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

This error means Sidekiq cannot connect to Redis, which it uses as its job queue backend. Redis may not be running, the connection URL is incorrect, or the connection pool is exhausted. Start Redis, verify the REDIS_URL environment variable, and ensure your Sidekiq configuration has the correct Redis connection settings.

Reading the Stack Trace

Here's what each line means:

• sidekiq (7.2.1) lib/sidekiq/redis_connection.rb:45:in `create': Sidekiq attempts to create a Redis connection from its connection pool and fails.
• sidekiq (7.2.1) lib/sidekiq/client.rb:68:in `raw_push': The Sidekiq client tries to push a job to Redis but the connection fails.
• app/controllers/orders_controller.rb:15:in `create': The controller action enqueues a Sidekiq job which triggers the Redis connection attempt.

Common Causes

# $ redis-cli ping
# Could not connect to Redis at 127.0.0.1:6379: Connection refused
# Sidekiq cannot start without Redis

# config/initializers/sidekiq.rb
Sidekiq.configure_server do |config|
  config.redis = { url: 'redis://wrong-host:6379/0' }
end

# config/sidekiq.yml
:concurrency: 25

# But Redis pool is only:
Sidekiq.configure_server do |config|
  config.redis = { url: ENV['REDIS_URL'], size: 5 }  # Too small for 25 threads
end

The Fix

Use the REDIS_URL environment variable for configuration flexibility across environments. Add timeout settings for resilience. Ensure both server and client configurations point to the same Redis instance.

Sidekiq.configure_server do |config|
  config.redis = { url: 'redis://wrong-host:6379/0' }
end

Sidekiq.configure_client do |config|
  config.redis = { url: 'redis://wrong-host:6379/0' }
end

Sidekiq.configure_server do |config|
  config.redis = {
    url: ENV.fetch('REDIS_URL', 'redis://localhost:6379/0'),
    pool_timeout: 5,
    network_timeout: 5
  }
end

Sidekiq.configure_client do |config|
  config.redis = {
    url: ENV.fetch('REDIS_URL', 'redis://localhost:6379/0'),
    pool_timeout: 5,
    network_timeout: 5
  }
end

Testing the Fix

require 'rails_helper'
require 'sidekiq/testing'

RSpec.describe 'Sidekiq Redis connection' do
  it 'enqueues jobs successfully' do
    Sidekiq::Testing.fake!
    expect {
      OrderProcessingJob.perform_async(1)
    }.to change(OrderProcessingJob.jobs, :size).by(1)
  end

  it 'processes jobs without errors' do
    Sidekiq::Testing.inline!
    order = create(:order, status: 'pending')
    OrderProcessingJob.perform_async(order.id)
    expect(order.reload.status).to eq('processing')
  end
end

Run your tests:

bundle exec rspec spec/jobs/order_processing_job_spec.rb

Pushing Through CI/CD

git checkout -b fix/sidekiq-redis-connection,git add config/initializers/sidekiq.rb,git commit -m "fix: configure Sidekiq Redis with env var and timeouts",git push origin fix/sidekiq-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. Verify Sidekiq starts and connects to Redis.
4. Open a pull request.
5. Merge and verify job processing in staging.

Frequently Asked Questions