Compress wasm files for upload

[rossta]

We observed that Amazon Cloudfront was not compressing the Rails WASM download so that the browser was having to transfer 130MB. Chrome was also not caching the file on disk for subsequent page loads.

We first added Cache-Control header for the upload to S3 after removing the previous uploads in #5.

We then updated the S3 bucket CORS policy to include allow all request headers to satisfy the Cloudfront compressed files requirement that the Origin include the Content-Length header.

• Cloudfront docs: Serving Compressed Files
• S3 docs: Managing CORS

We also learned that the Rails WASM upload is too large to be compressed by Cloudfront, per the Cloudfront docs:

CloudFront compresses objects that are between 1,000 bytes and 10,000,000 bytes in size

From a StackOverflow answer, we also learned that we could compress eagerly and set the Content-Encoding header on the upload.

• How to manually gzip files for web and Amazon CloudFront(https://stackoverflow.com/questions/51033550/how-to-manually-gzip-files-for-web-and-amazon-cloudfront)

We experimented with different brotli compression levels, i.e. brotli -q <1-11> and settled on level 8 compression as a good tradeoff between final compressed size and compression execution time:

For brotli -q <LEVEL> rails-7.1-ruby-3.3-web.wasm

• LEVEL=4 time: 01.5s, size: 41M
• LEVEL=6 time: 03.8s, size: 37M
• LEVEL=8 time: 10.8s, size: 36M
• LEVEL=9 time: 43.0s, size: 35M
• LEVEL=10 time: 3m, size: 33M
• LEVEL=11 time: 9m, size: 30M

We also looked at using the WebAssembly Binaryen wasm-opt utility as an optimization step but decided to omit as the step only reduced a small % of size while adding several minutes to the build.