swift test is hanging on GitHub Actions, started in Swift 6.0+

[czechboy0]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

swift test is hanging on GitHub Actions, started in Swift 6.0+

Example: https://github.com/apple/swift-distributed-actors/actions/runs/13964630089/job/39092176843

GHA cancels the job after 6 hours.

Expected behavior

swift test would continue to building and running tests.

Actual behavior

swift test hangs after cloning, before building.

Steps to reproduce

I haven't been able to reproduce locally, but happens frequently on this CI job: https://github.com/apple/swift-distributed-actors/actions/runs/13964630089/job/39092176843

Swift Package Manager version/commit hash

6.0 and newer, doesn't reproduce on 5.9/5.10

Swift & OS version (output of swift --version ; uname -a)

swift:6.0-jammy container

[dschaefer2]

Given you can't reproduce this locally, I'm wondering if you're just running out of memory in the jobs. I've seen that make it appear to be hanging when, for example, running an a VM with 2GB or less. Mind you that usually manifests itself in the compiler, especially building swift-syntax.

[czechboy0]

@rnro do you know if that's something we can change?

[rnro]

We are using the standard hosted GitHub runners which have 16 GB of RAM and running the Swift test jobs within a docker container.

Running free -h inside those docker containers (before any test activity has started) prints:

               total        used        free      shared  buff/cache   available
Mem:            15Gi       913Mi       6.3Gi        64Mi       8.4Gi        14Gi
Swap:          4.0Gi          0B       4.0Gi

So I don't think memory pressure should be an issue.

[dschaefer2]

@rnro Yes, that should be lots. Hard pressed to understand what's happening on those machines.

[czechboy0]

Any extra logging we can enable to help diagnose this?

[dschaefer2]

You could always add --vv to the swift build command.