Month: April 2025

Introduction

Performance optimization is critical for delivering fast, responsive Rails applications. This comprehensive guide covers the most important profiling tools you should implement in your Rails 8 application, complete with setup instructions and practical examples.

Why Profiling Matters

Before diving into tools, let’s understand why profiling is essential:

1. Identify bottlenecks: Pinpoint exactly which parts of your application are slowing things down
2. Optimize resource usage: Reduce memory consumption and CPU usage
3. Improve user experience: Faster response times lead to happier users
4. Reduce infrastructure costs: Efficient applications require fewer server resources

Essential Profiling Tools for Rails 8

1. Rack MiniProfiler

What it does: Provides real-time profiling of your application’s performance directly in your browser.

Why it’s important: It’s the quickest way to see performance metrics without leaving your development environment.

Installation:

# Gemfile
gem 'rack-mini-profiler', group: :development

Usage example:
After installation, it automatically appears in your browser’s corner showing:

• SQL query times
• Ruby execution time
• Memory allocation
• Flamegraphs (with additional setup)

Advantages:

• No configuration needed for basic setup
• Shows N+1 query warnings
• Integrates with Rails out of the box

GitHub: https://github.com/MiniProfiler/rack-mini-profiler
Documentation: https://miniprofiler.com/

2. Bullet

What it does: Detects N+1 queries, unused eager loading, and missing counter caches.

Why it’s important: N+1 queries are among the most common performance issues in Rails applications.

Installation:

# Gemfile
gem 'bullet', group: :development

Configuration:

# config/environments/development.rb
config.after_initialize do
  Bullet.enable = true
  Bullet.alert = true
  Bullet.bullet_logger = true
  Bullet.console = true
  Bullet.rails_logger = true
end

Example output:

GET /posts
USE eager loading detected
  Post => [:comments]
  Add to your query: Post.includes([:comments])

Advantages:

• Catches common ORM performance issues early
• Provides specific recommendations for fixes
• Works across all environments

GitHub: https://github.com/flyerhzm/bullet
Documentation: https://github.com/flyerhzm/bullet/blob/master/README.md

3. Ruby Prof (and StackProf)

What it does: Low-level Ruby code profiler that shows exactly where time is being spent.

Why it’s important: When you need deep insight into method-level performance characteristics.

Installation:

# Gemfile
gem 'ruby-prof', group: :development
gem 'stackprof', group: :development

Usage example:

# In your controller or service object
result = RubyProf.profile do
  # Code you want to profile
end

printer = RubyProf::GraphPrinter.new(result)
printer.print(STDOUT, {})

For StackProf:

StackProf.run(mode: :cpu, out: 'tmp/stackprof.dump') do
  # Code to profile
end

Advantages:

• Method-level granularity
• Multiple output formats (call graphs, flamegraphs)
• StackProf is sampling-based so has lower overhead

GitHub: https://github.com/ruby-prof/ruby-prof
Documentation: https://github.com/ruby-prof/ruby-prof/blob/master/README.md

StackProf Alternative:
GitHub: https://github.com/tmm1/stackprof
Documentation: https://github.com/tmm1/stackprof/blob/master/README.md

4. Memory Profiler

What it does: Tracks memory allocations and helps identify memory bloat.

Why it’s important: Memory issues can lead to slow performance and even crashes.

Installation:

# Gemfile
gem 'memory_profiler', group: :development

Usage example:

report = MemoryProfiler.report do
  # Code to profile
end

report.pretty_print(to_file: 'memory_report.txt')

Advantages:

• Shows allocated objects by class and location
• Tracks retained memory after GC
• Helps find memory leaks

GitHub: https://github.com/SamSaffron/memory_profiler
Documentation: https://github.com/SamSaffron/memory_profiler/blob/master/README.md

5. Skylight

What it does: Production-grade application performance monitoring (APM).

Why it’s important: Understanding real-world performance characteristics is different from development profiling.

Installation:

# Gemfile
gem 'skylight'

Configuration:

# config/skylight.yml
production:
  authentication: [YOUR_AUTH_TOKEN]

Advantages:

• Low-overhead production profiling
• Endpoint-level performance breakdowns
• Database query analysis
• Exception tracking

Website: https://www.skylight.io
Documentation: https://docs.skylight.io
GitHub: https://github.com/skylightio/skylight-ruby

6. AppSignal

What it does: Full-stack performance monitoring and error tracking.

Why it’s important: Provides comprehensive insights across your entire application stack.

Installation:

# Gemfile
gem 'appsignal'

Then run:

bundle exec appsignal install YOUR_PUSH_API_KEY

Advantages:

• Error tracking alongside performance
• Host metrics integration
• Background job monitoring
• Magic Dashboard for quick insights

Website: https://appsignal.com
Documentation: https://docs.appsignal.com/ruby
GitHub: https://github.com/appsignal/appsignal-ruby

7. Derailed Benchmarks

What it does: Suite of benchmarks and performance tests for your application.

Why it’s important: Helps catch performance regressions before they hit production.

Installation:

# Gemfile
group :development, :test do
  gem 'derailed_benchmarks'
end

Usage examples:

# Memory usage at boot
bundle exec derailed bundle:mem

# Performance per route
bundle exec derailed exec perf:routes

Advantages:

• CI-friendly performance testing
• Memory usage analysis
• Route-based performance testing

GitHub: https://github.com/schneems/derailed_benchmarks
Documentation: https://github.com/schneems/derailed_benchmarks/blob/master/README.md

8. Flamegraph Generation

What it does: Visual representation of where time is being spent in your application.

Why it’s important: Provides an intuitive way to understand call stacks and hot paths.

Installation:

# Gemfile
gem 'flamegraph'
gem 'stackprof' # if not already installed

Usage example:

Flamegraph.generate('flamegraph.html') do
  # Code to profile
end

Advantages:

• Visual representation of performance
• Easy to spot hot paths
• Interactive exploration

GitHub: https://github.com/SamSaffron/flamegraph
Documentation: http://samsaffron.github.io/flamegraph/rails-startup.html

Additional Helpful Tools 🔧

9. Benchmark-ips

Benchmark-ips (iterations per second) is a superior benchmarking tool compared to Ruby’s standard Benchmark library. It provides:

1. Iterations-per-second measurement – More intuitive than raw time measurements
2. Statistical analysis – Shows standard deviation between runs
3. Comparison mode – Easily compare different implementations
4. Warmup phase – Accounts for JIT and cache warming effects

Benchmark-ips solves these problems and is particularly valuable for:

• Comparing algorithm implementations
• Testing performance optimizations
• Benchmarking gem alternatives
• Validating performance-critical code

GitHub: https://github.com/evanphx/benchmark-ips
Documentation: https://github.com/evanphx/benchmark-ips/blob/master/README.md

Installation

# Gemfile
gem 'benchmark-ips', group: :development

Basic Usage:

require 'benchmark/ips'

Benchmark.ips do |x|
  x.report("addition") { 1 + 2 }
  x.report("addition with to_s") { (1 + 2).to_s }
  x.compare!
end

Advanced Features:

Benchmark.ips do |x|
  x.time = 5 # Run each benchmark for 5 seconds
  x.warmup = 2 # Warmup time of 2 seconds
  
  x.report("Array#each") { [1,2,3].each { |i| i * i } }
  x.report("Array#map") { [1,2,3].map { |i| i * i } }
  
  # Add custom statistics
  x.config(stats: :bootstrap, confidence: 95)
  
  x.compare!
end

# Memory measurement
require 'benchmark/memory'

Benchmark.memory do |x|
  x.report("method1") { ... }
  x.report("method2") { ... }
  x.compare!
end

# Disable GC for more consistent results
Benchmark.ips do |x|
  x.config(time: 5, warmup: 2, suite: GCSuite.new)
end

Sample Output:

Warming up --------------------------------------
            addition    281.899k i/100ms
  addition with to_s    261.831k i/100ms
Calculating -------------------------------------
            addition      8.614M (± 1.2%) i/s -     43.214M in   5.015800s
  addition with to_s      7.017M (± 1.8%) i/s -     35.347M in   5.038446s

Comparison:
            addition:  8613594.0 i/s
  addition with to_s:  7016953.3 i/s - 1.23x slower

Key Advantages

1. Accurate comparisons with statistical significance
2. Warmup phase eliminates JIT/caching distortions
3. Memory measurements available through extensions
4. Customizable reporting with various statistics options

10. Rails Performance (Dashboard)

What is Rails Performance?

Rails Performance is a self-hosted alternative to New Relic/Skylight that provides:

1. Request performance tracking
2. Background job monitoring
3. Slowest endpoints identification
4. Error tracking
5. Custom event monitoring

Why It’s Important

For teams that:

• Can’t use commercial SaaS solutions
• Need to keep performance data in-house
• Want historical performance tracking
• Need simple setup without complex infrastructure

GitHub: https://github.com/igorkasyanchuk/rails_performance
Documentation: https://github.com/igorkasyanchuk/rails_performance/blob/master/README.md

Installation

# Gemfile
gem 'rails_performance', group: :development

Then run:

rails g rails_performance:install
rake db:migrate

Configuration

# config/initializers/rails_performance.rb
RailsPerformance.setup do |config|
  config.redis = Redis.new # optional, will use Rails.cache otherwise
  config.duration = 4.hours # store requests for 4 hours
  config.enabled = Rails.env.production?
  config.http_basic_authentication_enabled = true
  config.http_basic_authentication_user_name = 'admin'
  config.http_basic_authentication_password = 'password'
end

Accessing the Dashboard:

After installation, access the dashboard at:

http://localhost:3000/rails/performance

Custom Tracking:

# Track custom events
RailsPerformance.trace("custom_event", tags: { type: "import" }) do
  # Your code here
end

# Track background jobs
class MyJob < ApplicationJob
  around_perform do |job, block|
    RailsPerformance.trace(job.class.name, tags: job.arguments) do
      block.call
    end
  end
end

# Add custom fields to requests
RailsPerformance.attach_extra_payload do |payload|
  payload[:user_id] = current_user.id if current_user
end

# Track slow queries
ActiveSupport::Notifications.subscribe("sql.active_record") do |*args|
  event = ActiveSupport::Notifications::Event.new(*args)
  if event.duration > 100 # ms
    RailsPerformance.trace("slow_query", payload: {
      sql: event.payload[:sql],
      duration: event.duration
    })
  end
end

Sample Dashboard Views:

1. Requests Overview:
   • Average response time
   • Requests per minute
   • Slowest actions
2. Detailed Request View:
   • SQL queries breakdown
   • View rendering time
   • Memory allocation
3. Background Jobs:
   • Job execution time
   • Failures
   • Queue times

Key Advantages

1. Self-hosted solution – No data leaves your infrastructure
2. Simple setup – No complex dependencies
3. Historical data – Track performance over time
4. Custom events – Track any application events
5. Background jobs – Full visibility into async processes

Implementing a Complete Profiling Strategy

For a comprehensive approach, combine these tools at different stages:

1. Development:

• Rack MiniProfiler (always on)
• Bullet (catch N+1s early)
• RubyProf/StackProf (for deep dives)

1. CI Pipeline:

• Derailed Benchmarks
• Memory tests

1. Production:

• Skylight or AppSignal
• Error tracking with performance context

Sample Rails 8 Configuration

Here’s how to set up a complete profiling environment in a new Rails 8 app:

# Gemfile

# Development profiling
group :development do
  # Basic profiling
  gem 'rack-mini-profiler'
  gem 'bullet'
  
  # Deep profiling
  gem 'ruby-prof'
  gem 'stackprof'
  gem 'memory_profiler'
  gem 'flamegraph'
  
  # Benchmarking
  gem 'derailed_benchmarks', require: false
  gem 'benchmark-ips'
  
  # Dashboard
  gem 'rails_performance'
end

# Production monitoring (choose one)
group :production do
  gem 'skylight'
  # or
  gem 'appsignal'
  # or
  gem 'newrelic_rpm' # Alternative option
end

Then create an initializer for development profiling:

# config/initializers/profiling.rb
if Rails.env.development?
  require 'rack-mini-profiler'
  Rack::MiniProfilerRails.initialize!(Rails.application)

  Rails.application.config.after_initialize do
    Bullet.enable = true
    Bullet.alert = true
    Bullet.bullet_logger = true
    Bullet.rails_logger = true
  end
end

Conclusion

Profiling your Rails 8 application shouldn’t be an afterthought. By implementing these tools throughout your development lifecycle, you’ll catch performance issues early, maintain a fast application, and provide better user experiences.

Remember:

• Use development tools like MiniProfiler and Bullet daily
• Run deeper profiles with RubyProf before optimization work
• Monitor production with Skylight or AppSignal
• Establish performance benchmarks with Derailed

With this toolkit, you’ll be well-equipped to build and maintain high-performance Rails 8 applications.

Enjoy Rails! 🚀