Prevent Simultaneous Workflow Executions

Feature Requests
1

Hi,

I’m trying to build a reliable logic for preventing simultaneous workflow executions to avoid duplicated run. However, when I implement the possible solutions which are mentioned in community for that, I had some troubles.

  1. Using /rest/executions-current Endpoint:

It is a good workaround to prevent simultaneous executions. However, there is a two bottleneck on this solution.

  1. Using Redis or Similar Layers
    This is also good workaround for this case. Just get and set status of workflow as ‘running’ or ‘idle’ to identify whether workflow is running already or not. This working as expected in my case but unfortunately, this is not simple as it seems. Because,

  • If the output of a node is empty, execution will stop without setting ‘idle’ of key in Redis. To overcome this, we must enable ‘Always Output Data’ option in almost every node. Then add ‘IF’ node that checks the output is empty or not, then connect it with both current flow and Redis set node.

  • If we have error workflow on a workflow, error workflow also must be configured to set status of key as ‘idle’.

Here is a sample that I trying to build:

As a result, these solutions becoming challenging. I’m thinking that it would be great if we have option on each workflow to prevent simultaneous executions.

Please type your thoughts or vote the below polling to help n8n team for prioritizing this or not.

  • I prefer trying to push limits
  • I prefer this to be built-in

0 voters

2

Yeah, the second option sounds good - although you have some extra hussle.

1 Like
3

Hey @samaritan thanks for creating this feature request, I think it makes total sense.

For the issues you mentioned, having to use Always output data is really not great but you’ve found a workaround, but for errors, there is also a possibility. You can use the Error Trigger node to handle whenever a workflow fails and also change Redis.

You can add the Error Trigger node to the same workflow you’re using and connect it to a Redis node that clears the flag.

1 Like
4

Hi,

I meant it actually, for that reason I’ve used Workflow ID for key in Redis. Here is the sample.

By the way, do you have any suggestion for ending workflows with Redis set node without using Always Output Data when nodes that don’t have output data?

1 Like
5

@samaritan unfortunately I don’t see a reason without using the Always output data flag.

6

Another approach for preventing simultaneous executions of a workflow (particularly if triggered by schedule or webhook) is to use the N8N API node to deactivate the workflow when it first starts, then reactivate itself on completion.

When a workflow execution deactivates its own workflow, its current execution continues, but further executions are prevented.

If the workflow has a lot of complexity with multiple exit points (due to errors or nodes that don’t have “Always output data”) then you can place the schedule/webhook trigger node and activate/deactivate logic in a wrapper workflow that calls the more complex workflow to do the actual work, then just wait on this one node in the wrapper workflow before re-activating the workflow (with an error handler in the wrapper as well to re-activate if so desired).