CI 429 Too Many Requests (Rate Limit)

A 429 means the upstream throttled the request, you exceeded its rate limit. It is transient and retryable: backing off, or authenticating for a higher limit, clears it.

What this error means

An install or pull fails with 429 Too Many Requests (e.g. Docker Hub anonymous limits). Waiting and retrying, or authenticating, succeeds with no change to the request.

Error response from daemon: toomanyrequests: You have reached your pull rate limit.
##[error] 429 Too Many Requests

Common causes

Anonymous or shared-IP rate limits

Unauthenticated pulls from a shared CI IP hit per-IP limits quickly (Docker Hub is a common case).

A burst of requests in a short window

Highly parallel jobs hammering one API can trip its rate limiter.

How to fix it

Back off and respect Retry-After

Honor the throttle and retry after the indicated delay.

for i in 1 2 3 4 5; do
  curl -fsSL "$URL" -o out && break
  sleep $((i*15))
done

Authenticate and cache

1. Log in to the registry to get a higher rate limit.
2. Use a pull-through cache/mirror for images.
3. Cache dependencies so repeat runs do not re-fetch.

How to prevent it

• Authenticate to registries in CI.
• Cache images and dependencies.
• On managed runners, transient 429 throttling is detected and the job is automatically retried with backoff, so a one-off rate limit does not fail the build.

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