How to find out why cache export had failed? | Dagger | Page 1

void tapir Jan 9, 2026, 6:31 PM

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I get this error, but no explanation. I am exporting to ECR. I think I have all of the necessary push and pull permissions.

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Ah, no wait, I totally didn't think it thru. I think I need to somehow provide ECR credentials to Dagger Engine, but also JIT, as ECR has only temporary credentials.

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Or do I just need them for the Docker engine, which might be easier as there's a special provider that's available 🤔

void tapir Jan 9, 2026, 6:55 PM

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Hm, I am able to publish from the host using docker push ... but Dagger client still fails. Does Dagger client assume the credentials, or is it the Docker server? Or is there a DinD situation going on inside Dagger that it needs auth?

void tapir Jan 9, 2026, 7:30 PM

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Ok, I provided the Dagger client-side Docker config as well, just in case. But also no cigar.

void tapir Jan 9, 2026, 8:20 PM

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oh wow:

unsupported: Invalid parameter at 'ImageManifest' failed to satisfy constraint:
'Limit on number of layers per image exceeded'"

This is actually progress! The authentication worked this time:

It uploaded cache blobs for ~2 minutes (19:55:04 → 19:57:17)
Failed only when committing the manifest

Root cause: ECR has a 127-layer limit per image manifest. Dagger's cache manifest exceeds this limit.

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This is CC analysis 😄 It might be lying

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But the error is correct

digital ridge Jan 9, 2026, 8:27 PM

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one of the many reasons we're not pursuing buildkit layer export as the foundation for dagger scaleout

void tapir Jan 9, 2026, 8:53 PM

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Replaced it with S3 cache and it works. 🤷‍♂️

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ECR would have been better of course as then the layers can be reused across stages

#How to find out why cache export had failed?