stop if one of the config settings change. couch_server_sup
% will restart us and then we will pick up the new settings.
ok = couch_config:register(
fun("query_servers" ++ _, _) ->
?MODULE:stop()
end),
Langs = ets:new(couch_query_server_langs, [set, private]),
PidLangs = ets:new(couch_query_server_pid_langs, [set, private]),
Pids = ets:new(couch_query_server_procs, [set, private]),
InUse = ets:new(couch_query_server_used, [set, private]),
lists:foreach(fun({Lang, Command}) ->
true = ets:insert(Langs, {?l2b(Lang), Command})
end, couch_config:get("query_servers")),
{ok, {Langs, PidLangs, Pids, InUse}}.
terminate(_Reason, _Server) ->
ok.
handle_call({get_proc, Lang}, _From, {Langs, PidLangs, Pids, InUse}=Server) ->
% Note to future self. Add max process limit.
case ets:lookup(Pids, Lang) of
[{Lang, [Pid|_]}] ->
add_value(PidLangs, Pid, Lang),
rem_from_list(Pids, Lang, Pid),
add_to_list(InUse, Lang, Pid),
true = couch_os_process:prompt(Pid, [<<"reset">>]),
{reply, Pid, Server};
_ ->
{ok, Pid} = new_process(Langs, Lang),
add_to_list(InUse, Lang, Pid),
{reply, Pid, Server}
end;
handle_call({ret_proc, Lang, Pid}, _From, {_, _, Pids, InUse}=Server) ->
% Along with max process limit, here we should check
% if we're over the limit and discard when we are.
add_to_list(Pids, Lang, Pid),
rem_from_list(InUse, Lang, Pid),
{reply, true, Server}.
handle_cast(_Whatever, Server) ->
{noreply, Server}.
handle_info({'EXIT', Pid, Status}, {Langs, PidLangs, Pids, InUse}) ->
case ets:lookup(PidLangs, Pid) of
[{Pid, Lang}] ->
case Status of
normal -> ok;
_ -> ?LOG_DEBUG("Linked process died abnromally: ~p (reason: ~p)", [Pid, Status])
end,
{ok, {
Langs,
rem_value(PidLangs, Pid),
rem_from_list(Pids, Lang, Pid),
rem_from_list(InUse, Lang, Pid)
}};
[] ->
?LOG_DEBUG("Unknown linked process died: ~p (reason: ~p)", [Pid, Status]),
{ok, {Langs, PidLangs, Pids, InUse}}
end.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
% Private API
new_process(Langs, Lang) ->
Proc =
case ets:lookup(Langs, Lang) of
[{Lang, Command}] ->
couch_os_process:start_link(Command);
_ ->
throw({unknown_query_language, Lang})
end,
Proc.
get_os_process(Lang) ->
gen_server:call(couch_query_servers, {get_proc, Lang}).
ret_os_process(Lang, Pid) ->
true = gen_server:call(couch_query_servers, {ret_proc, Lang, Pid}),
ok.
add_value(Tid, Key, Value) ->
true = ets:insert(Tid, {Key, Value}).
rem_value(Tid, Key) ->
true = ets:insert(Tid, Key).
add_to_list(Tid, Key, Value) ->
case ets:lookup(Tid, Key) of
[{Key, Vals}] ->
true = ets:insert(Tid, {Key, [Value|Vals]});
[] ->
true = ets:insert(Tid, {Key, [Value]})
end.
rem_from_list(Tid, Key, Value) ->
case ets:lookup(Tid, Key) of
[{Key, Vals}] ->
ets:insert(Tid, {Key, [Val || Val <- Vals, Val /= Value]});
[] -> ok
end.
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