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Improve shutdown logic: Wait until no requests are made #12397

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Improve shutdown logic: Wait until no requests are made #12397

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motoki317
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@motoki317 motoki317 commented Nov 21, 2024 •
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What this PR does / why we need it:

Hello!
This PR mainly introduces 3 changes:

  • Improves shutdown logic of the controller.
    • The controller now waits until no more requests are seen to the nginx process before exiting. This is done by polling /nginx_status (stub_status) page, and see if the requests handled number goes up.
    • resolves Zero downtime upgrade #6928.
  • Changes the grace-shutdown-period in chart values to a more reasonable default.
    • Kubernetes pods are terminated (sent a SIGTERM) and removed from Service endpoints in parallel, so pods are expected to wait a bit before stopping to accept new connections from the upstream - this is the very reason this PR exists. It is generally a good idea in Kubernetes to wait a little bit after receiving a SIGTERM signal before exiting - I have changed the default wait time from 0s to 10s.
    • resolves Zero downtime upgrade #6928 along with the above change.
  • Removes the unnecessary (verbose) wait-shutdown binary and preStop hook.

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • CVE Report (Scanner found CVE and adding report)
  • Breaking change (fix or feature that would cause existing functionality to change)
    • I should note that: this PR technically introduces a breaking change to the default configuration values, but shouldn't be much of a problem to the users.
  • Documentation only

Which issue/s this PR fixes

fixes #6928
fixes #6287

How Has This Been Tested?

Checklist:

  • My change requires a change to the documentation.
  • I have updated the documentation accordingly.
  • I've read the CONTRIBUTION guide
  • I have added unit and/or e2e tests to cover my changes.
  • All new and existing tests passed.

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linux-foundation-easycla bot commented Nov 21, 2024 •
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CLA Signed

The committers listed above are authorized under a signed CLA.

@k8s-ci-robot k8s-ci-robot added cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. area/helm Issues or PRs related to helm charts labels Nov 21, 2024
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This issue is currently awaiting triage.

If Ingress contributors determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

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Welcome @motoki317!

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@k8s-ci-robot k8s-ci-robot added the needs-kind Indicates a PR lacks a `kind/foo` label and requires one. label Nov 21, 2024
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Hi @motoki317. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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@k8s-ci-robot k8s-ci-robot added needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. needs-priority labels Nov 21, 2024
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✅ Deploy Preview for kubernetes-ingress-nginx canceled.

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🔨 Latest commit ae42b6a
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@k8s-ci-robot k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. and removed cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Nov 21, 2024
@motoki317 motoki317 force-pushed the feat/improve-pod-shutdown branch 2 times, most recently from 668e84e to 60f8c04 Compare November 21, 2024 13:21
@longwuyuan longwuyuan mentioned this pull request Nov 21, 2024
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/ok-to-test

@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Nov 22, 2024
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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: motoki317
Once this PR has been reviewed and has the lgtm label, please ask for approval from rikatz. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

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Gacko
Gacko requested changes Nov 24, 2024
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Please do not change the manifests in deploy/static/. This is part of the release process.

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@Gacko I see, I've reverted the changes there.

@k8s-ci-robot k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Nov 28, 2024
@motoki317
refactor: Extract out stub_status scraper for external use
e76ea47
@motoki317
Improve shutdown logic: wait until no requests are made
25f5d09 
Pods in Kubernetes endpoints are expected to shut-down 'gracefully' after receiving SIGTERM -
we should keep accepting new connections for a while. This is because Kubernetes updates Service endpoints
and sends SIGTERM to pods *in parallel*.

See kubernetes/kubernetes#106476 for more detail.
@motoki317
Make shutdown grace periods to more reasonable defaults
3fe18f1 
Note that post-shutdown-grace-period doesn't seem to contribute to graceful shutdown,
see kubernetes#8095 for discussion.
@motoki317
refactor: wait-shutdown preStop hook is not necessary
ff45a2a 
/wait-shutdown preStop script's only job is to send SIGTERM to nginx-ingress-controller,
which is PID 1, so it's the same with or without in Kubernetes environments.

See kubernetes#6287 for discussion.
@motoki317
Fix lint issues
872d64b
@motoki317
fix: Add failure threshold to graceful shutdown
4f43d4a
@motoki317
fix: We do not need to account for readinessProbe requests
ae42b6a 
since the probe is handled within ingress-nginx-controller and
does not reach nginx process.
@k8s-ci-robot k8s-ci-robot removed the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Nov 28, 2024
@motoki317
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Hi, I'm wondering what's the status of this PR.
Is this being discussed or reviewed,
or should I be a bit more patient and wait?

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longwuyuan commented Nov 29, 2024 via email

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@Gacko Gacko Gacko requested changes

@rikatz rikatz Awaiting requested review from rikatz

@ubergesundheit ubergesundheit Awaiting requested review from ubergesundheit

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Zero downtime upgrade Distinguish wait-shutdown command from standard k8s SIGTERM
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@motoki317 @k8s-ci-robot @adrianmoisey @longwuyuan @Gacko @rikatz