pooler/test/pooler_tests.erl

-module(pooler_tests).

-include_lib("eunit/include/eunit.hrl").

-export([sleep_for_configured_timeout/0]).

% The `user' processes represent users of the pooler library.  A user
% process will take a pid, report details on the pid it has, release
% and take a new pid, stop cleanly, and crash.

start_user() ->
    spawn(fun() -> user_loop(start) end).

user_id(Pid) ->
    Pid ! {get_tc_id, self()},
    receive
        {Type, Id} ->
            {Type, Id}
    end.

user_new_tc(Pid) ->
    Pid ! new_tc.

user_stop(Pid) ->
    Pid ! stop.

user_crash(Pid) ->
    Pid ! crash.

user_loop(Atom) when Atom =:= error_no_members orelse Atom =:= start ->
    user_loop(pooler:take_member(test_pool_1));
user_loop(MyTC) ->
    receive
        {get_tc_id, From} ->
            From ! pooled_gs:get_id(MyTC),
            user_loop(MyTC);
        {ping_tc, From} ->
            From ! pooled_gs:ping(MyTC),
            user_loop(MyTC);
        {ping_count, From} ->
            From ! pooled_gs:ping_count(MyTC),
            user_loop(MyTC);
        new_tc ->
            pooler:return_member(test_pool_1, MyTC, ok),
            MyNewTC = pooler:take_member(test_pool_1),
            user_loop(MyNewTC);
        stop ->
            pooler:return_member(test_pool_1, MyTC, ok),
            stopped;
        crash ->
            erlang:error({user_loop, kaboom})
    end.

% The `tc' processes represent the pids tracked by pooler for testing.
% They have a type and an ID and can report their type and ID and
% stop.

%% tc_loop({Type, Id}) ->
%%     receive
%%         {get_id, From} ->
%%             From ! {ok, Type, Id},
%%             tc_loop({Type, Id});
%%         stop -> stopped;
%%         crash ->
%%             erlang:error({tc_loop, kaboom})
%%     end.

%% get_tc_id(Pid) ->
%%     Pid ! {get_id, self()},
%%     receive
%%         {ok, Type, Id} ->
%%             {Type, Id}
%%     after 200 ->
%%             timeout
%%     end.

%% stop_tc(Pid) ->
%%     Pid ! stop.

%% tc_starter(Type) ->
%%     Ref = make_ref(),
%%     spawn_link(fun() -> tc_loop({Type, Ref}) end).

%% assert_tc_valid(Pid) ->
%%     ?assertMatch({_Type, _Ref}, get_tc_id(Pid)),
%%     ok.

% tc_sanity_test() ->
%     Pid1 = tc_starter("1"),
%     {"1", Id1} = get_tc_id(Pid1),
%     Pid2 = tc_starter("1"),
%     {"1", Id2} = get_tc_id(Pid2),
%     ?assertNot(Id1 == Id2),
%     stop_tc(Pid1),
%     stop_tc(Pid2).

% user_sanity_test() ->
%     Pid1 = tc_starter("1"),
%     User = spawn(fun() -> user_loop(Pid1) end),
%     ?assertMatch({"1", _Ref}, user_id(User)),
%     user_crash(User),
%     stop_tc(Pid1).

pooler_basics_via_config_test_() ->
    {setup,
        fun() ->
            {ok, _} = error_logger_mon:start_link(),
            error_logger_mon:install_handler(pooler),
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            error_logger_mon:uninstall_handler(),
            ok = error_logger_mon:stop(),
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                error_logger_mon:reset(),
                Pools = [
                    #{
                        name => test_pool_1,
                        max_count => 3,
                        init_count => 2,
                        cull_interval => {0, min},
                        start_mfa => {pooled_gs, start_link, [{"type-0"}]}
                    }
                ],
                application:set_env(pooler, pools, Pools),
                application:start(pooler)
            end,
            fun(_X) ->
                application:stop(pooler)
            end,
            basic_tests()}}.

pooler_basics_dynamic_test_() ->
    {setup,
        fun() ->
            {ok, _} = error_logger_mon:start_link(),
            error_logger_mon:install_handler(pooler),
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            error_logger_mon:uninstall_handler(),
            ok = error_logger_mon:stop(),
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                error_logger_mon:reset(),
                Pool = #{
                    name => test_pool_1,
                    max_count => 3,
                    init_count => 2,
                    start_mfa => {pooled_gs, start_link, [{"type-0"}]}
                },
                application:unset_env(pooler, pools),
                application:start(pooler),
                pooler:new_pool(Pool)
            end,
            fun(_X) ->
                application:stop(pooler)
            end,
            basic_tests()}}.

pooler_basics_integration_to_other_supervisor_test_() ->
    {setup,
        fun() ->
            {ok, _} = error_logger_mon:start_link(),
            error_logger_mon:install_handler(pooler),
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            error_logger_mon:uninstall_handler(),
            ok = error_logger_mon:stop(),
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                error_logger_mon:reset(),
                Pool = #{
                    name => test_pool_1,
                    max_count => 3,
                    init_count => 2,
                    start_mfa => {pooled_gs, start_link, [{"type-0"}]}
                },
                application:unset_env(pooler, pools),
                application:start(pooler),
                supervisor:start_link(fake_external_supervisor, Pool)
            end,
            fun({ok, SupPid}) ->
                exit(SupPid, normal),
                application:stop(pooler)
            end,
            basic_tests()}}.

basic_tests() ->
    [
        {"there are init_count members at start", fun() ->
            Stats = [P || {P, {_, free, _}} <- pooler:pool_stats(test_pool_1)],
            ?assertEqual(2, length(Stats))
        end},

        {"take and return one", fun() ->
            P = pooler:take_member(test_pool_1),
            ?assertMatch({"type-0", _Id}, pooled_gs:get_id(P)),
            ok = pooler:return_member(test_pool_1, P, ok)
        end},

        {"take and return one, named pool", fun() ->
            P = pooler:take_member(test_pool_1),
            ?assertMatch({"type-0", _Id}, pooled_gs:get_id(P)),
            ok,
            pooler:return_member(test_pool_1, P)
        end},

        {"attempt to take form unknown pool", fun() ->
            %% since pools are now servers, an unknown pool will timeout
            ?assertExit({noproc, _}, pooler:take_member(bad_pool_name))
        end},

        {"members creation is triggered after pool exhaustion until max", fun() ->
            %% init count is 2
            Pids0 = [pooler:take_member(test_pool_1), pooler:take_member(test_pool_1)],
            %% since new member creation is async, can only assert
            %% that we will get a pid, but may not be first try.
            Pids = get_n_pids(1, Pids0),
            %% pool is at max now, requests should give error
            ?assertEqual(error_no_members, pooler:take_member(test_pool_1)),
            ?assertEqual(error_no_members, pooler:take_member(test_pool_1)),
            PRefs = [R || {_T, R} <- [pooled_gs:get_id(P) || P <- Pids]],
            % no duplicates
            ?assertEqual(length(PRefs), length(lists:usort(PRefs)))
        end},

        {"pids are reused most recent return first", fun() ->
            P1 = pooler:take_member(test_pool_1),
            P2 = pooler:take_member(test_pool_1),
            ?assertNot(P1 == P2),
            ok = pooler:return_member(test_pool_1, P1, ok),
            ok = pooler:return_member(test_pool_1, P2, ok),
            % pids are reused most recent first
            ?assertEqual(P2, pooler:take_member(test_pool_1)),
            ?assertEqual(P1, pooler:take_member(test_pool_1))
        end},

        {"if an in-use pid crashes it is replaced", fun() ->
            Pids0 = get_n_pids(3, []),
            Ids0 = [pooled_gs:get_id(P) || P <- Pids0],
            % crash them all
            [pooled_gs:crash(P) || P <- Pids0],
            Pids1 = get_n_pids(3, []),
            Ids1 = [pooled_gs:get_id(P) || P <- Pids1],
            [?assertNot(lists:member(I, Ids0)) || I <- Ids1]
        end},

        {"if a free pid crashes it is replaced", fun() ->
            FreePids = [P || {P, {_, free, _}} <- pooler:pool_stats(test_pool_1)],
            [exit(P, kill) || P <- FreePids],
            Pids1 = get_n_pids(3, []),
            ?assertEqual(3, length(Pids1))
        end},

        {"if a pid is returned with bad status it is replaced", fun() ->
            Pids0 = get_n_pids(3, []),
            Ids0 = [pooled_gs:get_id(P) || P <- Pids0],
            % return them all marking as bad
            [pooler:return_member(test_pool_1, P, fail) || P <- Pids0],
            Pids1 = get_n_pids(3, []),
            Ids1 = [pooled_gs:get_id(P) || P <- Pids1],
            [?assertNot(lists:member(I, Ids0)) || I <- Ids1]
        end},

        {"if a consumer crashes, pid is replaced", fun() ->
            Consumer = start_user(),
            StartId = user_id(Consumer),
            user_crash(Consumer),
            NewPid = hd(get_n_pids(1, [])),
            NewId = pooled_gs:get_id(NewPid),
            ?assertNot(NewId == StartId)
        end},

        {"it is ok to return an unknown pid", fun() ->
            Bogus1 = spawn(fun() -> ok end),
            Bogus2 = spawn(fun() -> ok end),
            ?assertEqual(ok, pooler:return_member(test_pool_1, Bogus1, ok)),
            ?assertEqual(ok, pooler:return_member(test_pool_1, Bogus2, fail))
        end},

        {"it is ok to return a pid more than once", fun() ->
            M = pooler:take_member(test_pool_1),
            [
                pooler:return_member(test_pool_1, M)
             || _I <- lists:seq(1, 37)
            ],
            ?assertEqual(
                36,
                length(
                    lists:filter(
                        fun
                            (
                                #{
                                    msg :=
                                        {report, #{
                                            label := "ignored return of free member",
                                            pid := Pid
                                        }}
                                }
                            ) ->
                                Pid =:= M;
                            (_) ->
                                false
                        end,
                        error_logger_mon:get_msgs()
                    )
                )
            ),
            M1 = pooler:take_member(test_pool_1),
            M2 = pooler:take_member(test_pool_1),
            ?assert(M1 =/= M2),
            Pool1 = gen_server:call(test_pool_1, dump_pool),
            ?assertEqual(2, maps:get(in_use_count, Pool1)),
            ?assertEqual(0, maps:get(free_count, Pool1)),
            pooler:return_member(test_pool_1, M1),
            pooler:return_member(test_pool_1, M2),
            Pool2 = gen_server:call(test_pool_1, dump_pool),
            ?assertEqual(0, maps:get(in_use_count, Pool2)),
            ?assertEqual(2, maps:get(free_count, Pool2)),
            ok
        end},

        {"calling return_member on error_no_members is ignored", fun() ->
            ?assertEqual(ok, pooler:return_member(test_pool_1, error_no_members)),
            ?assertEqual(ok, pooler:return_member(test_pool_1, error_no_members, ok)),
            ?assertEqual(ok, pooler:return_member(test_pool_1, error_no_members, fail))
        end},

        {"dynamic pool creation", fun() ->
            PoolSpec = [
                {name, dyn_pool_1},
                {max_count, 3},
                {init_count, 2},
                {start_mfa, {pooled_gs, start_link, [{"dyn-0"}]}}
            ],
            {ok, SupPid1} = pooler:new_pool(PoolSpec),
            ?assert(is_pid(SupPid1)),
            M = pooler:take_member(dyn_pool_1),
            ?assertMatch({"dyn-0", _Id}, pooled_gs:get_id(M)),
            ?assertEqual(ok, pooler:rm_pool(dyn_pool_1)),
            ?assertExit({noproc, _}, pooler:take_member(dyn_pool_1)),
            %% verify pool of same name can be created after removal
            {ok, SupPid2} = pooler:new_pool(PoolSpec),
            ?assert(is_pid(SupPid2)),
            %% remove non-existing pool
            ?assertEqual(ok, pooler:rm_pool(dyn_pool_X)),
            ?assertEqual(ok, pooler:rm_pool(dyn_pool_1))
        end},

        {"metrics have been called (no timeout/queue)", fun() ->
            %% exercise the API to ensure we have certain keys reported as metrics
            fake_metrics:reset_metrics(),
            Pids = [pooler:take_member(test_pool_1) || _I <- lists:seq(1, 10)],
            [pooler:return_member(test_pool_1, P) || P <- Pids],
            catch pooler:take_member(bad_pool_name),
            %% kill and unused member
            exit(hd(Pids), kill),
            %% kill a used member
            KillMe = pooler:take_member(test_pool_1),
            exit(KillMe, kill),
            %% FIXME: We need to wait for pooler to process the
            %% exit message. This is ugly, will fix later.

            % :(
            timer:sleep(200),
            ExpectKeys = lists:sort([
                <<"pooler.test_pool_1.error_no_members_count">>,
                <<"pooler.test_pool_1.events">>,
                <<"pooler.test_pool_1.free_count">>,
                <<"pooler.test_pool_1.in_use_count">>,
                <<"pooler.test_pool_1.killed_free_count">>,
                <<"pooler.test_pool_1.killed_in_use_count">>,
                <<"pooler.test_pool_1.take_rate">>
            ]),
            Metrics = fake_metrics:get_metrics(),
            GotKeys = lists:usort([Name || {Name, _, _} <- Metrics]),
            ?assertEqual(ExpectKeys, GotKeys)
        end},

        {"metrics have been called (with timeout/queue)", fun() ->
            %% exercise the API to ensure we have certain keys reported as metrics
            fake_metrics:reset_metrics(),
            %% pass a non-zero timeout here to exercise queueing
            Pids = [pooler:take_member(test_pool_1, 1) || _I <- lists:seq(1, 10)],
            [pooler:return_member(test_pool_1, P) || P <- Pids],
            catch pooler:take_member(bad_pool_name),
            %% kill and unused member
            exit(hd(Pids), kill),
            %% kill a used member
            KillMe = pooler:take_member(test_pool_1),
            exit(KillMe, kill),
            %% FIXME: We need to wait for pooler to process the
            %% exit message. This is ugly, will fix later.

            % :(
            timer:sleep(200),
            ExpectKeys = lists:sort([
                <<"pooler.test_pool_1.error_no_members_count">>,
                <<"pooler.test_pool_1.events">>,
                <<"pooler.test_pool_1.free_count">>,
                <<"pooler.test_pool_1.in_use_count">>,
                <<"pooler.test_pool_1.killed_free_count">>,
                <<"pooler.test_pool_1.killed_in_use_count">>,
                <<"pooler.test_pool_1.take_rate">>,
                <<"pooler.test_pool_1.queue_count">>
            ]),
            Metrics = fake_metrics:get_metrics(),
            GotKeys = lists:usort([Name || {Name, _, _} <- Metrics]),
            ?assertEqual(ExpectKeys, GotKeys)
        end},

        {"accept bad member is handled", fun() ->
            Bad = spawn(fun() -> ok end),
            FakeStarter = spawn(fun() -> starter end),
            ?assertEqual(ok, pooler:accept_member(test_pool_1, {FakeStarter, Bad}))
        end},

        {"utilization returns sane results", fun() ->
            #{max_count := MaxCount, queue_max := QueueMax} = dump_pool(test_pool_1),

            ?assertEqual(MaxCount, proplists:get_value(max_count, pooler:pool_utilization(test_pool_1))),
            ?assertEqual(0, proplists:get_value(in_use_count, pooler:pool_utilization(test_pool_1))),
            ?assertEqual(2, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1))),
            ?assertEqual(0, proplists:get_value(queued_count, pooler:pool_utilization(test_pool_1))),
            ?assertEqual(QueueMax, proplists:get_value(queue_max, pooler:pool_utilization(test_pool_1)))
        end}
    ].

pooler_groups_test_() ->
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                Pools = [
                    [
                        {name, test_pool_1},
                        {group, group_1},
                        {max_count, 3},
                        {init_count, 2},
                        {start_mfa, {pooled_gs, start_link, [{"type-1-1"}]}}
                    ],
                    [
                        {name, test_pool_2},
                        {group, group_1},
                        {max_count, 3},
                        {init_count, 2},
                        {start_mfa, {pooled_gs, start_link, [{"type-1-2"}]}}
                    ],
                    %% test_pool_3 not part of the group
                    [
                        {name, test_pool_3},
                        {group, undefined},
                        {max_count, 3},
                        {init_count, 2},
                        {start_mfa, {pooled_gs, start_link, [{"type-3"}]}}
                    ]
                ],
                application:set_env(pooler, pools, Pools),
                pg_start(),
                application:start(pooler)
            end,
            fun(_X) ->
                application:stop(pooler),
                pg_stop()
            end,
            [
                {"take and return one group member (repeated)", fun() ->
                    Types = [
                        begin
                            Pid = pooler:take_group_member(group_1),
                            ?assert(is_pid(Pid), [{result, Pid}, {i, I}]),
                            {Type, _} = pooled_gs:get_id(Pid),
                            ?assertMatch("type-1" ++ _, Type),
                            ok = pooler:return_group_member(group_1, Pid, ok),
                            timer:sleep(10),
                            Type
                        end
                     || I <- lists:seq(1, 50)
                    ],
                    Type_1_1 = [X || "type-1-1" = X <- Types],
                    Type_1_2 = [X || "type-1-2" = X <- Types],
                    ?assert(length(Type_1_1) > 0, [{types, Types}]),
                    ?assert(length(Type_1_2) > 0, [{types, Types}])
                end},

                {"take member from unknown group", fun() ->
                    ?assertEqual(
                        error_no_members,
                        pooler:take_group_member(not_a_group)
                    )
                end},

                {"return member to unknown group", fun() ->
                    Pid = pooler:take_group_member(group_1),
                    ?assertEqual(ok, pooler:return_group_member(no_such_group, Pid))
                end},

                {"return member to wrong group", fun() ->
                    Pid = pooler:take_member(test_pool_3),
                    ?assertEqual(ok, pooler:return_group_member(group_1, Pid))
                end},

                {"return member with something which is not a pid", fun() ->
                    ?assertException(error, _, pooler:return_group_member(group_1, not_pid))
                end},

                {"take member from empty group", fun() ->
                    %% artificially empty group member list
                    [pg_leave(group_1, M) || M <- pooler:group_pools(group_1)],
                    ?assertEqual(error_no_members, pooler:take_group_member(group_1))
                end},

                {"return member to group, implied ok", fun() ->
                    Pid = pooler:take_group_member(group_1),
                    ?assertEqual(ok, pooler:return_group_member(group_1, Pid))
                end},

                {"return error_no_member to group", fun() ->
                    ?assertEqual(ok, pooler:return_group_member(group_1, error_no_members))
                end},

                {"exhaust pools in group", fun() ->
                    Pids = get_n_pids_group(group_1, 6, []),
                    %% they should all be pids
                    [
                        begin
                            {Type, _} = pooled_gs:get_id(P),
                            ?assertMatch("type-1" ++ _, Type),
                            ok
                        end
                     || P <- Pids
                    ],
                    %% further attempts should be error
                    [
                        error_no_members,
                        error_no_members,
                        error_no_members
                    ] = [
                        pooler:take_group_member(group_1)
                     || _I <- lists:seq(1, 3)
                    ]
                end},

                {"rm_group with nonexisting group", fun() ->
                    ?assertEqual(ok, pooler:rm_group(i_dont_exist))
                end},

                {"rm_group with existing empty group", fun() ->
                    ?assertEqual(ok, pooler:rm_pool(test_pool_1)),
                    ?assertEqual(ok, pooler:rm_pool(test_pool_2)),
                    % process group de-registration is asynchronous
                    timer:sleep(100),
                    ?assertEqual(error_no_members, pooler:take_group_member(group_1)),
                    ?assertEqual(ok, pooler:rm_group(group_1)),

                    ?assertExit({noproc, _}, pooler:take_member(test_pool_1)),
                    ?assertExit({noproc, _}, pooler:take_member(test_pool_2)),
                    ?assertEqual(
                        error_no_members,
                        pooler:take_group_member(group_1)
                    )
                end},

                {"rm_group with existing non-empty group", fun() ->
                    %% Verify that group members exist
                    MemberPid = pooler:take_group_member(group_1),
                    ?assert(is_pid(MemberPid)),
                    pooler:return_group_member(group_1, MemberPid),

                    Pool1Pid = pooler:take_member(test_pool_1),
                    ?assert(is_pid(Pool1Pid)),
                    pooler:return_member(test_pool_1, Pool1Pid),

                    Pool2Pid = pooler:take_member(test_pool_2),
                    ?assert(is_pid(Pool2Pid)),
                    pooler:return_member(test_pool_2, Pool2Pid),

                    %% Delete and verify that group and pools are destroyed
                    ?assertEqual(ok, pooler:rm_group(group_1)),

                    ?assertExit({noproc, _}, pooler:take_member(test_pool_1)),
                    ?assertExit({noproc, _}, pooler:take_member(test_pool_2)),
                    ?assertEqual(
                        error_no_members,
                        pooler:take_group_member(group_1)
                    )
                end}
            ]}}.

pooler_limit_failed_adds_test_() ->
    %% verify that pooler crashes completely if too many failures are
    %% encountered while trying to add pids.
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pools = [
                [
                    {name, test_pool_1},
                    {max_count, 10},
                    {init_count, 10},
                    {start_mfa, {pooled_gs, start_link, [crash]}}
                ]
            ],
            application:set_env(pooler, pools, Pools)
        end,
        fun(_) ->
            application:stop(pooler)
        end,
        fun() ->
            application:start(pooler),
            ?assertEqual(error_no_members, pooler:take_member(test_pool_1)),
            ?assertEqual(error_no_members, pooler:take_member(test_pool_1))
        end}.

pooler_scheduled_cull_test_() ->
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link(),
            Pools = [
                [
                    {name, test_pool_1},
                    {max_count, 10},
                    {init_count, 2},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}},
                    {cull_interval, {200, ms}},
                    {max_age, {0, min}}
                ]
            ],
            application:set_env(pooler, pools, Pools),
            application:start(pooler)
        end,
        fun(_X) ->
            fake_metrics:stop(),
            application:stop(pooler)
        end,
        [
            {foreach,
                fun() ->
                    Pids = get_n_pids(test_pool_1, 10, []),
                    ?assertEqual(10, length(pooler:pool_stats(test_pool_1))),
                    ?assertEqual(10, length(Pids)),
                    Pids
                end,
                fun(Pids) ->
                    [pooler:return_member(test_pool_1, P) || P <- Pids]
                end,
                [
                    fun(Pids) ->
                        {"excess members are culled run 1", fun() ->
                            [pooler:return_member(test_pool_1, P) || P <- Pids],
                            %% wait for longer than cull delay
                            timer:sleep(250),
                            ?assertEqual(2, length(pooler:pool_stats(test_pool_1))),
                            ?assertEqual(2, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1)))
                        end}
                    end,

                    fun(Pids) ->
                        {"excess members are culled run 2", fun() ->
                            [pooler:return_member(test_pool_1, P) || P <- Pids],
                            %% wait for longer than cull delay
                            timer:sleep(250),
                            ?assertEqual(2, length(pooler:pool_stats(test_pool_1))),
                            ?assertEqual(2, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1)))
                        end}
                    end,

                    fun(Pids) -> in_use_members_not_culled(Pids, 1) end,
                    fun(Pids) -> in_use_members_not_culled(Pids, 2) end,
                    fun(Pids) -> in_use_members_not_culled(Pids, 3) end,
                    fun(Pids) -> in_use_members_not_culled(Pids, 4) end,
                    fun(Pids) -> in_use_members_not_culled(Pids, 5) end,
                    fun(Pids) -> in_use_members_not_culled(Pids, 6) end
                ]},

            {"no cull when init_count matches max_count",
                %% not sure how to verify this. But this test at least
                %% exercises the code path.
                fun() ->
                    Config = [
                        {name, test_static_pool_1},
                        {max_count, 2},
                        {init_count, 2},
                        {start_mfa, {pooled_gs, start_link, [{"static-0"}]}},
                        % ignored
                        {cull_interval, {200, ms}}
                    ],
                    pooler:new_pool(Config),
                    P = pooler:take_member(test_static_pool_1),
                    ?assertMatch({"static-0", _}, pooled_gs:get_id(P)),
                    pooler:return_member(test_static_pool_1, P),
                    ok
                end}
        ]}.

in_use_members_not_culled(Pids, N) ->
    {"in-use members are not culled " ++ erlang:integer_to_list(N), fun() ->
        %% wait for longer than cull delay
        timer:sleep(250),
        PidCount = length(Pids),
        ?assertEqual(
            PidCount,
            length(pooler:pool_stats(test_pool_1))
        ),
        ?assertEqual(0, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1))),
        ?assertEqual(PidCount, proplists:get_value(in_use_count, pooler:pool_utilization(test_pool_1))),
        Returns = lists:sublist(Pids, N),
        [
            pooler:return_member(test_pool_1, P)
         || P <- Returns
        ],
        timer:sleep(250),

        ?assertEqual(
            PidCount - N,
            length(pooler:pool_stats(test_pool_1))
        )
    end}.

random_message_test_() ->
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pools = [
                [
                    {name, test_pool_1},
                    {max_count, 2},
                    {init_count, 1},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}}
                ]
            ],
            application:set_env(pooler, pools, Pools),
            application:start(pooler),
            %% now send some bogus messages
            %% do the call in a throw-away process to avoid timeout error
            spawn(fun() -> catch gen_server:call(test_pool_1, {unexpected_garbage_msg, 5}) end),
            gen_server:cast(test_pool_1, {unexpected_garbage_msg, 6}),
            whereis(test_pool_1) ! {unexpected_garbage_msg, 7},
            ok
        end,
        fun(_) ->
            application:stop(pooler)
        end,
        [
            fun() ->
                Pid = spawn(fun() -> ok end),
                MonMsg = {'DOWN', erlang:make_ref(), process, Pid, because},
                test_pool_1 ! MonMsg
            end,

            fun() ->
                Pid = pooler:take_member(test_pool_1),
                {Type, _} = pooled_gs:get_id(Pid),
                ?assertEqual("type-0", Type)
            end,

            fun() ->
                RawPool = gen_server:call(test_pool_1, dump_pool),
                ?assertEqual(pool, maps:get('$record_name', RawPool))
            end
        ]}.

pooler_integration_long_init_test_() ->
    {foreach,
        % setup
        fun() ->
            logger:set_handler_config(default, filters, []),
            {ok, _} = error_logger_mon:start_link(),
            error_logger_mon:install_handler(pooler),
            Pool = [
                {name, test_pool_1},
                {max_count, 10},
                {init_count, 0},
                {member_start_timeout, {10, ms}},
                {start_mfa, {pooled_gs, start_link, [{"type-0", fun() -> timer:sleep(15) end}]}}
            ],

            application:set_env(pooler, pools, [Pool]),
            application:start(pooler)
        end,
        % cleanup
        fun(_) ->
            error_logger_mon:uninstall_handler(),
            ok = error_logger_mon:stop(),
            application:stop(pooler)
        end,
        %
        [
            fun(_) ->
                % Test what happens when pool members take too long to start.
                % The pooler_starter should kill off stale members, there by
                % reducing the number of children of the member_sup. This
                % activity occurs both during take member and accept member.
                % Accordingly, the count should go to zero once all starters
                % check in.
                fun() ->
                    ?assertEqual(0, children_count(pooler_test_pool_1_member_sup)),
                    [
                        begin
                            ?assertEqual(error_no_members, pooler:take_member(test_pool_1)),
                            ?assertEqual(1, starting_members(test_pool_1))
                        end
                     || _ <- lists:seq(1, 10)
                    ],
                    ?assertEqual(10, children_count(pooler_test_pool_1_member_sup)),

                    timer:sleep(150),
                    ?assertEqual(0, children_count(pooler_test_pool_1_member_sup)),
                    ?assertEqual(0, starting_members(test_pool_1)),
                    %% there is a log when worker start times out
                    ?assert(
                        lists:any(
                            fun
                                (
                                    #{
                                        level := error,
                                        msg :=
                                            {report, #{
                                                label := "starting member timeout",
                                                pool := test_pool_1
                                            }}
                                    }
                                ) ->
                                    true;
                                (_) ->
                                    false
                            end,
                            error_logger_mon:get_msgs()
                        )
                    )
                end
            end
        ]}.

sleep_for_configured_timeout() ->
    SleepTime =
        case application:get_env(pooler, sleep_time) of
            {ok, Val} ->
                Val;
            _ ->
                0
        end,
    timer:sleep(SleepTime).

pooler_integration_queueing_test_() ->
    {foreach,
        % setup
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pool = [
                {name, test_pool_1},
                {max_count, 10},
                {queue_max, 10},
                {init_count, 0},
                {metrics, fake_metrics},
                {member_start_timeout, {5, sec}},
                {start_mfa,
                    {pooled_gs, start_link, [
                        {"type-0", fun pooler_tests:sleep_for_configured_timeout/0}
                    ]}}
            ],

            application:set_env(pooler, pools, [Pool]),
            fake_metrics:start_link(),
            application:start(pooler)
        end,
        % cleanup
        fun(_) ->
            fake_metrics:stop(),
            application:stop(pooler)
        end,
        [
            fun(_) ->
                fun() ->
                    ?assertEqual(0, maps:get(free_count, dump_pool(test_pool_1))),
                    Val = pooler:take_member(test_pool_1, 10),
                    ?assert(is_pid(Val)),
                    pooler:return_member(test_pool_1, Val)
                end
            end,
            fun(_) ->
                fun() ->
                    application:set_env(pooler, sleep_time, 1),
                    ?assertEqual(0, maps:get(free_count, dump_pool(test_pool_1))),
                    Val = pooler:take_member(test_pool_1, 0),
                    ?assertEqual(error_no_members, Val),
                    ?assertEqual(0, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1))),
                    timer:sleep(50),
                    %Next request should be available
                    Pid = pooler:take_member(test_pool_1, 0),
                    ?assert(is_pid(Pid)),
                    pooler:return_member(test_pool_1, Pid)
                end
            end,
            fun(_) ->
                fun() ->
                    application:set_env(pooler, sleep_time, 10),
                    ?assertEqual(0, maps:get(free_count, dump_pool(test_pool_1))),
                    [
                        ?assertEqual(pooler:take_member(test_pool_1, 0), error_no_members)
                     || _ <- lists:seq(1, maps:get(max_count, dump_pool(test_pool_1)))
                    ],
                    timer:sleep(50),
                    %Next request should be available
                    Pid = pooler:take_member(test_pool_1, 0),
                    ?assert(is_pid(Pid)),
                    pooler:return_member(test_pool_1, Pid)
                end
            end,
            fun(_) ->
                fun() ->
                    % fill to queue_max, next request should return immediately with no_members
                    % Will return a if queue max is not enforced.
                    application:set_env(pooler, sleep_time, 100),
                    [
                        proc_lib:spawn(fun() ->
                            Val = pooler:take_member(test_pool_1, 200),
                            ?assert(is_pid(Val)),
                            pooler:return_member(Val)
                        end)
                     || _ <- lists:seq(1, maps:get(max_count, dump_pool(test_pool_1)))
                    ],
                    ?assertEqual(0, proplists:get_value(free_count, pooler:pool_utilization(test_pool_1))),
                    ?assert(proplists:get_value(queued_count, pooler:pool_utilization(test_pool_1)) >= 1),
                    ?assertEqual(10, proplists:get_value(queue_max, pooler:pool_utilization(test_pool_1))),

                    timer:sleep(50),
                    ?assertEqual(10, queue:len(maps:get(queued_requestors, dump_pool(test_pool_1)))),
                    ?assertEqual(10, proplists:get_value(queue_max, pooler:pool_utilization(test_pool_1))),

                    ?assertEqual(pooler:take_member(test_pool_1, 500), error_no_members),
                    ExpectKeys = lists:sort([
                        <<"pooler.test_pool_1.error_no_members_count">>,
                        <<"pooler.test_pool_1.events">>,
                        <<"pooler.test_pool_1.take_rate">>,
                        <<"pooler.test_pool_1.queue_count">>,
                        <<"pooler.test_pool_1.queue_max_reached">>
                    ]),
                    Metrics = fake_metrics:get_metrics(),
                    GotKeys = lists:usort([Name || {Name, _, _} <- Metrics]),
                    ?assertEqual(ExpectKeys, GotKeys),

                    timer:sleep(100),
                    Val = pooler:take_member(test_pool_1, 500),
                    ?assert(is_pid(Val)),
                    pooler:return_member(test_pool_1, Val)
                end
            end
        ]}.
pooler_integration_queueing_return_member_test_() ->
    {foreach,
        % setup
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pool = [
                {name, test_pool_1},
                {max_count, 10},
                {queue_max, 10},
                {init_count, 10},
                {metrics, fake_metrics},
                {member_start_timeout, {5, sec}},
                {start_mfa,
                    {pooled_gs, start_link, [
                        {"type-0", fun pooler_tests:sleep_for_configured_timeout/0}
                    ]}}
            ],

            application:set_env(pooler, pools, [Pool]),
            fake_metrics:start_link(),
            application:start(pooler)
        end,
        % cleanup
        fun(_) ->
            fake_metrics:stop(),
            application:stop(pooler)
        end,
        [
            fun(_) ->
                fun() ->
                    application:set_env(pooler, sleep_time, 0),
                    Parent = self(),
                    Pids = [
                        proc_lib:spawn_link(fun() ->
                            Val = pooler:take_member(test_pool_1, 200),
                            ?assert(is_pid(Val)),
                            Parent ! {taken, self()},
                            receive
                                return ->
                                    pooler:return_member(test_pool_1, Val)
                            after 5000 ->
                                pooler:return_member(test_pool_1, Val)
                            end,
                            Parent ! {returned, self()}
                        end)
                     || _ <- lists:seq(1, maps:get(max_count, dump_pool(test_pool_1)))
                    ],
                    [
                        receive
                            {taken, Pid} -> ok
                        end
                     || Pid <- Pids
                    ],
                    ?assertEqual(error_no_members, pooler:take_member(test_pool_1)),
                    proc_lib:spawn_link(fun() ->
                        Val = pooler:take_member(test_pool_1, 200),
                        Parent ! {extra_result, Val}
                    end),
                    [Pid ! return || Pid <- Pids],
                    [
                        receive
                            {returned, Pid} -> ok
                        end
                     || Pid <- Pids
                    ],
                    receive
                        {extra_result, Result} ->
                            ?assert(is_pid(Result)),
                            pooler:return_member(test_pool_1, Result)
                    end,
                    ?assertEqual(
                        maps:get(max_count, dump_pool(test_pool_1)),
                        length(maps:get(free_pids, dump_pool(test_pool_1)))
                    ),
                    ?assertEqual(
                        maps:get(max_count, dump_pool(test_pool_1)),
                        maps:get(free_count, dump_pool(test_pool_1))
                    )
                end
            end
        ]}.

pooler_integration_test_() ->
    {foreach,
        % setup
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pools = [
                [
                    {name, test_pool_1},
                    {max_count, 10},
                    {init_count, 10},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}}
                ]
            ],
            application:set_env(pooler, pools, Pools),
            application:start(pooler),
            Users = [start_user() || _X <- lists:seq(1, 10)],
            Users
        end,
        % cleanup
        fun(Users) ->
            [user_stop(U) || U <- Users],
            application:stop(pooler)
        end,
        %
        [
            fun(Users) ->
                fun() ->
                    % each user has a different tc ID
                    TcIds = lists:sort([user_id(UPid) || UPid <- Users]),
                    ?assertEqual(lists:usort(TcIds), TcIds)
                end
            end,

            fun(Users) ->
                fun() ->
                    % users still unique after a renew cycle
                    [user_new_tc(UPid) || UPid <- Users],
                    TcIds = lists:sort([user_id(UPid) || UPid <- Users]),
                    ?assertEqual(lists:usort(TcIds), TcIds)
                end
            end,

            fun(Users) ->
                fun() ->
                    % all users crash, pids are replaced
                    TcIds1 = lists:sort([user_id(UPid) || UPid <- Users]),
                    [user_crash(UPid) || UPid <- Users],
                    Seq = lists:seq(1, 5),
                    Users2 = [start_user() || _X <- Seq],
                    TcIds2 = lists:sort([user_id(UPid) || UPid <- Users2]),
                    Both =
                        sets:to_list(
                            sets:intersection([
                                sets:from_list(TcIds1),
                                sets:from_list(TcIds2)
                            ])
                        ),
                    ?assertEqual([], Both)
                end
            end
        ]}.

pooler_auto_grow_disabled_by_default_test_() ->
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                Pool = [
                    {name, test_pool_1},
                    {max_count, 5},
                    {init_count, 2},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}}
                ],
                application:unset_env(pooler, pools),
                application:start(pooler),
                pooler:new_pool(Pool)
            end,
            fun(_X) ->
                application:stop(pooler)
            end,
            [
                {"take one, and it should not auto-grow", fun() ->
                    ?assertEqual(2, maps:get(free_count, dump_pool(test_pool_1))),
                    P = pooler:take_member(test_pool_1),
                    ?assertMatch({"type-0", _Id}, pooled_gs:get_id(P)),
                    timer:sleep(100),
                    ?assertEqual(1, maps:get(free_count, dump_pool(test_pool_1))),
                    ok,
                    pooler:return_member(test_pool_1, P)
                end}
            ]}}.

pooler_auto_grow_enabled_test_() ->
    {setup,
        fun() ->
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            fake_metrics:stop()
        end,
        {foreach,
            % setup
            fun() ->
                Pool = [
                    {name, test_pool_1},
                    {max_count, 5},
                    {init_count, 2},
                    {auto_grow_threshold, 1},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}}
                ],
                application:unset_env(pooler, pools),
                application:start(pooler),
                pooler:new_pool(Pool)
            end,
            fun(_X) ->
                application:stop(pooler)
            end,
            [
                {"take one, and it should grow by 2", fun() ->
                    ?assertEqual(2, maps:get(free_count, dump_pool(test_pool_1))),
                    P = pooler:take_member(test_pool_1),
                    ?assertMatch({"type-0", _Id}, pooled_gs:get_id(P)),
                    timer:sleep(100),
                    ?assertEqual(3, maps:get(free_count, dump_pool(test_pool_1))),
                    ok,
                    pooler:return_member(test_pool_1, P)
                end}
            ]}}.

pooler_custom_stop_mfa_test_() ->
    {foreach,
        fun() ->
            logger:set_handler_config(default, filters, []),
            Pool = [
                {name, test_pool_1},
                {max_count, 3},
                {init_count, 2},
                {cull_interval, {200, ms}},
                {max_age, {0, min}},
                {start_mfa, {pooled_gs, start_link, [{foo_type}]}}
            ],
            application:set_env(pooler, pools, [Pool])
        end,
        fun(_) ->
            application:unset_env(pooler, pools)
        end,
        [
            {"default behavior kills the pool member", fun() ->
                ok = application:start(pooler),
                Reason = monitor_members_trigger_culling_and_return_reason(),
                ok = application:stop(pooler),
                ?assertEqual(killed, Reason)
            end},
            {"custom callback terminates the pool member normally", fun() ->
                {ok, [Pool]} = application:get_env(pooler, pools),
                Stop = {stop_mfa, {pooled_gs, stop, ['$pooler_pid']}},
                application:set_env(pooler, pools, [[Stop | Pool]]),
                ok = application:start(pooler),
                Reason = monitor_members_trigger_culling_and_return_reason(),
                ok = application:stop(pooler),
                ?assertEqual(normal, Reason)
            end}
        ]}.

no_error_logger_reports_after_culling_test_() ->
    %% damn those wraiths! This is the cure
    {foreach,
        fun() ->
            logger:set_handler_config(default, filters, []),
            {ok, _Pid} = error_logger_mon:start_link(),
            Pool = [
                {name, test_pool_1},
                {max_count, 3},
                {init_count, 2},
                {cull_interval, {200, ms}},
                {max_age, {0, min}},
                {start_mfa, {pooled_gs, start_link, [{type}]}}
            ],
            application:set_env(pooler, pools, [Pool])
        end,
        fun(_) ->
            ok = error_logger_mon:stop(),
            error_logger_mon:uninstall_handler(),
            application:unset_env(pooler, pools)
        end,
        [
            {"Force supervisor to report by using exit/2 instead of terminate_child", fun() ->
                {ok, [Pool]} = application:get_env(pooler, pools),
                Stop = {stop_mfa, {erlang, exit, ['$pooler_pid', kill]}},
                application:set_env(pooler, pools, [[Stop | Pool]]),
                ok = application:start(pooler),
                error_logger_mon:install_handler(),
                error_logger_mon:reset(),
                Reason = monitor_members_trigger_culling_and_return_reason(),
                %% we need to wait for the message to arrive before deleting handler
                timer:sleep(250),
                error_logger_mon:uninstall_handler(),
                ok = application:stop(pooler),
                ?assertEqual(killed, Reason),
                ?assertEqual(
                    1,
                    error_logger_mon:get_msg_count(),
                    [
                        {msgs, error_logger_mon:get_msgs()},
                        {m, [R || #{msg := {report, R}} <- error_logger_mon:get_msgs()]}
                    ]
                )
            end},
            {"Default MFA shouldn't generate any reports during culling", fun() ->
                ok = application:start(pooler),
                error_logger_mon:install_handler(),
                Reason = monitor_members_trigger_culling_and_return_reason(),
                error_logger_mon:uninstall_handler(),
                ok = application:stop(pooler),
                ?assertEqual(killed, Reason),
                ?assertEqual(0, error_logger_mon:get_msg_count())
            end}
        ]}.

reconfigure_test_() ->
    Name = test_pool_1,
    InitCount = 2,
    MaxCount = 4,
    StartConfig = #{
        name => Name,
        max_count => MaxCount,
        init_count => InitCount,
        start_mfa => {pooled_gs, start_link, [{reconfigure_test}]}
    },
    {foreach,
        fun() ->
            logger:set_handler_config(default, filters, []),
            application:set_env(pooler, pools, [StartConfig]),
            application:set_env(pooler, metrics_module, pooler_no_metrics),
            application:start(pooler)
        end,
        fun(_) ->
            application:unset_env(pooler, pools),
            application:stop(pooler)
        end,
        [
            {"Raise init_count", fun() ->
                Config1 = StartConfig#{init_count => 3},
                ?assertEqual(
                    {ok, [
                        {set_parameter, {init_count, 3}},
                        {start_workers, 1}
                    ]},
                    pooler:pool_reconfigure(Name, Config1)
                ),
                ?assertMatch(
                    #{
                        init_count := 3,
                        free_count := 3,
                        free_pids := [_, _, _]
                    },
                    wait_for_dump(Name, 5000, fun(#{free_count := C}) -> C =:= 3 end)
                )
            end},
            {"Lower max_count", fun() ->
                Config1 = StartConfig#{max_count => 1, init_count => 1},
                ?assertEqual(
                    {ok, [
                        {set_parameter, {init_count, 1}},
                        {set_parameter, {max_count, 1}},
                        {stop_free_workers, 1}
                    ]},
                    pooler:pool_reconfigure(Name, Config1)
                ),
                ?assertMatch(
                    #{
                        init_count := 1,
                        max_count := 1,
                        free_count := 1,
                        free_pids := [_]
                    },
                    wait_for_dump(Name, 5000, fun(#{free_count := C}) -> C =:= 1 end)
                )
            end},
            {"Lower queue_max", fun() ->
                NewQMax = 4,
                NewConfig = StartConfig#{queue_max => NewQMax},
                Parent = self(),
                NumClients = 10,
                _Clients = lists:map(
                    fun(_) ->
                        spawn_link(
                            fun() ->
                                Parent ! pooler:take_member(Name, 60000),
                                timer:sleep(60000)
                            end
                        )
                    end,
                    lists:seq(1, NumClients)
                ),
                timer:sleep(100),
                % 6
                QueueSize = NumClients - MaxCount,
                %2
                Shrink = QueueSize - NewQMax,
                ?assertEqual(
                    {ok, [
                        {set_parameter, {queue_max, NewQMax}},
                        {shrink_queue, Shrink}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig)
                ),
                ?assertMatch(
                    [
                        W1,
                        W2,
                        W3,
                        W4,
                        error_no_members,
                        error_no_members
                    ] when
                        is_pid(W1) andalso
                            is_pid(W2) andalso
                            is_pid(W3) andalso
                            is_pid(W4),
                    [
                        receive
                            M -> M
                        after 5000 -> error(timeout)
                        end
                     || _ <- lists:seq(1, MaxCount + Shrink)
                    ]
                ),
                #{
                    queue_max := QMax,
                    queued_requestors := Q
                } = gen_server:call(Name, dump_pool),
                % queue_max in the state is updated
                ?assertEqual(QMax, NewQMax),
                % queue is full
                ?assertEqual(NewQMax, queue:len(Q))
            end},
            {"Lower cull_interval", fun() ->
                NewConfig = StartConfig#{cull_interval => {10, sec}},
                ?assertEqual(
                    {ok, [
                        {set_parameter, {cull_interval, {10, sec}}},
                        {reset_cull_timer, {10, sec}}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig)
                )
            end},
            {"Lower max_age", fun() ->
                NewConfig = StartConfig#{max_age => {100, ms}},
                Workers = [pooler:take_member(Name, 5000) || _ <- lists:seq(1, MaxCount)],
                [pooler:return_member(Name, Pid) || Pid <- Workers],
                ?assertEqual(
                    {ok, [
                        {set_parameter, {max_age, {100, ms}}},
                        {cull, []}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig)
                ),
                %% make sure workers are culled
                wait_for_dump(
                    Name,
                    1000,
                    fun(#{free_count := Free}) ->
                        Name ! cull_pool,
                        Free =:= InitCount
                    end
                )
            end},
            {"Update group", fun() ->
                NewConfig1 = StartConfig#{group => my_group1},
                ?assertEqual(
                    {ok, [
                        {set_parameter, {group, my_group1}},
                        {join_group, my_group1}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig1)
                ),
                PoolPid = whereis(Name),
                ?assertMatch([PoolPid], pooler:group_pools(my_group1)),
                NewConfig2 = StartConfig#{group => my_group2},
                ?assertEqual(
                    {ok, [
                        {set_parameter, {group, my_group2}},
                        {leave_group, my_group1},
                        {join_group, my_group2}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig2)
                ),
                ?assertMatch([], pooler:group_pools(my_group1)),
                ?assertMatch([PoolPid], pooler:group_pools(my_group2)),
                ?assertEqual(
                    {ok, [
                        {set_parameter, {group, undefined}},
                        {leave_group, my_group2}
                    ]},
                    pooler:pool_reconfigure(Name, StartConfig)
                ),
                ?assertMatch([], pooler:group_pools(my_group1)),
                ?assertMatch([], pooler:group_pools(my_group2))
            end},
            {"Change basic configs", fun() ->
                NewMaxCount = MaxCount + 5,
                NewConfig = StartConfig#{
                    max_count => NewMaxCount,
                    member_start_timeout => {10, sec},
                    queue_max => 100,
                    metrics_mod => fake_metrics,
                    stop_mfa => {erlang, exit, ['$pooler_pid', shutdown]},
                    auto_grow_threshold => 1
                },
                ?assertEqual(
                    {ok, [
                        {set_parameter, {max_count, NewMaxCount}},
                        {set_parameter, {member_start_timeout, {10, sec}}},
                        {set_parameter, {queue_max, 100}},
                        {set_parameter, {metrics_mod, fake_metrics}},
                        {set_parameter, {stop_mfa, {erlang, exit, ['$pooler_pid', shutdown]}}},
                        {set_parameter, {auto_grow_threshold, 1}}
                    ]},
                    pooler:pool_reconfigure(Name, NewConfig)
                ),
                ?assertMatch(
                    #{
                        max_count := NewMaxCount,
                        member_start_timeout := {10, sec},
                        queue_max := 100,
                        metrics_mod := fake_metrics,
                        stop_mfa := {erlang, exit, ['$pooler_pid', shutdown]},
                        auto_grow_threshold := 1
                    },
                    gen_server:call(Name, dump_pool)
                )
            end},
            {"Update failed", fun() ->
                ?assertEqual(
                    {error, changed_unsupported_parameter},
                    pooler:pool_reconfigure(
                        Name, StartConfig#{start_mfa := {erlang, spawn, [a, b, []]}}
                    )
                ),
                ?assertEqual(
                    {error, changed_unsupported_parameter},
                    pooler:pool_reconfigure(
                        Name, StartConfig#{name := not_a_pool_name}
                    )
                )
            end}
        ]}.

wait_for_dump(Pool, Timeout, Fun) when Timeout > 0 ->
    Dump = gen_server:call(Pool, dump_pool),
    case Fun(Dump) of
        true ->
            Dump;
        false ->
            timer:sleep(50),
            wait_for_dump(Pool, Timeout - 50, Fun)
    end;
wait_for_dump(_, _, _) ->
    error(timeout).

monitor_members_trigger_culling_and_return_reason() ->
    Pids = get_n_pids(test_pool_1, 3, []),
    [erlang:monitor(process, P) || P <- Pids],
    [pooler:return_member(test_pool_1, P) || P <- Pids],
    receive
        {'DOWN', _Ref, process, _Pid, Reason} ->
            Reason
    after 250 -> timeout
    end.

time_as_millis_test_() ->
    Zeros = [{{0, U}, 0} || U <- [min, sec, ms, mu]],
    Ones = [
        {{1, min}, 60000},
        {{1, sec}, 1000},
        {{1, ms}, 1},
        {{1, mu}, 0}
    ],
    Misc = [{{3000, mu}, 3}],
    Tests = Zeros ++ Ones ++ Misc,
    [?_assertEqual(E, pooler:time_as_millis(I)) || {I, E} <- Tests].

time_as_micros_test_() ->
    Zeros = [{{0, U}, 0} || U <- [min, sec, ms, mu]],
    Ones = [
        {{1, min}, 60000000},
        {{1, sec}, 1000000},
        {{1, ms}, 1000},
        {{1, mu}, 1}
    ],
    Misc = [{{3000, mu}, 3000}],
    Tests = Zeros ++ Ones ++ Misc,
    [?_assertEqual(E, pooler:time_as_micros(I)) || {I, E} <- Tests].

call_free_members_test_() ->
    NumWorkers = 10,
    PoolName = test_pool_1,

    {setup,
        fun() ->
            application:set_env(pooler, metrics_module, fake_metrics),
            fake_metrics:start_link()
        end,
        fun(_X) ->
            fake_metrics:stop()
        end,
        {foreach,
            fun() ->
                Pool = [
                    {name, PoolName},
                    {max_count, NumWorkers},
                    {init_count, NumWorkers},
                    {start_mfa, {pooled_gs, start_link, [{"type-0"}]}}
                ],
                application:unset_env(pooler, pools),
                application:start(pooler),
                pooler:new_pool(Pool)
            end,
            fun(_X) ->
                application:stop(pooler)
            end,
            [
                {"perform a ping across the pool when all workers are free", fun() ->
                    ?assertEqual(NumWorkers, maps:get(free_count, dump_pool(PoolName))),
                    Res = pooler:call_free_members(PoolName, fun pooled_gs:ping/1),

                    ?assertEqual(NumWorkers, count_pongs(Res))
                end},
                {"perform a ping across the pool when two workers are taken", fun() ->
                    ?assertEqual(NumWorkers, maps:get(free_count, dump_pool(PoolName))),
                    Pids = [pooler:take_member(PoolName) || _X <- lists:seq(0, 1)],
                    Res = pooler:call_free_members(PoolName, fun pooled_gs:ping/1),

                    ?assertEqual(NumWorkers - 2, count_pongs(Res)),

                    [pooler:return_member(PoolName, P) || P <- Pids]
                end},
                {"perform an op where the op crashes all free members", fun() ->
                    ?assertEqual(NumWorkers, maps:get(free_count, dump_pool(PoolName))),
                    Res = pooler:call_free_members(
                        PoolName,
                        fun pooled_gs:error_on_call/1
                    ),

                    ?assertEqual(NumWorkers, count_errors(Res))
                end}
            ]}}.

count_pongs(Result) ->
    lists:foldl(
        fun
            ({ok, pong}, Acc) -> Acc + 1;
            ({error, _}, Acc) -> Acc
        end,
        0,
        Result
    ).

count_errors(Result) ->
    lists:foldl(
        fun
            ({error, _}, Acc) -> Acc + 1;
            ({ok, _}, Acc) -> Acc
        end,
        0,
        Result
    ).

% testing crash recovery means race conditions when either pids
% haven't yet crashed or pooler hasn't recovered.  So this helper loops
% forver until N pids are obtained, ignoring error_no_members.
get_n_pids(N, Acc) ->
    get_n_pids(test_pool_1, N, Acc).

get_n_pids(_Pool, 0, Acc) ->
    Acc;
get_n_pids(Pool, N, Acc) ->
    case pooler:take_member(Pool) of
        error_no_members ->
            get_n_pids(Pool, N, Acc);
        Pid ->
            get_n_pids(Pool, N - 1, [Pid | Acc])
    end.

get_n_pids_group(_Group, 0, Acc) ->
    Acc;
get_n_pids_group(Group, N, Acc) ->
    case pooler:take_group_member(Group) of
        error_no_members ->
            get_n_pids_group(Group, N, Acc);
        Pid ->
            get_n_pids_group(Group, N - 1, [Pid | Acc])
    end.

children_count(SupId) ->
    length(supervisor:which_children(SupId)).

starting_members(PoolName) ->
    length(maps:get(starting_members, dump_pool(PoolName))).

dump_pool(PoolName) ->
    gen_server:call(PoolName, dump_pool).

% >= OTP-21
-ifdef(OTP_RELEASE).
-if(?OTP_RELEASE >= 23).
-define(USE_PG_NOT_PG2, true).
-else.
-undef(USE_PG_NOT_PG2).
-endif.
% < OTP-21
-else.
-undef(USE_PG_NOT_PG2).
-endif.

-ifdef(USE_PG_NOT_PG2).

pg_start() ->
    pg:start(_Scope = 'pg').

pg_stop() ->
    lists:foreach(
        fun(Group) -> pg:leave(Group, pg:get_members(Group)) end,
        pg:which_groups()
    ).

pg_leave(Group, Pid) ->
    pg:leave(Group, Pid).

-else.

pg_start() ->
    pg2:start().

pg_stop() ->
    application:stop(pg2).

pg_leave(Group, Pid) ->
    pg2:leave(Group, Pid).

-endif.