Set Up Connection Pooling

Configure database connection pooling for better performance and resource management.

Prerequisites

• CQL installed and configured

• Database connection working

Basic Pool Configuration

Configure pool settings when defining your schema:

MyDB = CQL::Schema.define(
  :my_db,
  adapter: CQL::Adapter::Postgres,
  uri: ENV["DATABASE_URL"]
) do
  # Pool settings
  pool_size 25
  checkout_timeout 5.seconds
  retry_attempts 3
end

Pool Settings

pool_size

Maximum number of connections in the pool:

pool_size 25  # Default: 5

Guidelines:

• Web apps: 2-3x your web server threads

• Background jobs: Match worker count

• Maximum: Check database limits

checkout_timeout

How long to wait for an available connection:

checkout_timeout 5.seconds  # Default: 5 seconds

If timeout is reached, raises CQL::ConnectionTimeout.

retry_attempts

Number of times to retry failed connections:

retry_attempts 3  # Default: 1

Environment-Specific Configuration

pool = case ENV["APP_ENV"]?
       when "production"  then 25
       when "staging"     then 10
       else                    5
       end

MyDB = CQL::Schema.define(:my_db, adapter: CQL::Adapter::Postgres, uri: db_url) do
  pool_size pool
end

Monitoring Pool Health

# Check current pool status
stats = MyDB.pool_stats
puts "Available: #{stats[:available]}"
puts "In use: #{stats[:busy]}"
puts "Size: #{stats[:size]}"

Verify Configuration

Test your pool under load:

# Simulate concurrent connections
10.times do
  spawn do
    User.count
    puts "Connection successful"
  end
end
sleep 1.second

Common Issues

Pool exhaustion:

• Increase pool_size

• Reduce connection hold time

• Use transactions efficiently

Connection timeouts:

• Increase checkout_timeout

• Check network latency

• Verify database is responsive

See Also

• Configure Database Connection

• Configure Multiple Environments

• Enable SSL Connections