fix: delay upstream DNS resolution to prevent nginx startup failures#2718
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peace-maker merged 1 commit intoGallopsled:devfrom Apr 19, 2026
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Use nginx variable pattern (set $upstream + proxy_pass https://$upstream) to defer DNS resolution until first request instead of at config parse time. This fixes the occasional 'host not found in upstream' error in CI when nginx container starts before Docker DNS is fully available. Fixes Gallopsled#2712
peace-maker
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Apr 19, 2026
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Thank you. There was another PR for this problem very recently :D #2715 that came to the same solution, but has implementation problems. It seems there's some interest in pointing agents at this repo.
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Summary
The nginx cache proxy fails to start in CI with the error:
This happens because nginx resolves upstream domains at config parse time,
but Docker's embedded DNS (127.0.0.11) may not be fully available when
the container starts.
Solution
Changed all
proxy_passdirectives from:To use the variable pattern:
This defers DNS resolution to the first request, when Docker DNS is guaranteed
to be available.
Testing
The change can be verified by running:
Fixes
Fixes #2712