Fix: ActiveRecord::ConnectionTimeoutError (MAYBE-RAILS-CY)

[revise-dev]

The ActiveRecord::ConnectionTimeoutError occurs when the application runs out of available database connections. This is happening because the current connection pool size (11) is insufficient for the application's concurrent processing needs.

Looking at the application architecture:

1. Puma web server is configured to use 3 threads per worker (from RAILS_MAX_THREADS)
2. GoodJob background processor has 5 queue threads:
   • 1 thread for latency_low
   • 2 threads for latency_low,latency_medium
   • 1 thread for latency_low,latency_medium,latency_high
   • 1 thread for catch-all queue
3. Additional GoodJob threads:
   • 1 thread for job listener
   • 1 thread for cron
   • 1 thread for executor

Total minimum threads needed:

• Puma: 3 threads × 1 worker = 3 connections
• GoodJob queues: 5 connections
• GoodJob system: 3 connections
• Buffer for peak loads: 9 connections
  Total: 20 connections needed

The current pool size of 11 doesn't account for peak loads and potential concurrent access patterns. By increasing the pool to 20, we ensure there are enough connections available for all concurrent operations while maintaining a buffer for unexpected spikes in database access.

Tests should be added:

# spec/config/database_config_spec.rb
require 'rails_helper'

RSpec.describe "Database Configuration" do
  it "has sufficient connection pool size for concurrent operations" do
    config = ActiveRecord::Base.configurations.configurations.find do |c| 
      c.env_name == Rails.env
    end
    
    min_required_pool = 20
    expect(config.pool).to be >= min_required_pool
  end

  it "handles concurrent database operations without timeout" do
    threads = []
    20.times do
      threads << Thread.new do
        Account.transaction do
          Account.first
          sleep 0.1 # Simulate work
        end
      end
    end
    expect { threads.each(&:join) }.not_to raise_error
  end
end

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