Created
January 13, 2016 10:01
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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_view_merger_queue). | |
% TODO: try to simplify this module, taking into account efficient/practical | |
% use by couch_view_merger.erl | |
% public API | |
-export([start_link/2]). | |
% consumer API | |
-export([pop/1, pop_next/1, peek/1, flush/1]). | |
% producer API | |
-export([queue/2, done/1]). | |
% gen_server callbacks | |
-export([init/1, handle_call/3, handle_info/2, handle_cast/2]). | |
-export([code_change/3, terminate/2]). | |
-include("couch_db.hrl"). | |
-record(state, { | |
rows, % a functional priority queue (skew) | |
poped = [], % list of so far poped items | |
consumer = nil, % pop request (only 1 consumer is supported) | |
less_fun, | |
num_producers | |
}). | |
start_link(NumProducers, LessFun) when is_integer(NumProducers), NumProducers > 0 -> | |
gen_server:start_link(?MODULE, {NumProducers, LessFun}, []). | |
pop(Pid) -> | |
try | |
gen_server:call(Pid, pop, infinity) | |
catch | |
exit:{shutdown, {gen_server, call, [Pid | _]}} -> | |
closed; | |
exit:{noproc, {gen_server, call, [Pid | _]}} -> | |
closed; | |
exit:{normal, {gen_server, call, [Pid | _]}} -> | |
closed | |
end. | |
pop_next(Pid) -> | |
gen_server:call(Pid, pop_next, infinity). | |
peek(Pid) -> | |
gen_server:call(Pid, peek). | |
queue(Pid, Row) -> | |
NextRef = make_ref(), | |
case wait_previous_row_processed(Pid) of | |
{ok, MonRef} -> | |
receive | |
{'DOWN', MonRef, _, _, _} -> | |
throw(queue_shutdown) | |
after 0 -> | |
erlang:demonitor(MonRef, [flush]), | |
ok = gen_server:cast(Pid, {queue, Row, self(), NextRef}), | |
erlang:put(queue_ref, NextRef) | |
end, | |
ok; | |
closed -> | |
throw(queue_shutdown) | |
end. | |
flush(Pid) -> | |
ok = gen_server:cast(Pid, flush). | |
% Producers call this when they're done (they will not queue anymore). | |
done(Pid) -> | |
case wait_previous_row_processed(Pid) of | |
{ok, MonRef} -> | |
receive | |
{'DOWN', MonRef, _, _, _} -> | |
ok | |
after 0 -> | |
erlang:demonitor(MonRef, [flush]), | |
ok = gen_server:cast(Pid, done) | |
end; | |
closed -> | |
ok | |
end. | |
init({NumProducers, _LessFun}) -> | |
{ok, PQueue} = merger:new(), | |
State = #state{ | |
num_producers = NumProducers, | |
rows = PQueue | |
%less_fun = fun({_, _, A}, {_, _, B}) -> LessFun(A, B) end | |
}, | |
{ok, State}. | |
handle_call(pop, From, #state{poped = []} = State) -> | |
#state{ | |
rows = Rows, | |
num_producers = N | |
} = State, | |
case merger:size(Rows) < N of | |
true -> | |
{noreply, State#state{consumer = From}}; | |
false -> | |
{ok, {_Key, {MinRow, Pid, Ref}}} = merger:out(Rows), | |
error_logger:error_msg("ABHI: Poped out ~p~n", [{Pid, Ref, MinRow}]), | |
{reply, {ok, MinRow}, State#state{rows = Rows, poped = [{Pid, Ref}]}} | |
end; | |
handle_call(pop_next, _From, #state{poped = [_ | _] = Poped} = State) -> | |
#state{rows = Rows, less_fun = _LessFun} = State, | |
case merger:size(Rows) of | |
0 -> | |
{reply, empty, State}; | |
_ -> | |
{ok, MinRow, {Pid, Ref}} = merger:out(Rows), | |
%{{Pid, Ref, MinRow}, Rows2} = merger:out(LessFun, Rows), | |
%NewState = State#state{rows = Rows2, poped = [{Pid, Ref} | Poped]}, | |
error_logger:error_msg("ABHI: pop_next row ~p~n", [{Pid, Ref, MinRow}]), | |
NewState = State#state{rows = Rows, poped = [{Pid, Ref} | Poped]}, | |
{reply, {ok, MinRow}, NewState} | |
end; | |
% Allowed to be called after the first pop in a merge iteration. | |
handle_call(peek, _From, #state{poped = [_ | _], rows = Rows} = State) -> | |
case merger:size(Rows) of | |
0 -> | |
{reply, empty, State}; | |
_ -> | |
{_, _, Row} = merger:min(Rows), | |
error_logger:error_msg("ABHI: peeked row: ~p~n", [Row]), | |
{reply, {ok, Row}, State} | |
end. | |
handle_cast({queue, Row, Pid, Ref}, #state{num_producers = N} = State) when N > 0 -> | |
#state{ | |
rows = Rows, | |
consumer = Consumer, | |
poped = Poped | |
} = State, | |
error_logger:error_msg("ABHI: ~p ~p ~p ~p Inserting: ~p Poped: ~p~n", | |
[?FILE, ?MODULE, ?LINE, ?MACHINE, {Row, Pid, Ref}, Poped]), | |
Key = parse_row(Row), | |
case Key of | |
{row_count, _Count} -> | |
error_logger:error_msg("ABHI: ~p ~p ~p ~p Consumer: ~p Row: ~p~n", | |
[?FILE, ?MODULE, ?LINE, ?MACHINE, Consumer, Row]), | |
gen_server:reply(Consumer, {ok, Row}), | |
Consumer2 = nil, | |
Poped2 = [{Pid, Ref} | Poped], | |
NewState = State#state{ | |
rows = Rows, | |
consumer = Consumer2, | |
poped = Poped2 | |
}, | |
{noreply, NewState}; | |
_ -> | |
error_logger:error_msg("ABHI: Key to be inserted: ~p~n", [Key]), | |
ok = merger:in(Rows, Key, {Row, Pid, Ref}), | |
error_logger:error_msg("ABHI: ~p ~p ~p~n", [?FILE, ?MODULE, ?LINE]), | |
case (Consumer =/= nil) andalso (merger:size(Rows) >= N) of | |
true -> | |
{ok, {_MinKey, {MinRow, Pid2, Ref2}}} = merger:out(Rows), | |
error_logger:error_msg("ABHI: ~p ~p ~p ~p Consumer: ~p MinRow: ~p NumProducers: ~p~n", | |
[?FILE, ?MODULE, ?LINE, ?MACHINE, Consumer, MinRow, N]), | |
gen_server:reply(Consumer, {ok, MinRow}), | |
Poped2 = [{Pid2, Ref2} | Poped], | |
Consumer2 = nil; | |
false -> | |
Poped2 = Poped, | |
Consumer2 = Consumer | |
end, | |
NewState = State#state{ | |
rows = Rows, | |
consumer = Consumer2, | |
poped = Poped2 | |
}, | |
{noreply, NewState} | |
end; | |
% Consumer should call this after doing its processing of the previously | |
% poped rows. | |
handle_cast(flush, #state{consumer = nil} = State) -> | |
#state{ | |
poped = Poped, | |
num_producers = N, | |
rows = Rows | |
} = State, | |
lists:foreach(fun({Pid, Ref}) -> Pid ! {ok, Ref} end, Poped), | |
case (N =:= 0) andalso (merger:size(Rows) =:= 0) of | |
true -> | |
{stop, normal, State#state{poped = []}}; | |
false -> | |
{noreply, State#state{poped = []}} | |
end; | |
handle_cast(done, #state{consumer = nil, num_producers = NumProds} = State) -> | |
NumProds2 = NumProds - 1, | |
case NumProds2 of | |
0 -> | |
case merger:size(State#state.rows) > 0 of | |
true -> | |
{noreply, State#state{num_producers = NumProds2}}; | |
false -> | |
{stop, normal, State#state{num_producers = NumProds2}} | |
end; | |
_ -> | |
{noreply, State#state{num_producers = NumProds2}} | |
end; | |
handle_cast(done, #state{poped = []} = State) -> | |
#state{ | |
rows = Rows, | |
num_producers = NumProds, | |
consumer = Consumer | |
} = State, | |
NumProds2 = NumProds - 1, | |
case NumProds2 of | |
0 -> | |
gen_server:reply(Consumer, closed), | |
{stop, normal, State}; | |
_ -> | |
error_logger:error_msg("ABHI: ~p ~p ~p Size: ~p NumProds2: ~p~n", | |
[?FILE, ?MODULE, ?LINE, merger:size(Rows), NumProds2]), | |
case merger:size(Rows) < NumProds2 of | |
true -> | |
{noreply, State#state{num_producers = NumProds2}}; | |
false -> | |
{ok, {_Key, {MinRow, Pid, Ref}}} = merger:out(Rows), | |
error_logger:error_msg("ABHI: ~p ~p ~p OutElem: ~p~n", | |
[?FILE, ?MODULE, ?LINE, MinRow]), | |
gen_server:reply(Consumer, {ok, MinRow}), | |
NewState = State#state{ | |
num_producers = NumProds2, | |
consumer = nil, | |
rows = Rows, | |
poped = [{Pid, Ref}] | |
}, | |
{noreply, NewState} | |
end | |
end. | |
handle_info(Msg, State) -> | |
{stop, {unexpected_msg, Msg}, State}. | |
terminate(_Reason, _State) -> | |
ok. | |
code_change(_OldVsn, State, _Extra) -> | |
{ok, State}. | |
wait_previous_row_processed(Pid) -> | |
MRef = erlang:monitor(process, Pid), | |
CurRef = erlang:erase(queue_ref), | |
case is_reference(CurRef) of | |
true -> | |
receive | |
{ok, CurRef} -> | |
{ok, MRef}; | |
{'DOWN', MRef, _, _, _} -> | |
closed | |
end; | |
false -> | |
{ok, MRef} | |
end. | |
parse_row(Row) -> | |
% error_logger:error_msg("ABHI: parse_row ~p~n", [Row]), | |
case Row of | |
{{{json, MRKey}, _DocID}, _JSONRow} -> | |
MRKey; | |
{row_count, _Count} -> | |
Row | |
end. |
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