Fix Redis::CannotConnectError: Error connecting to Redis on 127.0.0.1:6379 (Errno::ECONNREFUSED) in Rails

This error means your Rails application cannot connect to the Redis server. Redis may not be running, the connection URL may be wrong, or the server is overloaded. Start Redis with redis-server, verify the connection URL in your configuration, and check that the Redis port is accessible from your application server.

Reading the Stack Trace

Here's what each line means:

• redis (5.1.0) lib/redis/client.rb:68:in `connect': The Redis gem is unable to establish a TCP connection to the Redis server.
• redis (5.1.0) lib/redis/client.rb:34:in `establish_connection': The connection attempt fails with ECONNREFUSED, meaning the server is not listening on the expected port.
• actionpack (7.1.3) lib/action_dispatch/middleware/session/cache_store.rb:55:in `get_session': Rails is trying to use Redis as a session store but cannot connect.

Common Causes

# Redis is not running
# $ redis-cli ping
# Could not connect to Redis at 127.0.0.1:6379: Connection refused

# config/initializers/redis.rb
$redis = Redis.new(host: 'localhost', port: 6380)  # Wrong port, Redis is on 6379

# config/initializers/redis.rb
$redis = ConnectionPool.new(size: 2) { Redis.new }  # Pool too small for concurrent requests

The Fix

Use the REDIS_URL environment variable for configuration and add timeout and reconnection settings. This makes the connection configurable per environment and more resilient to transient failures.

# config/initializers/redis.rb
$redis = Redis.new(host: 'localhost', port: 6380)

# config/initializers/redis.rb
$redis = Redis.new(
  url: ENV.fetch('REDIS_URL', 'redis://localhost:6379/0'),
  connect_timeout: 5,
  read_timeout: 1,
  write_timeout: 1,
  reconnect_attempts: 3
)

Testing the Fix

require 'rails_helper'

RSpec.describe 'Redis connection' do
  it 'connects to Redis successfully' do
    expect { Redis.new(url: ENV.fetch('REDIS_URL', 'redis://localhost:6379/0')).ping }.not_to raise_error
  end

  it 'returns PONG on ping' do
    redis = Redis.new(url: ENV.fetch('REDIS_URL', 'redis://localhost:6379/0'))
    expect(redis.ping).to eq('PONG')
  end

  it 'handles connection failure gracefully' do
    bad_redis = Redis.new(url: 'redis://localhost:9999/0', connect_timeout: 1)
    expect { bad_redis.ping }.to raise_error(Redis::CannotConnectError)
  end
end

Run your tests:

bundle exec rspec spec/integration/redis_spec.rb

Pushing Through CI/CD

git checkout -b fix/rails-redis-connection,git add config/initializers/redis.rb,git commit -m "fix: use REDIS_URL env var with timeout and reconnect settings",git push origin fix/rails-redis-connection

Your CI config should look something like this:

name: CI
on:
  pull_request:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    services:
      postgres:
        image: postgres:16
        env:
          POSTGRES_PASSWORD: postgres
        ports: ['5432:5432']
      redis:
        image: redis:7
        ports: ['6379:6379']
    steps:
      - uses: actions/checkout@v4
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: '3.3'
          bundler-cache: true
      - run: bin/rails db:setup
      - run: bundle exec rspec

The Full Manual Process: 18 Steps

Here's every step you just went through to fix this one bug:

1. Notice the error alert or see it in your monitoring tool
2. Open the error dashboard and read the stack trace
3. Identify the file and line number from the stack trace
4. Open your IDE and navigate to the file
5. Read the surrounding code to understand context
6. Reproduce the error locally
7. Identify the root cause
8. Write the fix
9. Run the test suite locally
10. Fix any failing tests
11. Write new tests covering the edge case
12. Run the full test suite again
13. Create a new git branch
14. Commit and push your changes
15. Open a pull request
16. Wait for code review
17. Merge and deploy to production
18. Monitor production to confirm the error is resolved

Total time: 30-60 minutes. For one bug.

gem install bugstack

require 'bugstack'

Bugstack.init(api_key: ENV['BUGSTACK_API_KEY'])

Deploying the Fix (Manual Path)

1. Ensure Redis is running and accessible.
2. Set the REDIS_URL environment variable.
3. Run integration specs to verify the connection.
4. Open a pull request.
5. Merge and verify Redis connectivity in staging.

Frequently Asked Questions