> And this made me wonder: is there any reason why you can't use Task.async_stream?
After testing, I'm sure we can accomplish the same thing that was proposed with Task.async_stream. There is really no reason for an extra function. One thing that would be nice is to have an example for this usage in the documentation. I honestly never thought in using Task.async_stream in this way. WDYT? PRs for adding this example to the documentation would be welcome? Em sexta-feira, 2 de abril de 2021 às 08:39:18 UTC-3, [email protected] escreveu: > Funny that exactly on this day that the proposal was opened I said in two > groups the lack that I was doing something similar to "Promise.any" in > Elixir. > > I needed it and found it complicated to do now, I had a job because I'm > starting in Elixir. > > I would love to have another solution for what I did, when researching > several APIs to return the CEP query to me and get the first valid result. > > I'm starting in Elixir and in love, and I made my first package with > exactly this need: > https://github.com/ciareis/cep-promise-elixir/blob/master/lib/cep_promise.ex#L52 > > I could probably write everything in a better way, but I still get there. > > Please implement something to facilitate this;) > > Elixir S2! > Em sexta-feira, 2 de abril de 2021 às 04:51:53 UTC-3, José Valim escreveu: > >> I have been thinking more about this problem and there is still one issue >> for us to solve: when you say you are waiting for "n" tasks, does it mean >> you are waiting for "n" successes or "n" results (regardless if they are >> success or failure)? >> >> So I thought perhaps a better solution is to introduce something called >> Task.yield_stream/2. "yield_stream" receives an enumerable of tasks and >> emits them as they complete. To get the first successful task you would do: >> >> tasks >> |> Task.yield_stream(ordered: false, timeout: 5000) >> |> Stream.filter(&match?({:ok, _})) >> |> Enum.at(0) >> >> And this made me wonder: is there any reason why you can't use >> Task.async_stream? >> >> >> On Thu, Apr 1, 2021 at 3:59 PM José Valim <[email protected]> wrote: >> >>> I don't see a reason why we wouldn't return the same order. You can >>> easily get the ones you want by `for {task, {:ok, value}} <- result do`. >>> Plus forcing people to iterate will remind them that they most likely need >>> to shutdown the other tasks. >>> >>> On Thu, Apr 1, 2021 at 3:57 PM [email protected] < >>> [email protected]> wrote: >>> >>>> > In this sense, yield_many becomes a special case of yield_first where >>>> you want to yield on all given tasks. >>>> >>>> I'm not sure if we would want that, because in yield_many the returned >>>> list will be in the same order as the tasks supplied in the tasks >>>> input argument. >>>> However yield_first to preserve the semantics of "returning as soon it >>>> finishes", maybe we should return the tasks in the order of finish (the >>>> first to complete first in the list). >>>> That makes sense? >>>> >>>> Em quarta-feira, 31 de março de 2021 às 19:35:47 UTC-3, >>>> [email protected] escreveu: >>>> >>>>> +1 for yield_first(tasks, n, timeout) >>>>> >>>>> It seems to better convey the meaning "yield the first n tasks". >>>>> >>>>> Em qua., 31 de mar. de 2021 às 19:26, Felipe Stival <[email protected]> >>>>> escreveu: >>>>> >>>>>> +1 for yield_first(tasks, n, timeout) >>>>>> >>>>>> >>>>>> On Thu, Apr 1, 2021, 01:11 José Valim <[email protected]> wrote: >>>>>> >>>>>>> It was not possible to implement yield_first in Elixir but now that >>>>>>> we have map_get in guards, we can easily do so by putting all refs in a >>>>>>> map >>>>>>> and only getting messages from the inbox where the ref is in the map. >>>>>>> The >>>>>>> number of tasks to wait and the maximum timeout should be configurable >>>>>>> too. >>>>>>> For example: >>>>>>> >>>>>>> yield_first(task, 3, 1000) >>>>>>> >>>>>>> The above will yield the first 3 tasks within 1000ms. It should have >>>>>>> the same result type as yield_many. In this sense, yield_many becomes a >>>>>>> special case of yield_first where you want to yield on all given tasks. >>>>>>> >>>>>>> Another option is to not introduce a new function but instead >>>>>>> introduce a new argument to yield_many with the limit to yield: >>>>>>> >>>>>>> yield_many(task, 1000, 3) >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Wed, Mar 31, 2021 at 11:52 PM [email protected] < >>>>>>> [email protected]> wrote: >>>>>>> >>>>>>>> I think the proposal would work differently from yield_many. >>>>>>>> yield_many "receives a list of tasks and waits for their replies in >>>>>>>> the >>>>>>>> given time interval". >>>>>>>> The proposal of the new function is to return as soon as the first >>>>>>>> task finishes. >>>>>>>> >>>>>>>> For example, if we start tasks to make call to 3 different remote >>>>>>>> APIs, with different response times. >>>>>>>> >>>>>>>> API A - 50ms >>>>>>>> API B - 500ms >>>>>>>> API C - 1500ms >>>>>>>> >>>>>>>> tasks = [ >>>>>>>> Task.async(&api_a/0), >>>>>>>> Task.async(&api_b/0), >>>>>>>> Task.async(&api_c/0) >>>>>>>> ] >>>>>>>> >>>>>>>> # returns result of API A and API B waiting for 1000ms >>>>>>>> Task.yield_many(tasks, 1000) >>>>>>>> >>>>>>>> With run using `yield_many` we would wait for the 1000ms and get >>>>>>>> the responses of API A and API B. >>>>>>>> >>>>>>>> The proposal of the new function is to return as soon as we get a >>>>>>>> response. >>>>>>>> Using the same example of the 3 calls, we would wait only for 50ms >>>>>>>> (as soon as the first task finishes) and return the result of the >>>>>>>> first >>>>>>>> task finishing, without waiting for the other call. >>>>>>>> >>>>>>>> tasks = [ >>>>>>>> Task.async(&api_a/0), >>>>>>>> Task.async(&api_b/0), >>>>>>>> Task.async(&api_c/0) >>>>>>>> ] >>>>>>>> >>>>>>>> # returns only result of API A waiting for 50ms >>>>>>>> Task.proposed_function(tasks) >>>>>>>> >>>>>>>> Em quarta-feira, 31 de março de 2021 às 18:06:47 UTC-3, >>>>>>>> [email protected] escreveu: >>>>>>>> >>>>>>>>> Check out Task.yield_many/2 ( >>>>>>>>> https://hexdocs.pm/elixir/Task.html#yield_many/2) :-) >>>>>>>>> >>>>>>>>> On 31 Mar 2021, at 22:54, [email protected] < >>>>>>>>> [email protected]> wrote: >>>>>>>>> >>>>>>>>> *Proposal* >>>>>>>>> >>>>>>>>> Add a function to the Task module that takes a list of tasks, and >>>>>>>>> returns as soon as one of the tasks finishes, shuting down the other >>>>>>>>> tasks. >>>>>>>>> The behaviour would pretty similar to what Javascript have with >>>>>>>>> Promise.any >>>>>>>>> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/any >>>>>>>>> >>>>>>>>> *Motivation* >>>>>>>>> >>>>>>>>> One scenario that it could be useful is when we are integrating >>>>>>>>> with multiple APIs (providers) of the same data, and we want only the >>>>>>>>> fastest result without needing to wait for the other requests to >>>>>>>>> complete. >>>>>>>>> >>>>>>>>> Today I think this could be implemented with something similar to >>>>>>>>> the following code: >>>>>>>>> >>>>>>>>> tasks = [ >>>>>>>>> Task.async(&heavy_fun_1/0), >>>>>>>>> Task.async(&heavy_fun_2/0), >>>>>>>>> Task.async(&heavy_fun_3/0) >>>>>>>>> ] >>>>>>>>> >>>>>>>>> receive do >>>>>>>>> {ref, result} -> >>>>>>>>> tasks >>>>>>>>> |> Enum.reject(fn task -> task.ref == ref end) >>>>>>>>> |> Enum.each(&Task.shutdown/1) >>>>>>>>> >>>>>>>>> result >>>>>>>>> after >>>>>>>>> 5000 -> >>>>>>>>> {:error, :timeout} >>>>>>>>> end >>>>>>>>> >>>>>>>>> However that seems to be a common enough pattern to add to the >>>>>>>>> standard library. >>>>>>>>> >>>>>>>>> *Questions* >>>>>>>>> >>>>>>>>> - Am I missing something here and this could already be easily >>>>>>>>> accomplished with the existing API? 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