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-module(couch_proc_manager).
-behaviour(gen_server).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-export([start_link/0, get_proc_count/0]).
-include("couch_db.hrl").
-record(state, {tab}).
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
get_proc_count() ->
gen_server:call(?MODULE, get_proc_count).
init([]) ->
process_flag(trap_exit, true),
{ok, #state{tab = ets:new(procs, [{keypos, #proc.pid}])}}.
handle_call(get_table, _From, State) ->
{reply, State#state.tab, State};
handle_call(get_proc_count, _From, State) ->
{reply, ets:info(State#state.tab, size), State};
handle_call({get_proc, #doc{body={Props}}=DDoc, DDocKey}, {Client, _}, State) ->
Lang = couch_util:get_value(<<"language">>, Props, <<"javascript">>),
try get_procs(State#state.tab, Lang) of
Procs ->
case proc_with_ddoc(DDoc, DDocKey, Procs) of
{ok, Proc0} ->
Proc = Proc0#proc{client = erlang:monitor(process, Client)},
ets:insert(State#state.tab, Proc),
{reply, {ok, Proc, get_query_server_config()}, State};
{error, Reason} ->
{reply, {error, Reason}, State}
end
catch {unknown_query_language, _} ->
{reply, {unknown_query_language, Lang}, State};
error:Reason ->
?LOG_ERROR("~p ~p ~p", [?MODULE, Reason, erlang:get_stacktrace()]),
{reply, {error, Reason}, State}
end;
handle_call({get_proc, Lang}, {Client, _}, State) ->
try get_procs(State#state.tab, Lang) of
[Proc0|_] ->
Proc = Proc0#proc{client = erlang:monitor(process, Client)},
ets:insert(State#state.tab, Proc),
{reply, {ok, Proc, get_query_server_config()}, State}
catch {unknown_query_language, _} ->
{reply, {unknown_query_language, Lang}, State};
error:Reason ->
?LOG_ERROR("~p ~p ~p", [?MODULE, Reason, erlang:get_stacktrace()]),
{reply, {error, Reason}, State}
end;
handle_call({ret_proc, #proc{client=Ref, pid=Pid} = Proc}, _From, State) ->
erlang:demonitor(Ref, [flush]),
% We need to check if the process is alive here, as the client could be
% handing us a #proc{} with a dead one. We would have already removed the
% #proc{} from our own table, so the alternative is to do a lookup in the
% table before the insert. Don't know which approach is cheaper.
case is_process_alive(Pid) of true ->
maybe_reuse_proc(State#state.tab, Proc);
false -> ok end,
{reply, true, State};
handle_call(_Call, _From, State) ->
{reply, ignored, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info({'EXIT', Pid, Reason}, State) ->
?LOG_INFO("~p ~p died ~p", [?MODULE, Pid, Reason]),
ets:delete(State#state.tab, Pid),
{noreply, State};
handle_info({'DOWN', Ref, _, _, _Reason}, State) ->
case ets:match_object(State#state.tab, #proc{client=Ref, _='_'}) of
[] ->
ok;
[#proc{pid = Pid} = Proc] ->
case is_process_alive(Pid) of true ->
maybe_reuse_proc(State#state.tab, Proc);
false -> ok end
end,
{noreply, State};
handle_info(_Msg, State) ->
{noreply, State}.
terminate(_Reason, #state{tab=Tab}) ->
ets:foldl(fun(#proc{pid=P}, _) -> couch_util:shutdown_sync(P) end, 0, Tab),
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
maybe_reuse_proc(Tab, #proc{pid = Pid} = Proc) ->
Limit = couch_config:get("query_server_config", "os_process_soft_limit", "100"),
case ets:info(Tab, size) > list_to_integer(Limit) of
true ->
ets:delete(Tab, Pid),
unlink(Pid),
exit(Pid, kill);
false ->
garbage_collect(Pid),
ets:insert(Tab, Proc#proc{client=nil})
end.
get_procs(Tab, Lang) when is_binary(Lang) ->
get_procs(Tab, binary_to_list(Lang));
get_procs(Tab, Lang) when is_list(Lang) ->
case ets:match_object(Tab, #proc{lang=Lang, client=nil, _='_'}) of
[] ->
{ok, NewProc} = new_proc(Lang), % check OS process limit
[NewProc];
Procs ->
Procs
end.
new_proc(Lang) when is_list(Lang) ->
case couch_config:get("query_servers", Lang) of
undefined ->
case couch_config:get("native_query_servers", Lang) of
undefined ->
throw({unknown_query_language, Lang});
SpecStr ->
{ok, {M,F,A}} = couch_util:parse_term(SpecStr),
{ok, Pid} = apply(M, F, A),
make_proc(Pid, Lang, M)
end;
Command ->
{ok, Pid} = couch_os_process:start_link(Command),
make_proc(Pid, Lang, couch_os_process)
end.
make_proc(Pid, Lang, Mod) ->
Proc = #proc{
lang = Lang,
pid = Pid,
prompt_fun = {Mod, prompt},
set_timeout_fun = {Mod, set_timeout},
stop_fun = {Mod, stop}
},
{ok, Proc}.
get_query_server_config() ->
Limit = couch_config:get("query_server_config", <<"reduce_limit">>, "true"),
{[{<<"reduce_limit">>, list_to_atom(Limit)}]}.
proc_with_ddoc(DDoc, DDocKey, Procs) ->
Filter = fun(#proc{ddoc_keys=Keys}) -> not lists:member(DDocKey, Keys) end,
case lists:dropwhile(Filter, Procs) of
[DDocProc|_] ->
{ok, DDocProc};
[] ->
teach_any_proc(DDoc, DDocKey, Procs)
end.
teach_any_proc(DDoc, DDocKey, [Proc|Rest]) ->
try
teach_ddoc(DDoc, DDocKey, Proc)
catch _:_ ->
teach_any_proc(DDoc, DDocKey, Rest)
end;
teach_any_proc(_, _, []) ->
{error, noproc}.
teach_ddoc(DDoc, {DDocId, _Rev}=DDocKey, #proc{ddoc_keys=Keys}=Proc) ->
% send ddoc over the wire
% we only share the rev with the client we know to update code
% but it only keeps the latest copy, per each ddoc, around.
true = couch_query_servers:proc_prompt(Proc, [<<"ddoc">>, <<"new">>,
DDocId, couch_doc:to_json_obj(DDoc, [])]),
% we should remove any other ddocs keys for this docid
% because the query server overwrites without the rev
Keys2 = [{D,R} || {D,R} <- Keys, D /= DDocId],
% add ddoc to the proc
{ok, Proc#proc{ddoc_keys=[DDocKey|Keys2]}}.
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