Issue Summary

When images are initially requested via _next/image, the Cache-Control header is returned as a response header. If the CDN cache expires or is invalidated, and the image is served from the lambda /tmp file system, the default cache control headers are used.

Actual behavior

The imageOptimiser route (_next/image) only forwards the Cache-Control header from the upstream when the file is initially retrieved. When the image is subsequently served from the file system cache, the default Cache-Control value public, max-age=60 is returned.

Expected behavior

The original cache headers from the origin should be preserved, no matter the state of the file system cache.

Steps to reproduce

1. Request an image via the /_next/image endpoint, observe correct Cache-Control header in response.
2. Invalidate the /_next/image Cloudfront cache, or await cache expiry if less than lambda instance liveness (~30min).
3. Request the same image, observe Cache-Control header is now public, max-age=60

Versions

• OS/Environment: Linux/WSL 4.19.104-microsoft-standard
• @sls-next/serverless-component version: 3.7.0
• Next.js version: 12.1.0

Additional context

Checklist

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