React/Rails项目中如何缩减Rails Slug体积？

Hey there! Let’s tackle your question step by step.

Is a 108.9MB Ruby side slug normal? #

Short answer: No, that’s definitely larger than expected for a Ruby app with just models and controllers. Ruby code itself is lightweight—most of that bulk is almost certainly coming from your gem dependencies, their compiled extensions, or unnecessary files bundled with the gems. Even with production gems, a typical lean Ruby API might sit around 30-50MB at most, so 108MB is a red flag that there’s room to trim.

How to reduce your Ruby slug size #

Here are practical steps to cut down that bulk:

• Double-check production-only gem installation
  Make sure you’re only installing gems needed for production. Run bundle install --without development test locally to verify, and confirm your Gemfile groups are set up correctly. Heroku should automatically respect this, but it’s worth double-checking that no dev/test gems are slipping into production.

• Enable gem cleanup via the Ruby Buildpack
  The Heroku Ruby Buildpack has a built-in cleanup feature that removes non-essential files (like gem documentation, test suites, and example files) from the vendor/bundle directory. Enable it by setting this config var:

  heroku config:set BUILDPACK_RUBY_CLEAN=true
  

  This can shave off a surprising amount of space—many gems include megabytes of docs you’ll never need in production.

• Analyze your slug’s breakdown
  To find exactly what’s taking up space, run these commands via Heroku CLI:

  heroku run bash
  # Once in the dyno shell, check directory sizes
  du -h --max-depth=1 /app
  # Drill into vendor/bundle to spot large gems
  du -h --max-depth=2 /app/vendor/bundle
  

  This will show you which gems or directories are the biggest culprits. For example, gems with native extensions (like nokogiri, pg, or redis) can have large compiled binaries—if you don’t need a specific feature of a gem, see if there’s a lighter alternative.

• Remove unused gem dependencies
  Even if you think you’ve removed all unnecessary gems, do a deep dive: check Gemfile.lock for transitive dependencies you didn’t explicitly add. Use bundle why <gem-name> to see why a gem is included, and if it’s not critical, remove the parent gem that pulls it in.

• Use heroku slug:analyze for official insights
  Heroku has a built-in tool to break down your slug’s size by file/directory. Run:

  heroku slug:analyze
  

  This will give you a structured report of what’s contributing to the bulk, which is super helpful for targeting cleanup.

Relevant documentation notes #

Heroku’s official Ruby Buildpack documentation covers all these optimization steps, including gem cleanup, production gem management, and slug analysis. You can access these guides directly via the Heroku Dashboard’s app documentation or by running heroku help buildpacks for CLI-related info.

内容的提问来源于stack exchange，提问作者Jay