Throttle max number of concurrent runs

The idea is:

For every job, allow the user to define a setting that limits the number of concurrent runs that the workflow accepts.

For example, say there are three workflows, A, B and C and they all call another workflow called X, where X accesses a shared resource that, for whatever reason, can/should only handle a limited load or can only be accessed by a limited number of runs at at time.

Say that for X we set this new configuration value max_concurrent_jobs=2, and then A, B and C all call X at (more or less) the same time. This should mean that X’s runs for A and B, call them Xa and Xb fire concurrently, but X’s run for C, call it Xc is queued, and will only run after Xa and Xb are done. This also means that C’s run that fired Xc just waits for Xc to finish. So:

A -> Xa
B -> Xb
C -> Xc

Then causes this:


Or if Xa finishes before Xb, then…


It should also work for concurrent calls from the same job, so if A fires three times…


My use case:

In my specific use case, I’m working with an API with a rate limit. My job already uses split and wait nodes to make going over the API’s rate limit for a single run of X less likely, but I cannot account for X being fired multiple times.

I think it would be beneficial to add this because:

This could apply to several use cases —e.g.:

  • An API with a rate limit.
  • A database with a limited thread pool.
  • Writing to a shared file.

Any resources to support this?

This would be akin to how Throttle Concurrent Builds Plugin for Jenkins works.

Are you willing to work on this?