issues with Repo.transaction + Task.async + Ecto Sandbox

[Michael Ni]

I have a Repo.transaction,

within that I have Task.async

inside the Task.async fn, since it is a separate pid

I use 

Ecto.Adapters.SQL.Sandbox.allow(repo, parent, self())

the parent is the pid where the Repo.transaction command is

My problem is all Repo calls are timing out, I think due to the Repo.transaction blocking.

1.) If I remove the first transaction and just do Task.async,  it works, proving that Sandbox allow works

2.) if I remove the Task.async and the allows, it also works as expected,

3.) when doing this in production, it works

somehow with Repo.transaction + task.async,  + mode manual, and even shared, it is not working

[Michał Muskała]

I think there was a bug related to this. Could you try updating to the newest db_connection? 

Michał.

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[Michael Ni]

I am still seeing the issue with v1.1.2 and directly master from github.

I realize this may not have to do with Sandbox, but with multiple processes within a transaction

this is a simple example to explain what is going on, i kept the essentials so the syntax may not be correct

there are two tables associated with each other,  foo and bar,       foo.bar_id  (FK)   ==     bar.id (PK)

Repo.transaction(fn ->

  case Repo.insert(foo_changeset) do

    {:ok, foo} ->

       task1 = Task.async(fn ->

           bar = build_assoc(foo)

           Repo.insert(bar)

       end

  end

end)

I'm inspecting the actual query generated in the output, 

for Repo.insert(bar), the foo_id is actually correct, however when it sends the insert to the db, it can't find it and triggers rollback

i'm getting

errors: [foobar: {"does not exist", []}],

When I remove the Task.async, it works

[José Valim]

I believe it is not about the sandbox. Transactions are per process, you cannot share a transaction across multiple process. If you have work you want to process in parallel, you can do all of the normalization on the side and leave the final step of inserting the data to the main process.

José Valim

www.plataformatec.com.br

Skype: jv.ptec

Founder and Director of R&D

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[Michael Ni]

Thanks for clearing that up

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