I noticed that my workflow files didn't specify what node version to use for this workflow through any node-version or node-version-file. By adding that, and upgrading my project to use node 20, this issue seems to go away.

Thank you for detailed description of the issue! We'll investigate it and come back with details.

I noticed that my workflow files didn't specify what node version to use for this workflow through any node-version or node-version-file. By adding that, and upgrading my project to use node 20, this issue seems to go away.

My workflows do always specify node-version but the post-action is slow as well.

I also have a flow log here which despite requesting lts/iron resolved 20.8.1 which isn't lts/iron. This particular setup-node use is from a reused worflow, when setup-node is used outside of a reused workflow the correct 20.9.0 is resolved.

Just want to report the same thing, from 5s -> 2m15s (Node 18)
Previous: https://github.com/specfy/stack-analyser/actions/runs/6664890448/job/18113374316
With the upgrade: https://github.com/specfy/stack-analyser/actions/runs/6664871105/job/18113316689?pr=84

Same here in multiple projects using JS with Yarn. The Post Setup Node.js job slows down from a few seconds to about 2:20 minutes after upgrading to v4.

It seems to me that this only happens when JS dependencies have been updated. Re-running the job (which causes a cache hit) is fast again - perhaps because the cache doesn't need to be saved.

My conclusion: Saving the cache is significantly slower with v4 than with v3.

Noticing this as well because I have an aggressive timeout-minutes: 1 on my actions/setup-node step, which is now causing many of my builds to fail.

I concur with @ledermann that the issue is somewhere in cache-saving.

With a cache hit, the post-action takes 0s as expected:

Without a cache hit, when trying to save the cache, the post-action times out:

See ruby/setup-ruby#543 which explains a possible cause and fix.