How to Use ORM Connection Pooling Effectively

In software development, efficient database connection management is important for optimal performance and scalability. Object–Relational Mapping (ORM) has revolutionized database interactions, simplifying SQL queries. However, even with advanced ORM frameworks, poor connection management can impact performance.

In this article, We will learn about the ORM connection pooling technique, a key optimization for database access, How to Create a Pooled Connection, the Effects of Increasing Connections on a Database Server, and so on.

What is Connection Pooling?

• Connection pooling is a technique used to manage a pool of database connections that can be reused, rather than creating a new connection for every database request.
• By reusing connections, connection pooling reduces the overhead of creating and tearing down connections, which can improve application performance.
• Connection pooling is particularly useful in environments where the cost of establishing a new connection is high, such as when using SSL/TLS for encryption.
• The pool manager monitors the pool for idle connections and reuses them when possible, reducing the need to create new connections.
• If no idle connections are available, the pool manager can create a new connection, up to a configurable maximum limit, to meet the demand.

How Does Connection Pooling Works?

The inner workings of connection pooling are straightforward which following sequence of operations:

1. Client Request: This occurs each time an application requires a link through the database, the requests are sent to the connection pool manager for the response.
2. Pool Management: The connection pool manager checks for an idle connection in the pool to serve the client. If no idle connections are available, the manager can create a new connection, up to a set maximum limit.
3. Connection Reuse: Upon securing a suitable connection from the pool, the client application is duly entrusted with its custody, allowing it to execute the requisite database operations in a seamless fashion.
4. Connection Return: Upon completion of the database operations, the client dutifully returns the connection to the pool, where it stands ready to be reallocated for subsequent use by other clients.

Key Considerations for Acquiring a Database Connection

Now, let’s understand the connection pooling. But first, let’s understand the steps involved in establishing a database connection. Opening a connection is not just a simple task. It involves several operations, such as:

1. DNS Lookups: It may be that the client application somewhere along the route would be required to undergo DNS lookups to get the IP address of the intended database server to connect to.
2. TCP Connection Establishment: After DNS resolves to the IP address of the database server, TCP three-way handshake flows over the network to create the user connection to the database server.
3. Encryption Negotiation: The TLS handshake is performed only in cases in which secure communication is of primary importance. During this process, both parties negotiate and agree on encryption methods for the next session.
4. Session Parameter Exchange: Exchange of preferences and requirements occurs between the client and the database server during the initial step to define session parameters, like encoding parameters and time zone settings.
5. Authentication and Authorization: The database server verifies the client identity through authentication and authorization processes to make sure that the user who is trying to connect to the requested database objects in the database has the proper permissions and authority.
6. Query Execution: Once the connection has been made and the client application has been authenticated, the client running app can go ahead with its queries and fetch the outcomes that are required in order for it to perform its duties.
7. Session Termination: Upon completion of the DB operations the distinction is very impressive as it breaks down the database session, TLS encryption and TCP connection.

These stages in the process may looks simple and easy to perform, but they consume time and resources when establishing and maintaining the database connection.

Creating a Pooled Connection

Step 1: Choose Your ORM Tool

First, decide on the ORM tool on which we will be using (For example: SQLAlchemy for Python, Hibernate for Java). Different ORMs have different ways of implementing connection pooling.

Step 2: Install Required Libraries

Make sure we have installed all necessary libraries or modules for our ORM. Some ORMs come with built-in support for connection pooling, while others might require additional packages.

Step 3: Configure Your ORM Settings

Look into our ORM’s documentation to find how to configure connection pooling. we typically need to specify parameters like pool size, max overflow, and pool timeout.

• Pool Size: The number of connections to keep in the pool.
• Max Overflow: The maximum number of connections that can be created beyond the pool size.
• Pool Timeout: The number of seconds to wait before timing out when trying to retrieve a connection from the pool.

Step 4: Initialize Your Connection Pool

Once we have configured the settings, initialize our connection pool according to our ORM’s instructions. This usually involves creating an engine or a session factory.

Step 5: Use the ORM as Usual

With the pooled connection setup, we can now proceed to use our ORM for database operations. The ORM will manage the connection pool under the hood, giving we improved performance and resource utilization.

Integrating a Connection Pooler: Different Approaches

1. Built-in Support: Many ORMs come with built-in support for connection pooling. Using the built-in mechanism is the simplest way to get started.
2. External Pooling Libraries: For ORMs that do not support pooling or if we require more advanced features, we can use external libraries like HikariCP (for Java) or PGBouncer (for PostgreSQL databases).
3. Database-Side Pooling: Some databases offer their connection pooling capabilities. While this is not directly related to ORM, it can be a complementary strategy.

What are the Effects of Increasing Connections on Database Server?

In terms of resources, the impact that the connections count on the database server could not be ignored. As more and more database servers become a source of connection, to the same extend they will be required to address the constrained quantity of the resources. Some of the key resource implications include:

1. Memory Usage: Each active connection consumes a notable amount of memory on the database server to manage session states and handle client requests. Studies suggest PostgreSQL may require between 3MB to 14.5MB per connection based on the workload
2. CPU Utilization: As more connections are added, the server’s CPU usage increases, potentially slowing down transaction execution.
3. Resource Contention: Ensure database design accommodates shared resources, like server capacity for caching, to avoid application degradation, impacting performance, responsiveness, and client perception.

How does the Number of Connections Affect Client Applications?

The implications of the same connection count carry further than the machine where database server resides and create a stealth effect on the client app as well. Consider the following implications:

1. Connection Limits: Database servers quickly reach their maximum connection limit. When this limit is exceeded, new connection requests are rejected, leading to potential failures in client applications
2. Client Handling: Clients should be equipped with effective modules for recovering from connection errors and retries. Using algorithms like exponential backoff can help manage the density of failed attempts, but they can become complex and add overhead.
3. Performance Degradation: Connection failures lead to noticeable delays for end-users, causing them to wait for query execution and replies, leading to a poor user experience. With each denied connection request, the risk of service disruption and dissatisfaction grows, emphasizing the need for effective connection management systems.

What are Some Common External Connection Poolers?

A plethora of external connection pooling solutions abound, catering to diverse programming ecosystems and database platforms. Among the most prominent exemplars are:

1. HikariCP: A superlative JDBC connection pool acclaimed for its lightning-fast performance and minimal footprint, particularly in Java-centric environments.
2. PgBouncer: A lightweight connection pooler tailored expressly for PostgreSQL databases, distinguished by its ability to seamlessly scale to accommodate burgeoning connection demands while preserving resource efficiency.
3. ConnectionPool: A versatile and extensible pooling library catering to Python aficionados, replete with an array of customization options and compatibility with an eclectic assortment of database drivers.
4. Microsoft Enterprise Library Data Access Application Block (DAAB): A venerable .NET stalwart renowned for its robust connection pooling capabilities, empowering .NET developers to utilize the power of connection pooling with complete ease and effectiveness.

Difference Between Internal and External Pooling

Connection pooling manifests in two distinct incarnations, each characterized by its modality of deployment and management:

Feature	Internal Pooling	External Pooling
Integration	Integrated within the ORM. No additional setup required.	Requires separate setup and possibly additional libraries.
Control & Flexibility	Limited to what the ORM offers.	More control and flexibility. Can be customized.
Performance	Good for most applications.	Potentially better, optimized for specific DBMS.
Complexity	Simple to configure. Ideal for beginners.	Might add complexity. Requires understanding of both the ORM and the pooling solution.
Use Case	Small to medium-sized applications.	High-load applications or when specific pooling features are needed.

Conclusion

In the world of software engineering, making sure that applications run fast and can handle a lot of users at the same time is super important. That’s where something called ORM connection pooling comes in. It’s basically a way to manage how your application talks to the database efficiently.

Think of connection pooling like a carpool system for database connections. Instead of each request to your database needing to start up a new connection (which takes time and resources), connection pooling keeps a few connections ready to go. When a new request comes in, it can just hop into one of these ready connections, making everything quicker and smoother.