Concurrent::Promise.all? always returns nil

[shaggyone]

Concurrent::Promise.all?(
 Concurrent::Promise.execute { 2 },
 Concurrent::Promise.execute { 3 }
).execute.value
=> nil

Expected value is true

[jdantonio]

That's not how the #all? method works. The aggregation methods don't return a value, they execute a chained handler method based on the aggregate success or failure.

This success case:

Concurrent::Promise.all?(
 Concurrent::Promise.new { 2 },
 Concurrent::Promise.new { 3 }
).then{ puts "Succeeded" }.
  rescue{ |reason| puts "Failed with #{reason}" }.execute

will output "Succeeded" to the console.

This failure case:

Concurrent::Promise.all?(
 Concurrent::Promise.new { raise StandardError },
 Concurrent::Promise.new { 3 }
).then{ puts "Succeeded" }.
  rescue{ |reason| puts "Failed with #{reason}" }.execute

will output "Failed with Concurrent::PromiseExecutionError" to the console.

The original conversations about this API and why they work this way can be found here and here.

[tomascharad]

HI @jdantonio ,

The javascript implementation of Promise.all does actually return an array with the results of each fulfilled promise, if you don't provide this array, the promise.all function is almost useless IMHO.

[pitr-ch]

Yeah i've missed that completely in the old discussions about this API. I assumed it passes the values to the block. I agree it limits the usability. New implementation of promises which is almost ready, just API renaming in progress, passes the values as expected.

[tomascharad]

Thanks @pitr-ch ,

Is there any way to try that alpha version?

[pitr-ch]

it is available in concurrent-ruby-edge see http://ruby-concurrency.github.io/concurrent-ruby/Concurrent/Edge/FutureShortcuts.html for documentation. But please be warned that even though the internals will stay the same, the names and namespace will be changing in the next release. If you have feedback about the new implementation we will appreciate it.

If you wish to live beyond edge you can try #522 :)

[tomascharad]

Many thanks @pitr-ch , I'll try that tomorrow and will let you know.

[tomascharad]

Hi @pitr-ch ,

I just updated to:

# TCT: Concurrency
gem 'concurrent-ruby', '~> 1.0.3.pre3'
gem 'concurrent-ruby-edge', '~> 0.2.3.pre3'

But Concurrent::Promise.all?still doesn't seem to return the responses.
I'm doing:

promises = attachments_with_content.map do |attachment|
  promise = Concurrent::Promise.new{
    pdf = foliator.foliate(attachment.content.url, attachment.initial_folio, Date.new.to_s, false, false, 0)
    pdf
  }.execute
  promise
end

all_promises = Concurrent::Promise.all?(*promises)
all_promises.then{ |responses|
  puts 'Here!'
  puts 'Hereaaaa!'
  puts responses
  ...
end
sleep(15)
puts puts all_promises.state

And my console just prints

Here!
Hereaaaa!

fulfilled

[tomascharad]

Hi @pitr-ch ,

I also tried using:

gem 'concurrent-ruby', :git => "git@github.com:pitr-ch/concurrent-ruby.git", :branch => "futures"

Without the edge gem and requiring

require 'concurrent'

But the responses object still seems to be null:

Here!
Hereaaaa!

fulfilled

[pitr-ch]

Ah, the old Promise implementation. is still used in your example. The new promises are created differently, please have look at the documentation which was linked earlier. Requiring the edge does not change the old API.