DB Connection Pools: The Chefs Behind Your App’s Kitchen

#database #db

When developing code that involves connecting to databases, you may come across a term called DB pools.

Let’s understand it.

What is a DB Pool?

It is basically a reusable collection of open connections to a database.

Instead of creating a new connection every time you run a query, the pool keeps several connections open so they can be reused instantly.

The reason connection pools exist

Opening a new DB connection is slow and expensive because it involves a number of things like:

Authenticating
Allocating memory
Starting a session
Sending startup packets

Key concepts of a connection pool

Maximum connections: The maximum number of connections that will ever be open.
Idle connections: Connections that are unused but open; they are ready to serve new work instantly.
Borrow and Return
- When an application needs a connection, it borrows one from the pool.
- After that, it will run the queries and return it to the pool.
Connection Lifetime: Pools set rules to close connections after a specified period of time, recreate them if the DB restarts, etc.
Concurrency: Multiple threads or requests can use different connections simultaneously, as long as the pool has capacity.
Backpressure
- There can be cases where all connections are busy.
- In such cases, new requests wait until a connection is free or time out if they wait too long.
- This prevents flooding the database with too many connections.

What happens when connection pools are not used

Without a pool, every request creates a new connection.

And your DB will end up facing a situation like

1000 connections opened
Postgres starts rejecting new ones with “too many clients”
Your server may slow down or crash because it cannot get a connection
The whole system becomes unstable

With the pool, we have rules set in place to prevent such collapses. For eg:

Max 20 connections
All reused
Helps the System stays more stable

Wrapping up

Hope you got an idea of why pools are so essential when developing software, and how various situations are handled with pools.

If you’ve ever struggled with repetitive tasks, obscure commands, or debugging headaches, this platform is here to make your life easier. It’s free, open-source, and built with developers in mind.