Unique Workflows (no overlap per user)

Special Sections Oban
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1

I have an Oban Workflow that I want to limit so that only 1 Workflow will run for a user at a time, but not block for other users.

From the config it looks like I can do this per worker, but my workflow could have concurrent workers.

I don’t know if there is a way to do this with Oban config

help!

Any ideas?

2

Depending in the users amount, I would use a GenServer per user, saving in the state the jobs queue and a tick function wich take the first in the list, execute and update the state…

If you want to persist the state in case of crashes and you are not using a cluster, you can save the state in ETS… and load it again in the init callback.

If you are using a cluster, you can use Horde and recover the state with :continue flag.

I’m not sure if I would use Oban for this case…

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3

it’s an Oban Workflow that I am trying to run uniquely

4

Yes! Indeed, there is. With Pro v1.6 you can set a global partition by workflow_name or some other unique attribute of that users workflow. (That’s really up to you). It’s more about concurrency and not uniqueness.

config :my_app, Oban,
  queues: [
    queue_name: [limit: 20, global_limit: [allowed: 1, partition: [meta: :workflow_name]]]
  ]

In this case, each node can run up to 20 jobs but only 1 of that particular workflow. It relies on you setting a distinct workflow name for each user.

Workflow.new(workflow_name: "some-workflow-#{user_id}")
4 Likes
5

Nice! Is 1.6 ready for prod use yet?

Just reading 1.6 docs now.

Can I use the new context in the partition?

e.g.

global_limit: [allowed: 1, partition: [meta: :workflow_name, context: :user_id]]

*edit: looks like no. workflow_name will work, though. thanks

6

Worker name or workflow name? :thinking:

7

yeah workflow_name :sweat_smile:

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8

We run it in production. It’s in rc for a while, at least a month. Totally up to you.

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