Understanding Hikari Connection Pool

Oct 13, 2025 by talynt.org 57 views

Introduction

As a developer, encountering unexpected errors in a production environment can be frustrating and time-consuming to resolve. In this article, we will discuss a common issue with Hikari connection pool in a Spring Boot application, specifically the "Invalid Operation, NOT Connected" error. This error can occur when the application is running fine for a long time but suddenly stops due to a connection pool issue.

Understanding Hikari Connection Pool

Hikari connection pool is a high-performance connection pool that is widely used in Java applications, including Spring Boot. It is designed to provide a fast and efficient way to manage database connections. However, like any other connection pool, it can encounter issues that can cause the application to fail.

Causes of Hikari Connection IO Error

There are several reasons why the Hikari connection IO error can occur. Some of the common causes include:

Connection leak: A connection leak occurs when a connection is not closed properly, causing the connection pool to run out of available connections.
Invalid database configuration: An invalid database configuration can cause the connection pool to fail, resulting in the "Invalid Operation, NOT Connected" error.
Timeout issues: Timeout issues can occur when the connection pool is unable to acquire a connection within the specified time limit.
Resource leaks: Resource leaks can occur when a resource, such as a connection or a statement, is not closed properly, causing the connection pool to fail.

Symptoms of Hikari Connection IO Error

The Hikari connection IO error can manifest in different ways, including:

Application crashes: The application can crash suddenly, resulting in a "Invalid Operation, NOT Connected" error.
Connection pool exhaustion: The connection pool can become exhausted, causing the application to fail.
Slow performance: The application can experience slow performance due to the connection pool issues.

Resolving Hikari Connection IO Error

To resolve the Hikari connection IO error, you can try the following steps:

Check the database configuration: Verify that the database configuration is correct and that the connection pool is properly configured.
Monitor the connection pool: Monitor the connection pool to identify any issues, such as connection leaks or timeout issues.
Close connections properly: Ensure that connections are closed properly to prevent connection leaks.
Increase the connection pool size: Increase the connection pool size to ensure that there are enough connections available.
Use a connection pool debugger: Use a connection pool debugger to identify any issues with the connection pool.

Example of Hikari Connection Pool Configuration

Here is an example of a Hikari connection pool configuration in a Spring Boot application:

@Configuration
public class DatabaseConfig {
@Bean
public DataSource dataSource() {
    HikariDataSource dataSource = new HikariDataSource();
    dataSource.setJdbcUrl(&quot;jdbc:oracle:thin:@localhost:1521:ORCL&quot;);
    dataSource.setUsername(&quot;username&quot;);
    dataSource.setPassword(&quot;password&quot;);
    dataSource.setDriverClassName(&quot;oracle.jdbc.driver.OracleDriver&quot;);
    dataSource.setConnectionTimeout(30000);
    dataSource.setIdleTimeout(30000);
    dataSource.setMaxLifetime(30000);
    dataSource.setMinimumIdle(5);
    dataSource.setMaximumPoolSize(20);
    return dataSource;
}

}

Conclusion

In conclusion, the Hikari connection IO error can occur due to various reasons, including connection leaks, invalid database configuration, timeout issues, and resource leaks. To resolve this error, you can try checking the database configuration, monitoring the connection pool, closing connections properly, increasing the connection pool size, and using a connection pool debugger. By following these steps, you can resolve the Hikari connection IO error and ensure that your application runs smoothly.

Troubleshooting Tips

Here are some additional troubleshooting tips to help you resolve the Hikari connection IO error:

Enable connection pool logging: Enable connection pool logging to identify any issues with the connection pool.
Use a connection pool monitor: Use a connection pool monitor to monitor the connection pool and identify any issues.
Check the database logs: Check the database logs to identify any issues with the database.
Use a database debugger: Use a database debugger to identify any issues with the database.

Best Practices

Here are some best practices to help you prevent the Hikari connection IO error:

Use a connection pool: Use a connection pool to manage database connections.
Configure the connection pool properly: Configure the connection pool properly to ensure that there are enough connections available.
Monitor the connection pool: Monitor the connection pool to identify any issues.
Close connections properly: Close connections properly to prevent connection leaks.
Increase the connection pool size: Increase the connection pool size to ensure that there are enough connections available.

Common Issues

Here are some common issues that can cause the Hikari connection IO error:

Connection leak: A connection leak occurs when a connection is not closed properly, causing the connection pool to run out of available connections.
Invalid database configuration: An invalid database configuration can cause the connection pool to fail, resulting in the "Invalid Operation, NOT Connected" error.
Timeout issues: Timeout issues can occur when the connection pool is unable to acquire a connection within the specified time limit.
Resource leaks: Resource leaks can occur when a resource, such as a connection or a statement, is not closed properly, causing the connection pool to fail.

Conclusion

Q: What is the Hikari connection IO error?

A: The Hikari connection IO error is a common issue that occurs when the Hikari connection pool is unable to acquire a connection from the database. This error can manifest in different ways, including the "Invalid Operation, NOT Connected" error.

Q: What are the common causes of the Hikari connection IO error?

A: The common causes of the Hikari connection IO error include:

Connection leak: A connection leak occurs when a connection is not closed properly, causing the connection pool to run out of available connections.
Invalid database configuration: An invalid database configuration can cause the connection pool to fail, resulting in the "Invalid Operation, NOT Connected" error.
Timeout issues: Timeout issues can occur when the connection pool is unable to acquire a connection within the specified time limit.
Resource leaks: Resource leaks can occur when a resource, such as a connection or a statement, is not closed properly, causing the connection pool to fail.

Q: How can I resolve the Hikari connection IO error?

A: To resolve the Hikari connection IO error, you can try the following steps:

Check the database configuration: Verify that the database configuration is correct and that the connection pool is properly configured.
Monitor the connection pool: Monitor the connection pool to identify any issues, such as connection leaks or timeout issues.
Close connections properly: Ensure that connections are closed properly to prevent connection leaks.
Increase the connection pool size: Increase the connection pool size to ensure that there are enough connections available.
Use a connection pool debugger: Use a connection pool debugger to identify any issues with the connection pool.

Q: What are some best practices to prevent the Hikari connection IO error?

A: Here are some best practices to help you prevent the Hikari connection IO error:

Use a connection pool: Use a connection pool to manage database connections.
Configure the connection pool properly: Configure the connection pool properly to ensure that there are enough connections available.
Monitor the connection pool: Monitor the connection pool to identify any issues.
Close connections properly: Close connections properly to prevent connection leaks.
Increase the connection pool size: Increase the connection pool size to ensure that there are enough connections available.

Q: What are some common issues that can cause the Hikari connection IO error?

A: Here are some common issues that can cause the Hikari connection IO error:

Connection leak: A connection leak occurs when a connection is not closed properly, causing the connection pool to run out of available connections.
Invalid database configuration: An invalid database configuration can cause the connection pool to fail, resulting in the "Invalid Operation, NOT Connected" error.
Timeout issues: Timeout issues can occur when the connection pool is unable to acquire a connection within the specified time limit.
Resource leaks: Resource leaks can occur when a resource, such as a connection or a statement, is not closed properly, causing the connection pool to fail.

Q: How can I troubleshoot the Hikari connection IO error?

A: To troubleshoot the Hikari connection IO error, you can try the following steps:

Enable connection pool logging: Enable connection pool logging to identify any issues with the connection pool.
Use a connection pool monitor: Use a connection pool monitor to monitor the connection pool and identify any issues.
Check the database logs: Check the database logs to identify any issues with the database.
Use a database debugger: Use a database debugger to identify any issues with the database.

Q: What are some tools that can help me troubleshoot the Hikari connection IO error?

A: Here are some tools that can help you troubleshoot the Hikari connection IO error:

Connection pool debugger: A connection pool debugger can help you identify any issues with the connection pool.
Connection pool monitor: A connection pool monitor can help you monitor the connection pool and identify any issues.
Database debugger: A database debugger can help you identify any issues with the database.
Database logs: Database logs can help you identify any issues with the database.

Q: How can I prevent the Hikari connection IO error in the future?

A: To prevent the Hikari connection IO error in the future, you can try the following steps:

Use a connection pool: Use a connection pool to manage database connections.
Configure the connection pool properly: Configure the connection pool properly to ensure that there are enough connections available.
Monitor the connection pool: Monitor the connection pool to identify any issues.
Close connections properly: Close connections properly to prevent connection leaks.
Increase the connection pool size: Increase the connection pool size to ensure that there are enough connections available.