tonysun83 commented on a change in pull request #470: Scheduling Replicator URL: https://github.com/apache/couchdb/pull/470#discussion_r110554109
########## File path: src/couch_replicator/src/couch_replicator_connection.erl ########## @@ -0,0 +1,241 @@ +% 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_replicator_connection). + +-behavior(gen_server). + +-behavior(config_listener). + + +-export([ + start_link/0 +]). + +-export([ + init/1, + terminate/2, + handle_call/3, + handle_info/2, + handle_cast/2, + code_change/3 +]). + +-export([ + acquire/1, + release/1 +]). + +-export([ + handle_config_change/5, + handle_config_terminate/3 +]). + + +-include_lib("ibrowse/include/ibrowse.hrl"). + + +-define(DEFAULT_CLOSE_INTERVAL, 90000). +-define(RELISTEN_DELAY, 5000). + + +-record(state, { + close_interval, + timer +}). + +-record(connection, { + worker, + host, + port, + mref +}). + + +start_link() -> + gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). + + +init([]) -> + process_flag(trap_exit, true), + ?MODULE = ets:new(?MODULE, [named_table, public, + {keypos, #connection.worker}]), + ok = config:listen_for_changes(?MODULE, nil), + Interval = config:get_integer("replicator", "connection_close_interval", + ?DEFAULT_CLOSE_INTERVAL), + {ok, Timer} = timer:send_after(Interval, close_idle_connections), + ibrowse:add_config([{inactivity_timeout, Interval}]), + {ok, #state{close_interval=Interval, timer=Timer}}. + + +acquire(URL) when is_binary(URL) -> + acquire(binary_to_list(URL)); + +acquire(URL0) -> + URL = couch_util:url_strip_password(URL0), + case gen_server:call(?MODULE, {acquire, URL}) of + {ok, Worker} -> + link(Worker), + {ok, Worker}; + {error, all_allocated} -> + {ok, Pid} = ibrowse:spawn_link_worker_process(URL), + ok = gen_server:call(?MODULE, {create, URL, Pid}), + {ok, Pid}; + {error, Reason} -> + {error, Reason} + end. + + +release(Worker) -> + unlink(Worker), + gen_server:cast(?MODULE, {release, Worker}). + + +handle_call({acquire, URL}, From, State) -> + {Pid, _Ref} = From, + case ibrowse_lib:parse_url(URL) of + #url{host=Host, port=Port} -> + Pat = #connection{host=Host, port=Port, mref=undefined, _='_'}, + case ets:match_object(?MODULE, Pat, 1) of + '$end_of_table' -> + {reply, {error, all_allocated}, State}; + {[Worker], _Cont} -> + couch_stats:increment_counter([couch_replicator, connection, + acquires]), + ets:insert(?MODULE, Worker#connection{mref=monitor(process, + Pid)}), + {reply, {ok, Worker#connection.worker}, State} + end; + {error, invalid_uri} -> + {reply, {error, invalid_uri}, State} + end; + +handle_call({create, URL, Worker}, From, State) -> + {Pid, _Ref} = From, + case ibrowse_lib:parse_url(URL) of + #url{host=Host, port=Port} -> + link(Worker), + couch_stats:increment_counter([couch_replicator, connection, + creates]), + true = ets:insert_new( + ?MODULE, + #connection{host=Host, port=Port, worker=Worker, + mref=monitor(process, Pid)} + ), + {reply, ok, State} + end. + + +handle_cast({release, WorkerPid}, State) -> + couch_stats:increment_counter([couch_replicator, connection, releasees]), + case ets:lookup(?MODULE, WorkerPid) of + [Worker] -> + case Worker#connection.mref of + MRef when is_reference(MRef) -> demonitor(MRef, [flush]); + undefined -> ok + end, + ets:insert(?MODULE, Worker#connection{mref=undefined}); + [] -> + ok + end, + {noreply, State}; + +handle_cast({connection_close_interval, V}, State) -> + {ok, cancel} = timer:cancel(State#state.timer), + {ok, NewTimer} = timer:send_after(V, close_idle_connections), + ibrowse:add_config([{inactivity_timeout, V}]), + {noreply, State#state{close_interval=V, timer=NewTimer}}. + + +% owner crashed +handle_info({'DOWN', Ref, process, _Pid, _Reason}, State) -> + couch_stats:increment_counter([couch_replicator, connection, + owner_crashes]), + ets:match_delete(?MODULE, #connection{mref=Ref, _='_'}), + {noreply, State}; + +% worker crashed +handle_info({'EXIT', Pid, Reason}, State) -> + couch_stats:increment_counter([couch_replicator, connection, + worker_crashes]), + case ets:lookup(?MODULE, Pid) of + [] -> + ok; + [Worker] -> + #connection{host=Host, port=Port} = Worker, + maybe_log_worker_death(Host, Port, Reason), + case Worker#connection.mref of + MRef when is_reference(MRef) -> demonitor(MRef, [flush]); + undefined -> ok + end, + ets:delete(?MODULE, Pid) + end, + {noreply, State}; + +handle_info(close_idle_connections, State) -> + #state{ + close_interval=Interval, + timer=Timer + } = State, + Conns = ets:match_object(?MODULE, #connection{mref=undefined, _='_'}), + lists:foreach(fun(Conn) -> + couch_stats:increment_counter([couch_replicator, connection, closes]), + delete_worker(Conn) + end, Conns), + {ok, cancel} = timer:cancel(Timer), + {ok, NewTimer} = timer:send_after(Interval, close_idle_connections), + {noreply, State#state{timer=NewTimer}}; + +handle_info(restart_config_listener, State) -> + ok = config:listen_for_changes(?MODULE, nil), + {noreply, State}. + + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + + +terminate(_Reason, _State) -> + ok. + + +maybe_log_worker_death(_Host, _Port, normal) -> + ok; + +maybe_log_worker_death(Host, Port, Reason) -> + ErrMsg = "Replication connection to: ~p:~p died with reason ~p", + couch_log:info(ErrMsg, [Host, Port, Reason]). + + +-spec delete_worker(#connection{}) -> ok. +delete_worker(Worker) -> + ets:delete(?MODULE, Worker#connection.worker), + unlink(Worker#connection.worker), + spawn(fun() -> ibrowse_http_client:stop(Worker#connection.worker) end), Review comment: IIUC, every Interval seconds, we go through a sweep through the ETS table and find worker processes which don't have a monitor reference for deletion. Is there ever a situation where lingering worker processes/connections aren't closed? I do see that that stop/1 does have a timeout, so if it's issued a stop, at some point the timeout will trigger and we'll kill it. If this ```couch_replicator_connection``` process crashes/restarts, would those worker processes stick around until some other time out? Just brainstorming here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
