Asset_pipeline in heroku using the wrong asset hash for precompiled javascript

Question

I'm trying to setup my app to serve assets over the Amazon S3/Cloudfront CDN. Its a rails app and I use the asset_sync gem to achieve this as per this heroku document.

I push my project up to heroku, and then afterwards run a heroku run rake assets:precompile. This gives me output that looks like this:

    I, [2013-09-20T21:19:06.506796 #2]  INFO -- : Writing /app/public/assets/application-cb6347d3ce9380e02c37364b541fd8ae.js
I, [2013-09-20T21:19:19.979570 #2]  INFO -- : Writing /app/public/assets/application-9dc3068c1bf9290c7eb0493fd36b3587.css
[WARNING] fog: followed redirect to abc123.s3-us-west-1.amazonaws.com, connecting to the matching region will be more performant
[WARNING] fog: followed redirect to abc123.s3-us-west-1.amazonaws.com, connecting to the matching region will be more performant

Take note that the hash it writes for the JS file cb6347d3ce9380e02c37364b541fd8ae.js is correct (as I also ran this in staging under my localhost).

The problem though, is that when I hit my app on heroku and inspect the source, the JS that it is including 50460076f4c6eb614a44b6b17323efa7.js is different than the one that was compiled earlier...

Why isn't heroku picking up the right precompiled asset to use? I deployed locally and did all the same steps, my local server picks up the correct JS with no problem.

Thanks for your help!

Answer 1

After some time, I realized that this was because previously I had compiled assets locally and pushed it up. Because of this, Heroku didn't try to precompile in production and just used the old manifest.json that was previously checked in.

You can either recompile locally and push it up, or run rake assets:clobber to delete all precompiled assets, then commit/push and heroku will realize that it needs to precompile. Afterwards, it should be using the correct manifest file and assets should show as normal.

I found this blog post really useful in understanding the situation: http://www.rubycoloredglasses.com/2013/08/precompiling-rails4-assets-when-deploying-to-heroku/