nickva commented on a change in pull request #470: Scheduling Replicator URL: https://github.com/apache/couchdb/pull/470#discussion_r110556528
########## 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: Good observation. Yeah they are not closed immediately because then there is not chance fo reuse and the connection pool won't serve its purpose. So connections stay around after they are used for some time ready to be picked up by some other owner and they need to stick around. However, we don't want them to stick around forever either, otherwise the pool will just keep growing. So we sweep through and close the idle connection. Now ibrowse clients actually have a close on idle timeout as well (I think 90 sec or so). If we I think this is a case of us not trusting that mechanism 100% and implementing our own cleanup. ---------------------------------------------------------------- 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
