Sunday, August 13, 2017

versioning js and css with gulp-rev and gulp-revReplace

I've discussed before how I run on S3, but one issue I did not address was how to version updates, so that each visitor loads a consistent set of assets. Here's the problem.

  • on Monday I publish v1 assets to the S3 bucket behind
  • later on Monday Fred visits, and his browser caches several v1 javascript and CSS files - a.js, b.js, x.css, y.css, ...
  • on Tuesday I publish v2 assets to S3 - just changing a few files
  • on Wednesday Fred visits, but for whatever reason his browser cache updates b.js to v2, but loads v1 of the other assets from cache

On Wednesday Fred loads an inconsistent set of assets that might not work together. There are several approaches people take to avoid this problem. Surma gave a good overview of HTTP cache headers and thinking in this talk on YouTube, and Jake Archibald goes into more detail in this bLog (we set cache-headers directly on our S3 objects).

Long story short - I finally wired up my gulpfile with gulp-rev and gulp-rev-replace to add a hash to the javascript and css file names. Each visitor to is now guaranteed to load a consistent set of assets, because an asset's name changes when its content changes. I was really happy to find gulp-rev - it just takes care of things for me. The only gotcha is that gulp-rev-rewrite does not like to work with relative asset paths (ex - <script src="511.js"), so I had to update a few files to use absolute paths (src="/511/511.js") - otherwise things worked great.

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