pooler/test/fake_metrics.erl

%% @doc This stub module mimics part of folsom's API. It allows us to
%% test the metrics instrumentation of pooler without introducing a
%% dependency on folsom or another metrics application.
%%
-module(fake_metrics).
-behaviour(gen_server).
-define(SERVER, ?MODULE).

-include_lib("eunit/include/eunit.hrl").
%% ------------------------------------------------------------------
%% API Function Exports
%% ------------------------------------------------------------------

-export([
    start_link/0,
    notify/3,
    get_metrics/0,
    reset_metrics/0,
    stop/0
]).

%% ------------------------------------------------------------------
%% gen_server Function Exports
%% ------------------------------------------------------------------

-export([
    init/1,
    handle_call/3,
    handle_cast/2,
    handle_info/2,
    terminate/2,
    code_change/3
]).

%% ------------------------------------------------------------------
%% API Function Definitions
%% ------------------------------------------------------------------

start_link() ->
    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

notify(Name, Value, Type) ->
    gen_server:cast(?SERVER, {Name, Value, Type}).

reset_metrics() ->
    gen_server:call(?SERVER, reset).

stop() ->
    gen_server:call(?SERVER, stop).

get_metrics() ->
    gen_server:call(?SERVER, get_metrics).

%% ------------------------------------------------------------------
%% gen_server Function Definitions
%% ------------------------------------------------------------------
-record(state, {
    metrics = [] :: list()
}).

init(_) ->
    {ok, #state{}}.

handle_call(reset, _From, State) ->
    {reply, ok, State#state{metrics = []}};
handle_call(get_metrics, _From, #state{metrics = Metrics} = State) ->
    {reply, Metrics, State};
handle_call(stop, _From, State) ->
    {stop, normal, stop_ok, State};
handle_call(_Request, _From, State) ->
    erlang:error({what, _Request}),
    {noreply, ok, State}.

handle_cast({_N, _V, _T} = M, #state{metrics = Metrics} = State) ->
    {noreply, State#state{metrics = [M | Metrics]}};
handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.