Simple use of jobs application failing

[Ulf Wiger]

Well, you can.

4> jobs:add_queue(becka,
[{regulators,[{counter,[{limit,3}]}]},{max_size,3}]).
ok
5> [spawn(fun() -> Res = jobs:ask(becka), io:fwrite("~p --> ~p: ~p~n",
[Res, time(), self()]), timer:sleep(3000), exit(normal) end) || _ <-
lists:seq(1,10)].
{ok,{#Ref<0.4079473062.3785097227.122199>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,46}: <0.4192.0>
{ok,{#Ref<0.4079473062.3785097227.122196>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,46}: <0.4191.0>
{ok,{#Ref<0.4079473062.3785097227.122202>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,46}: <0.4193.0>
{error,rejected} --> {7,6,46}: <0.4197.0>
{error,rejected} --> {7,6,46}: <0.4198.0>
{error,rejected} --> {7,6,46}: <0.4199.0>
{error,rejected} --> {7,6,46}: <0.4200.0>
[<0.4191.0>,<0.4192.0>,<0.4193.0>,<0.4194.0>,<0.4195.0>,
 <0.4196.0>,<0.4197.0>,<0.4198.0>,<0.4199.0>,<0.4200.0>]
{ok,{#Ref<0.4079473062.3785097217.122718>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,49}: <0.4194.0>
{ok,{#Ref<0.4079473062.3785097217.122720>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,49}: <0.4195.0>
{ok,{#Ref<0.4079473062.3785097217.122721>,
     [{counters,[{{counter,becka,1},1}]}]}} --> {7,6,49}: <0.4196.0>

So, basically, the first three requests were served and removed from the
queue. Meanwhile, a bunch of requests were rejected due to the size limit.
Eventually, a few new requests were able to enter. After 3 seconds (when
the first 3 workers woke up and finished), they were able to run. Now the
queue is empty again.

BR,
UIf W

On Sun, Nov 14, 2021 at 11:13 PM bengt <cean.ebengt@REDACTED> wrote:

> Thank you very much. With this explanation I should get my application
> properly limited.
>
> One thing though, is it not possible to get an error from jobs:ask/1 ?
> Like {error, Reason}
> when the queue is full? That is, jobs:done/1 have not been called for the
> previous 3  {ok, X}.
>
> bengt
>
> On 14 Nov 2021, at 19:55, Ulf Wiger <ulf@REDACTED> wrote:
>
> In jobs, `max_size` has to do with how large the queue is allowed to get.
> What you appear to be looking for is `counter`.
>
> Example:
> Eshell V10.7.2.8  (abort with ^G)
> 1> application:ensure_all_started(jobs).
> {ok,[jobs]}
> 2> jobs:add_queue(kalle, [{standard_counter,3}]).
> ok
> 3> [spawn(fun() -> jobs:ask(kalle), io:fwrite("--> ~p: ~p~n", [time(),
> self()]), timer:sleep(3000), exit(normal) end) || _ <- lists:seq(1,10)].
> --> {19,53,29}: <0.128.0>
> --> {19,53,29}: <0.129.0>
> --> {19,53,29}: <0.130.0>
> [<0.128.0>,<0.129.0>,<0.130.0>,<0.131.0>,<0.132.0>,
>  <0.133.0>,<0.134.0>,<0.135.0>,<0.136.0>,<0.137.0>]
> --> {19,53,32}: <0.131.0>
> --> {19,53,32}: <0.133.0>
> --> {19,53,32}: <0.132.0>
> --> {19,53,35}: <0.134.0>
> --> {19,53,35}: <0.135.0>
> --> {19,53,35}: <0.136.0>
> --> {19,53,38}: <0.137.0>
>
> From the docs:
> "{standard_counter, C} - equivalent to [{regulators,[{counter,[{limit,C},
> {modifiers,[{cpu,10},{memory,10}]}]}]}]"
>
> (Usually, one doesn't specify the modifiers)
>
> BR,
> Ulf
>
> On Sat, Nov 13, 2021 at 6:12 PM bengt <cean.ebengt@REDACTED> wrote:
>
>> Greetings,
>>
>> I would like to allow at most 3 processes to call a gen_server at the
>> same time. I could check the message queue length, but why not use jobs (
>> https://github.com/uwiger/jobs) ?
>>
>> Jobs is already in use by something I depend on, so it should be working.
>> I test from the (iex) shell. As can be seen below I am making a mistake
>> somewhere. Probably config, so how should I configure to only get 3 of the
>> 5 jobs:ask/1 to be approved and queued? Or I have misunderstood the use,
>> and an explanation of how to achieve the 3 caller limitation would be
>> appreciated.
>>
>>  :jobs.add_queue(:kalle,  [{:max_size, 3}])
>>   for _ <- [1,2,3,4,5], do: :jobs.ask(:kalle)
>>   IO.inspect :jobs.queue_info(:kalle)
>>
>>    name: :kalle,
>>    max_size: 3,
>>    approved: 5,
>>    queued: 5,
>>    latest_dispatch: 378734152926266,
>>    mod: :jobs_queue,
>>    type: :fifo,
>>    group: :undefined,
>>    regulators: [],
>>    max_time: :undefined,
>>    check_interval: :infinity,
>>    oldest_job: :undefined,
>>    timer: :undefined,
>>    link_ref: :undefined,
>>    check_counter: 0,
>>    empty: false,
>>    depleted: false,
>>    waiters: [],
>>    stateful: :undefined,
>>    st: {:st, #Reference<0.2285429207.3584425985.10312>},
>>    producers: []
>>
>> Best Wishes,
>> bengt
>
>
>
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