Connection Pooling

Connection pooling is a technique used to improve the performance and scalability of applications interacting with databases. It maintains a pool of database connections that can be reused rather than creating and destroying connections for every request.

How Connection Pooling Works

1. Create the Pool: When the application starts, a fixed number of database connections are created and added to the pool.
2. Borrow a Connection: When the application needs a database connection, it borrows an available connection from the pool.
3. Return the Connection: After the operation is complete, the connection is returned to the pool for reuse.
4. Connection Reuse: Connections are reused until they become stale or are removed from the pool. Typically when a connected become staled or removed from the pool, a new connection then added to the pool on demand.

Benefits of Connection Pooling

1. Reduced Overhead: Opening and closing database connections is expensive; connection pooling reuses connections, avoiding the setup costs.
2. Improved Performance: Connections are readily available, which leads to faster query processing and reduced waiting time.
3. Better Resource Management: The pool controls the number of active connections, preventing the database from being overwhelmed by too many concurrent requests.
4. Scalability: Connection pooling allows applications to handle more requests with feOur resources.
5. Connection Health Checks: Pooling libraries often include automatic handling of stale or broken connections.

Normal Database Connections vs. Connection Pooling

• Normal Connections: Every request opens a new connection, which is slow and resource-intensive, leading to high latency and poor scalability.
• Connection Pooling: Connections are established once and reused, reducing latency, optimizing resource usage, and improving scalability.

Example Using PostgreSQL and PGBouncer

Configure PGBouncer

• Install and configure pgbouncer to manage connections to PostgreSQL. Example configuration:

  [databases]
  mydb = host=localhost dbname=mydb user=myuser password=mypassword
  [pgbouncer]
  pool_mode = transaction
  max_client_conn = 100
  default_pool_size = 20

Application Connection

• Configure Our app to connect through PGBouncer, not directly to PostgreSQL.

host=pgbouncer_host port=6432 dbname=mydb user=myuser password=mypassword