• Install it with Ruby Managers like asdf or rvm
• every time you run a command use jruby -S before

Heroku recomendations from Claude

Memory Analysis

MRI Ruby (3 processes):

• Total: ~458MB (225.9 + 202.6 + 29.4)
• Multiple Ruby processes

JRuby (2 processes):

• Total: ~1,140MB (977.3 + 162.6)
• Java processes (JRuby runs on JVM)

Why JRuby Uses More Memory

1. JVM Overhead:

• Java Virtual Machine baseline: ~100-200MB
• JIT compilation cache
• Garbage collection overhead

2. JRuby Architecture:

• Compiles Ruby to Java bytecode
• Maintains both Ruby and Java object representations
• Thread-safe collections (more memory per object)

3. Different Process Model:

• MRI: Multiple processes, shared memory
• JRuby: Fewer processes, more memory per process

Optimizing JRuby Memory for Heroku

You can tune Puma configuration for JRuby. Let me check your current Puma config:

⏺ Read(config/puma.rb) ⎿ Read 35 lines (ctrl+r to

⏺ Good! Your Puma config is already optimized for JRuby:

• No workers (line 24 commented out) - JRuby uses threads, not processes
• Thread-based concurrency - More efficient for JRuby

For Heroku Production

Memory recommendations:

• 512MB dyno: Reduce RAILS_MAX_THREADS to 3-4
• 1GB dyno: Keep current settings (5 threads)
• 2GB dyno: Can increase to 8-10 threads

JRuby vs MRI Trade-offs

JRuby Advantages:

• ✅ True threading (no GIL)
• ✅ Better performance under load
• ✅ JVM ecosystem access

JRuby Trade-offs:

• ❌ Higher memory usage (~2-3x)
• ❌ Slower startup time
• ❌ Higher baseline memory

For production, monitor with: heroku logs --tail | grep "sample#memory"

Your current memory usage (1.1GB) is normal for JRuby development! 📊

I'm currently using eco dynos in heroku, can they use jruby?

⏺ Eco dynos have very limited resources that make JRuby challenging:

Eco Dyno Specs

• Memory: 512MB RAM
• CPU: Shared CPU resources
• Sleep: Apps sleep after 30 minutes of inactivity

JRuby Memory Reality Check

Your development JRuby is using ~1.1GB, but:

• Development uses 2-4x more memory than production
• Production JRuby typically needs 300-600MB minimum
• JVM baseline alone: ~150-200MB

Can Eco Handle JRuby?

Technically possible but risky:

• ✅ JRuby can run in 512MB with aggressive tuning
• ❌ Very tight memory constraints
• ❌ Risk of memory-related crashes
• ❌ Performance degradation under load

Recommendations

Option 1: Optimize for Eco (risky)

Set very conservative JVM options

heroku config:set JAVA_OPTS="-Xmx350m -Xms350m" heroku config:set RAILS_MAX_THREADS=2

Option 2: Upgrade to Basic ($7/month)

• 1GB RAM - Much safer for JRuby
• No sleep - Always available
• Better performance

Option 3: Stick with MRI Ruby on Eco

• Your MRI version (~458MB) fits comfortably
• Save JRuby migration for when you upgrade dynos

My Recommendation

For Eco dynos, stick with MRI Ruby for now. JRuby's benefits (threading, performance) aren't worth the memory constraints on Eco.

Migrate to JRuby when you're ready for Basic+ dynos!