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fix(ci): spend the whole preload budget retrying a throttled pull - #2496
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…ll failed The preload landed in #2480 and the next KWOK run on that commit failed identically. The retry was the wrong shape, not the wrong idea. Measured from the failing job: three attempts at 02:20:42, 02:20:49 and 02:20:59, each pull failing in about a second against a fixed 5s/10s backoff. The function gave up 17 seconds in while holding a 180 second budget -- roughly 163 seconds unused. Against a per-IP registry throttle that is close to the worst possible schedule: fast enough to stay inside the same throttle window, then stopping long before it would reset. It is a throttle, not an outage: 125 of the 127 concurrent matrix jobs in that same run pulled the same image successfully at the same moment. Retry until the budget is spent, with backoff doubling from 5s and capped at 30s so a long budget waits rather than hammers. Also forward docker's stderr and log it when the budget runs out. The original fix discarded it, so diagnosing #2483 needed a manual investigation that the log should have answered -- the retry landed in #2480, the diagnosis did not. Fixes: #2483 Signed-off-by: Mark Chmarny <mark@chmarny.com>
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Included review availability: Your plan provides up to 12 included reviews per hour; 10 remain after this review. 📝 WalkthroughWalkthroughThe preload script adds configurable exponential backoff. Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This CI-only change expands retrying within the existing bounded preload timeout and preserves the fallback behavior; the remaining test concern is minor and non-blocking, so no actionable merge-blocking risk remains. Suggested reviewers: 🚥 Pre-merge checks | ✅ 3 | ❌ 1❌ Failed checks (1 warning)
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Inline comments:
In `@kwok/scripts/lib/preload-image.sh`:
- Line 169: Update the preload loop around preload_remaining so that when it
fails after a docker pull consumes the remaining budget, pull_err is logged
before breaking and later cleanup removes it. Add coverage for a failed pull
that exhausts the full budget, verifying Docker’s stderr appears in the warning.
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Review found a pull that consumes the last of the budget loses its own error: that path breaks out of the backoff clamp, skipping the branch that logged the cause, and the temp file is deleted before the fallback warning runs. Rather than add the log line to that branch, remove the class. The loop has four exits -- image already cached, budget spent before an attempt, pull succeeded, budget spent after a failed attempt -- and the previous version reported on exactly one of them. Capture the cause into a variable the moment a pull fails, so it survives every later exit, and report it from a single site after the loop. This is the third fix in this function that was complete on one path and not another (bounded pull but not inspect, bounded calls but not the backoff sleep, now reporting on one exit of four). One site that all paths flow through is what stops the pattern. Adds a case for a failed pull that spends the whole budget itself, which is a different loop exit from the existing budget-exhausted case. Removing the capture fails three cases. Signed-off-by: Mark Chmarny <mark@chmarny.com>
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Both findings addressed. Reviewed SHA 1. Deadline exhaustion drops Docker stderr — already fixed at headCodeRabbit found the same path and it was fixed in Not as a patch to that branch. The loop has four exits — image already cached, budget spent before an attempt, pull succeeded, budget spent after a failed attempt — and the previous version reported the cause on exactly one. The error is now captured into The regression test you asked for is 2.
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Summary
Make the KWOK image preload retry until its budget is spent instead of giving up after three attempts in ~17 seconds, and log why a pull failed.
Motivation / Context
#2480 landed the preload and the very next KWOK run on the merge commit failed identically. The retry was the wrong shape, not the wrong idea.
It is a throttle, not an outage. In run 33350102144 (on
dab6f8150, which contains the preload):125 jobs pulled
public.ecr.aws/docker/library/registry:3.1.1successfully at the same moment from the same runner pool. That rules out an outage, a bad pin, and a broken image. The manifest also fetches withHTTP 200from a workstation. What is left is per-IP throttling under a 127-job concurrent matrix — which also explains the 2026-08-30 streak, where a different lane failed each run.The retry schedule was close to worst-case for that. From the failing job:
Each pull failed in about a second; the backoff was a fixed 5s then 10s. All three attempts finished inside 17 seconds and the function gave up with ~163 seconds of its own budget unused — retrying fast enough to stay inside the same throttle window, then stopping long before it would reset.
Related: #2483, #2480, #843
Deliberately linked as
Related, not as a closing reference. This narrows the failure window; it does not meet that issue's acceptance criteria, which require that a KWOK run not depend on an unauthenticated third-party registry pull at job time, and several consecutive green KWOK runs onmainto confirm. Neither holds here — the pull dependency is unchanged, and one run proves nothing about an intermittent 1-in-127 failure. #2483 stays open for the caching/mirroring work.Type of Change
Component(s) Affected
cmd/aicr,pkg/cli)cmd/aicrd,pkg/server)pkg/recipe)pkg/bundler,pkg/component/*)pkg/collector,pkg/snapshotter)pkg/validator)pkg/errors,pkg/k8s)docs/,examples/)kwok/scripts/libImplementation Notes
Retry until
preload_remainingreports the budget spent, with backoff doubling from 5s and capped at 30s. The cap matters: an uncapped double would spend a long budget on one enormous sleep and leave no attempt near the end of the window.The bounded-budget work from #2480 is unchanged — every
docker/kindcall is still undertimeout, and the backoff is still clamped so the function cannot outlive its deadline. Only the attempt schedule changes.Second fix: forward
docker's stderr. The original useddocker pull --quiet ... >/dev/null 2>&1, discarding the cause. That is why diagnosing #2483 took a manual investigation the log should have answered — the retry landed in #2480, the diagnosis did not. The cause is now captured and logged when the budget runs out.Not doing here: caching the image (
actions/cache+docker save/load), mirroring to GHCR, or authenticating to ECR. All are heavier, and with 125/127 pulls already succeeding the tail is the problem rather than the dependency. #2483 stays open and records them — which is why this PR does not claim to fix it.Testing
Two new cases, both mutation-verified:
retry-count-follows-the-budget,budget-allows-more-than-three-attempts(2 failures)docker's stderr againpull-exhausted-reports-the-errorThe second needed two passes and is worth calling out. My first version asserted the string
"last error"appeared — which is logged even when the captured stderr is empty, so the mutation passed. It now asserts the actual cause (toomanyrequests) reaches the log.Risk Assessment
Rollout notes: CI-only; no product code. Worst case a throttled pull now occupies up to its 180s budget before falling back to the kubelet, instead of 17s — bounded, and the fallback is unchanged.
Checklist
make testwith-race) — N/A, no Go changesmake lint)git commit -S)