Add 'src/ioq/' from commit 'e641a740978447f0b29785580e46d2e30e822001'
git-subtree-dir: src/ioq
git-subtree-mainline: c8a5757c33c8f782d935fce2f804cb745bf77b4a
git-subtree-split: e641a740978447f0b29785580e46d2e30e822001
diff --git a/src/ioq/.gitignore b/src/ioq/.gitignore
new file mode 100644
index 0000000..21cf3d3
--- /dev/null
+++ b/src/ioq/.gitignore
@@ -0,0 +1,2 @@
+.rebar
+ebin/
diff --git a/src/ioq/src/ioq.app.src b/src/ioq/src/ioq.app.src
new file mode 100644
index 0000000..65ea50d
--- /dev/null
+++ b/src/ioq/src/ioq.app.src
@@ -0,0 +1,21 @@
+% 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.
+
+{application,ioq, [
+ {description, "I/O prioritizing engine"},
+ {vsn, git},
+ {registered,[]},
+ {applications,[kernel,stdlib,config]},
+ {mod,{ioq_app,[]}},
+ {env, []},
+ {modules,[ioq,ioq_app,ioq_sup]}
+]}.
diff --git a/src/ioq/src/ioq.erl b/src/ioq/src/ioq.erl
new file mode 100644
index 0000000..81d94a3
--- /dev/null
+++ b/src/ioq/src/ioq.erl
@@ -0,0 +1,189 @@
+% 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(ioq).
+-behaviour(gen_server).
+-behaviour(config_listener).
+
+-export([start_link/0, call/3]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2, code_change/3, terminate/2]).
+
+% config_listener api
+-export([handle_config_change/5, handle_config_terminate/3]).
+
+-define(RELISTEN_DELAY, 5000).
+
+-record(state, {
+ concurrency,
+ ratio,
+ interactive=queue:new(),
+ background=queue:new(),
+ running=[]
+}).
+
+-record(request, {
+ fd,
+ msg,
+ priority,
+ from,
+ ref
+}).
+
+start_link() ->
+ gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+call(Fd, Msg, Metadata) ->
+ Priority = io_class(Msg, Metadata),
+ case bypass(Priority) of
+ true ->
+ gen_server:call(Fd, Msg);
+ false ->
+ queued_call(Fd, Msg, Priority)
+ end.
+
+bypass(Priority) ->
+ config:get("ioq.bypass", atom_to_list(Priority)) =:= "true".
+
+io_class({prompt, _}, _) ->
+ os_process;
+io_class({data, _}, _) ->
+ os_process;
+io_class(_, {interactive, _}) ->
+ read;
+io_class(_, {db_update, _}) ->
+ write;
+io_class(_, {view_update, _, _}) ->
+ view_update;
+io_class(_, {internal_repl, _}) ->
+ shard_sync;
+io_class(_, {db_compact, _}) ->
+ compaction;
+io_class(_, {view_compact, _, _}) ->
+ compaction;
+io_class(_, _) ->
+ other.
+
+queued_call(Fd, Msg, Priority) ->
+ Request = #request{fd=Fd, msg=Msg, priority=Priority, from=self()},
+ try
+ gen_server:call(?MODULE, Request, infinity)
+ catch
+ exit:{noproc,_} ->
+ gen_server:call(Fd, Msg, infinity)
+ end.
+
+init(_) ->
+ ok = config:listen_for_changes(?MODULE, nil),
+ State = #state{},
+ {ok, read_config(State)}.
+
+read_config(State) ->
+ Ratio = list_to_float(config:get("ioq", "ratio", "0.01")),
+ Concurrency = list_to_integer(config:get("ioq", "concurrency", "10")),
+ State#state{concurrency=Concurrency, ratio=Ratio}.
+
+handle_call(#request{}=Request, From, State) ->
+ {noreply, enqueue_request(Request#request{from=From}, State), 0}.
+
+handle_cast(change, State) ->
+ {noreply, read_config(State)};
+handle_cast(_Msg, State) ->
+ {noreply, State}.
+
+handle_info({Ref, Reply}, State) ->
+ case lists:keytake(Ref, #request.ref, State#state.running) of
+ {value, Request, Remaining} ->
+ erlang:demonitor(Ref, [flush]),
+ gen_server:reply(Request#request.from, Reply),
+ {noreply, State#state{running=Remaining}, 0};
+ false ->
+ {noreply, State, 0}
+ end;
+handle_info({'DOWN', Ref, _, _, Reason}, State) ->
+ case lists:keytake(Ref, #request.ref, State#state.running) of
+ {value, Request, Remaining} ->
+ gen_server:reply(Request#request.from, {'EXIT', Reason}),
+ {noreply, State#state{running=Remaining}, 0};
+ false ->
+ {noreply, State, 0}
+ end;
+handle_info(restart_config_listener, State) ->
+ ok = config:listen_for_changes(?MODULE, nil),
+ {noreply, State};
+handle_info(timeout, State) ->
+ {noreply, maybe_submit_request(State)}.
+
+handle_config_change("ioq", _, _, _, _) ->
+ {ok, gen_server:cast(?MODULE, change)};
+handle_config_change(_, _, _, _, _) ->
+ {ok, nil}.
+
+handle_config_terminate(_Server, stop, _State) ->
+ ok;
+handle_config_terminate(_Server, _Reason, _State) ->
+ erlang:send_after(?RELISTEN_DELAY, whereis(?MODULE), restart_config_listener).
+
+code_change(_Vsn, State, _Extra) ->
+ {ok, State}.
+
+terminate(_Reason, _State) ->
+ ok.
+
+enqueue_request(#request{priority=compaction}=Request, #state{}=State) ->
+ State#state{background=queue:in(Request, State#state.background)};
+enqueue_request(#request{priority=shard_sync}=Request, #state{}=State) ->
+ State#state{background=queue:in(Request, State#state.background)};
+enqueue_request(#request{}=Request, #state{}=State) ->
+ State#state{interactive=queue:in(Request, State#state.interactive)}.
+
+maybe_submit_request(#state{concurrency=Concurrency, running=Running}=State)
+ when length(Running) < Concurrency ->
+ case make_next_request(State) of
+ State ->
+ State;
+ NewState when length(Running) >= Concurrency - 1 ->
+ NewState;
+ NewState ->
+ maybe_submit_request(NewState)
+ end;
+maybe_submit_request(State) ->
+ State.
+
+make_next_request(#state{}=State) ->
+ case {queue:is_empty(State#state.background), queue:is_empty(State#state.interactive)} of
+ {true, true} ->
+ State;
+ {true, false} ->
+ choose_next_request(#state.interactive, State);
+ {false, true} ->
+ choose_next_request(#state.background, State);
+ {false, false} ->
+ case couch_rand:uniform() < State#state.ratio of
+ true ->
+ choose_next_request(#state.background, State);
+ false ->
+ choose_next_request(#state.interactive, State)
+ end
+ end.
+
+choose_next_request(Index, State) ->
+ case queue:out(element(Index, State)) of
+ {empty, _} ->
+ State;
+ {{value, Request}, Q} ->
+ submit_request(Request, setelement(Index, State, Q))
+ end.
+
+submit_request(#request{}=Request, #state{}=State) ->
+ Ref = erlang:monitor(process, Request#request.fd),
+ Request#request.fd ! {'$gen_call', {self(), Ref}, Request#request.msg},
+ State#state{running = [Request#request{ref=Ref} | State#state.running]}.
diff --git a/src/ioq/src/ioq_app.erl b/src/ioq/src/ioq_app.erl
new file mode 100644
index 0000000..2e6d75a
--- /dev/null
+++ b/src/ioq/src/ioq_app.erl
@@ -0,0 +1,21 @@
+% 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(ioq_app).
+-behaviour(application).
+-export([start/2, stop/1]).
+
+start(_StartType, _StartArgs) ->
+ ioq_sup:start_link().
+
+stop(_State) ->
+ ok.
diff --git a/src/ioq/src/ioq_sup.erl b/src/ioq/src/ioq_sup.erl
new file mode 100644
index 0000000..c4d04a9
--- /dev/null
+++ b/src/ioq/src/ioq_sup.erl
@@ -0,0 +1,24 @@
+% 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(ioq_sup).
+-behaviour(supervisor).
+-export([start_link/0, init/1]).
+
+%% Helper macro for declaring children of supervisor
+-define(CHILD(I, Type), {I, {I, start_link, []}, permanent, 5000, Type, [I]}).
+
+start_link() ->
+ supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+init([]) ->
+ {ok, { {one_for_one, 5, 10}, [?CHILD(ioq, worker)]}}.
