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%%% Main worker for vmstats. This module sits in a loop fired off with
%%% timers with the main objective of routinely sending data to Sink.
-module(vmstats_server).
-behaviour(gen_server).
%% Interface
-export([start_link/2]).
%% Internal Exports
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
code_change/3, terminate/2]).
-define(TIMER_MSG, '#interval').
-record(state, {sink :: atom(),
key :: string(),
key_separator :: char() | iodata(),
sched_time :: enabled | disabled,
prev_sched :: [{integer(), integer(), integer()}],
timer_ref :: reference(),
interval :: integer(), % milliseconds
prev_io :: {In::integer(), Out::integer()},
prev_gc :: {GCs::integer(), Words::integer(), 0}}).
%%% INTERFACE
start_link(Sink, BaseKey) ->
gen_server:start_link({local, ?MODULE}, ?MODULE, {Sink, BaseKey}, []).
%%% INTERNAL EXPORTS
init({Sink, BaseKey}) ->
{ok, Interval} = application:get_env(vmstats, interval),
{ok, KeySeparator} = application:get_env(vmstats, key_separator),
{ok, SchedTimeEnabled} = application:get_env(vmstats, sched_time),
Ref = erlang:start_timer(Interval, self(), ?TIMER_MSG),
{{input, In}, {output, Out}} = erlang:statistics(io),
{GCs, Words, _} = erlang:statistics(garbage_collection),
State = #state{key = [BaseKey, KeySeparator],
key_separator = KeySeparator,
sink = Sink,
timer_ref = Ref,
interval = Interval,
prev_io = {In, Out},
prev_gc = {GCs, Words}},
erlang:system_flag(scheduler_wall_time, true),
case SchedTimeEnabled of
true ->
{ok, State#state{sched_time = enabled,
prev_sched = scheduler_wall_time()}};
false ->
{ok, State#state{sched_time = disabled}}
end.
handle_call(_Msg, _From, State) ->
{noreply, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info({timeout, R, ?TIMER_MSG}, S = #state{sink=Sink, key=K, key_separator=KS, interval=I, timer_ref=R}) ->
%% Processes
Sink:collect(gauge, [K,"proc_count"], erlang:system_info(process_count)),
Sink:collect(gauge, [K,"proc_limit"], erlang:system_info(process_limit)),
%% Messages in queues
TotalMessages = lists:foldl(
fun(Pid, Acc) ->
case process_info(Pid, message_queue_len) of
undefined -> Acc;
{message_queue_len, Count} -> Count+Acc
end
end,
0,
processes()
),
Sink:collect(gauge, [K,"messages_in_queues"], TotalMessages),
%% Modules loaded
Sink:collect(gauge, [K,"modules"], length(code:all_loaded())),
%% Queued up processes (lower is better)
Sink:collect(gauge, [K,"run_queue"], erlang:statistics(run_queue)),
%% Error logger backlog (lower is better)
{_, MQL} = process_info(whereis(error_logger), message_queue_len),
Sink:collect(gauge, [K,"error_logger_queue_len"], MQL),
collect_memory_stats(Sink, [K, "memory", KS]),
%% Incremental values
IO = collect_io_stats(Sink, [K, "io", KS], S),
GC = collect_gc_stats(Sink, [K, "gc", KS], S),
%% Reductions across the VM, excluding current time slice, already incremental
{_, Reds} = erlang:statistics(reductions),
Sink:collect(counter, [K,"reductions"], Reds),
SchedKey = [K, "scheduler_wall_time", KS],
Sched = collect_sched_time_stats(Sink, SchedKey, S),
Ref = erlang:start_timer(I, self(), ?TIMER_MSG),
{noreply, S#state{timer_ref = Ref,
prev_sched = Sched,
prev_io = IO, prev_gc = GC}};
handle_info(_Msg, {state, _Key, _TimerRef, _Delay}) ->
exit(forced_upgrade_restart);
handle_info(_Msg, {state, _Key, SchedTime, _PrevSched, _TimerRef, _Delay}) ->
%% The older version may have had the scheduler time enabled by default.
%% We could check for settings and preserve it in memory, but then it would
%% be more confusing if the behaviour changes on the next restart.
%% Instead, we show a warning and restart as usual.
case {application:get_env(vmstats, sched_time), SchedTime} of
{undefined, active} -> % default was on
error_logger:warning_msg("vmstats no longer runs scheduler time by default. Restarting...");
_ ->
ok
end,
exit(forced_upgrade_restart);
handle_info(_Msg, State) ->
{noreply, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
terminate(_Reason, _State) ->
ok.
%% Returns the two timeslices as a ratio of each other,
%% as a percentage so that StatsD gets to print something > 1
wall_time_diff(T1, T2) ->
[{I, Active2-Active1, Total2-Total1}
|| {{I, Active1, Total1}, {I, Active2, Total2}} <- lists:zip(T1,T2)].
collect_io_stats(Sink, Key, #state{prev_io = {PrevIn, PrevOut}}) ->
{{input, In}, {output, Out}} = erlang:statistics(io),
Sink:collect(counter, [Key, "bytes_in"], In - PrevIn),
Sink:collect(counter, [Key, "bytes_out"], Out - PrevOut),
{In, Out}.
collect_gc_stats(Sink, Key, #state{prev_gc = {PrevGCs, PrevWords}}) ->
{GCs, Words, _} = erlang:statistics(garbage_collection),
Sink:collect(counter, [Key, "count"], GCs - PrevGCs),
Sink:collect(counter, [Key, "words_reclaimed"], Words - PrevWords),
{GCs, Words}.
%% There are more options available, but not all were kept.
%% Memory usage is in bytes.
collect_memory_stats(Sink, Key) ->
Sink:collect(gauge, [Key, "total"], erlang:memory(total)),
Sink:collect(gauge, [Key, "procs_used"], erlang:memory(processes_used)),
Sink:collect(gauge, [Key, "atom_used"], erlang:memory(atom_used)),
Sink:collect(gauge, [Key, "binary"], erlang:memory(binary)),
Sink:collect(gauge, [Key, "ets"], erlang:memory(ets)).
collect_sched_time_stats(Sink, Key, #state{sched_time = enabled, prev_sched = PrevSched, key_separator = KS}) ->
Sched = scheduler_wall_time(),
[begin
LSid = integer_to_list(Sid),
Sink:collect(timing, [Key, LSid, KS, "active"], Active),
Sink:collect(timing, [Key, LSid, KS, "total"], Total)
end
|| {Sid, Active, Total} <- wall_time_diff(PrevSched, Sched)],
Sched;
collect_sched_time_stats(_Sink, _Key, #state{prev_sched = PrevSched}) -> PrevSched.
scheduler_wall_time() ->
lists:sort(erlang:statistics(scheduler_wall_time)).
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