Codestin Search App

rhysperry111 · 2026-06-18T16:14:12Z

What type of PR is this?

/kind bug

What this PR does / Why we need it:

There is an issue caused by inconsistencies in FleetAutoscaler upscale logic and downscale logic, resulting in flapping when using a List based policy. This was reported here on Slack.

The root cause of the problem is due to the way that downscale decisions are made. The downscale logic:

Gets the list of current GameServers
Simulates a deletion
Checks whether doing such would cause a server to need to be added again according to the list policy

The first two steps were implemented in a way that does not match how Fleets will actually choose to delete a server, as it doesn't exclude GameServers that would normally be considered undeletable. This inconsistency between the simulated deletion and actual deletion logic is what leads to constant upscaling and downscaling (flapping).

The first commit on this PR implements a test to reproduce the issue described, and to help check for regressions in the future.

The second commit on the PR implements the logic in FleetAutoscaler to correctly check which servers would be deleted on a downscale.

Which issue(s) this PR fixes:

Addresses the issue raised on Slack here.

Did you use AI tools in preparing this PR?:

No

Special notes for your reviewer:

A build of this code was tested by the user that originally reported the issue on Slack. They are able to confirm that it fixes the original issue.

markmandel · 2026-06-18T18:34:43Z

/gcbrun

Let's run it!

agones-bot · 2026-06-18T19:33:58Z

Build Succeeded 🥳

Build Id: dba2d045-e0fb-411c-80bf-d65f08fb8fde

The following development artifacts have been built, and will exist for the next 30 days:

image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.59.0-dev-54051dd
image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.59.0-dev-54051dd
image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.59.0-dev-54051dd-linux
image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.59.0-dev-54051dd
image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.59.0-dev-54051dd
image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.59.0-dev-54051dd
Linux C++ SDK (build): agonessdk-1.59.0-dev-54051dd-linux-arch_64.tar.gz
SDK Server: agonessdk-server-1.59.0-dev-54051dd.zip

A preview of the website (the last 30 builds are retained):

https://54051dd-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4625/head:pr_4625 && git checkout pr_4625
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.59.0-dev-54051dd

markmandel · 2026-06-19T21:39:19Z

/gcbrun

agones-bot · 2026-06-19T22:56:33Z

Build Failed 😭

Build Id: 25f74ba2-9d6d-4ce8-8b13-722ed7a854e3

Status: FAILURE

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

rhysperry111 · 2026-06-19T23:02:26Z

It passed yesterday and all that's changed since is a rebase and a comment 😭

markmandel · 2026-06-19T23:44:57Z

/gcbrun

That's a new flake - haven't seen that before. Let's run it again, while I run this in the background.

agones-bot · 2026-06-20T00:41:51Z

Build Succeeded 🥳

Build Id: 4e13082e-de99-44a5-ab21-40bf3e84d636

The following development artifacts have been built, and will exist for the next 30 days:

image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.59.0-dev-f4f142d
image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.59.0-dev-f4f142d
image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.59.0-dev-f4f142d-linux
image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.59.0-dev-f4f142d
image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.59.0-dev-f4f142d
image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.59.0-dev-f4f142d
Linux C++ SDK (build): agonessdk-1.59.0-dev-f4f142d-linux-arch_64.tar.gz
SDK Server: agonessdk-server-1.59.0-dev-f4f142d.zip

A preview of the website (the last 30 builds are retained):

https://f4f142d-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4625/head:pr_4625 && git checkout pr_4625
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.59.0-dev-f4f142d

lacroixthomas

LGTM

markmandel

Found a couple of small things - but otherwise, LGTM.

Signed-off-by: Rhys Perry <[email protected]>

…ules Signed-off-by: Rhys Perry <[email protected]>

rhysperry111 · 2026-06-23T18:12:39Z

Reworked the tests to be a bit more data-driven (with some test cases that also hit the limited paths). Also covers asserting the limited response. Thanks Mark and Thomas for the pointers :D

markmandel · 2026-06-23T18:22:11Z

/gcbrun

agones-bot · 2026-06-23T19:19:42Z

Build Failed 😭

Build Id: 1fc4aa37-0b38-445a-a757-60505f6aa9f2

Status: FAILURE

To get permission to view the Cloud Build view, join the agones-discuss Google Group.

markmandel · 2026-06-23T20:07:47Z

/gcbrun

agones-bot · 2026-06-23T21:08:50Z

Build Succeeded 🥳

Build Id: 51d5bc32-aa28-4464-afbe-8f6c998ebd63

The following development artifacts have been built, and will exist for the next 30 days:

image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.59.0-dev-5cbf6d1
image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.59.0-dev-5cbf6d1
image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.59.0-dev-5cbf6d1-linux
image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.59.0-dev-5cbf6d1
image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.59.0-dev-5cbf6d1
image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.59.0-dev-5cbf6d1
Linux C++ SDK (build): agonessdk-1.59.0-dev-5cbf6d1-linux-arch_64.tar.gz
SDK Server: agonessdk-server-1.59.0-dev-5cbf6d1.zip

A preview of the website (the last 30 builds are retained):

https://5cbf6d1-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4625/head:pr_4625 && git checkout pr_4625
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.59.0-dev-5cbf6d1

rhysperry111 · 2026-06-23T21:11:01Z

Yippee!

github-actions Bot added kind/bug These are bugs. size/M labels Jun 18, 2026

rhysperry111 force-pushed the fix/fleetautoscaler-list-flapping branch 2 times, most recently from d6a0d4d to 54051dd Compare June 18, 2026 16:31

rhysperry111 marked this pull request as ready for review June 18, 2026 20:05

lacroixthomas reviewed Jun 18, 2026

View reviewed changes

Comment thread pkg/fleetautoscalers/fleetautoscalers.go Outdated

rhysperry111 force-pushed the fix/fleetautoscaler-list-flapping branch 3 times, most recently from 7689469 to f4f142d Compare June 19, 2026 21:37

rhysperry111 requested a review from lacroixthomas June 22, 2026 17:06

lacroixthomas approved these changes Jun 22, 2026

View reviewed changes

markmandel reviewed Jun 23, 2026

View reviewed changes

Comment thread pkg/fleetautoscalers/fleetautoscalers_test.go

Comment thread pkg/fleetautoscalers/fleetautoscalers_test.go Outdated

Comment thread pkg/fleetautoscalers/fleetautoscalers_test.go Outdated

rhysperry111 added 2 commits June 23, 2026 19:09

test: reproduce fleetautoscaler flapping bug

577ba71

Signed-off-by: Rhys Perry <[email protected]>

fix: ensure that fleetautoscaler gameserver sorting obeys deletable r…

5cbf6d1

…ules Signed-off-by: Rhys Perry <[email protected]>

rhysperry111 force-pushed the fix/fleetautoscaler-list-flapping branch from ca6e052 to 5cbf6d1 Compare June 23, 2026 18:11

rhysperry111 requested a review from markmandel June 23, 2026 18:13

markmandel approved these changes Jun 23, 2026

View reviewed changes

markmandel enabled auto-merge (squash) June 23, 2026 18:22

markmandel merged commit d1bec35 into agones-dev:main Jun 23, 2026
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