Скачать или смотреть How to Start an Hikari Datasource When the DB is Not Available in Spring Boot

Learn how to configure your Spring Boot application to handle startup with Hikari Datasource even when your database is not available.
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This video is based on the question https://stackoverflow.com/q/77002103/ asked by the user 'Stefano Bossi' ( https://stackoverflow.com/u/9614332/ ) and on the answer https://stackoverflow.com/a/77002542/ provided by the user 'Ken Chan' ( https://stackoverflow.com/u/339637/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When developing applications with Spring Boot, integrating a datasource is essential for interacting with databases. However, issues may arise if your database is not available during startup. This can lead to frustrating errors that prevent your application from running. If you’re using HikariCP (a popular JDBC connection pool), understanding how to configure it to start even when the database is down can be a game-changer for your application's resilience.

In this guide, we'll walk through how to effectively set up your Hikari Datasource to start safely, even when the database is unavailable, and explore other important configurations and strategies to ensure your application can recover once the database is back online.

Understanding the Problem

When you set up a Hikari Datasource in a Spring Boot application, it usually requires a connection to a database to initiate the application context. If the database is down when your app starts, you typically end up with errors similar to:

[[See Video to Reveal this Text or Code Snippet]]

In your specific case, the JobsInit bean can't be created because it requires a connection to the database and fails to initialize correctly. This is a common situation that many developers encounter.

Solution Overview

Your Hikari configuration is made to handle connectivity issues after the application has started. It can even work in a focus mode where it tries to recover from disconnections seamlessly. However, to ensure that your application can start safely without connecting to the database, we need to implement a few tweaks.

Key Configuration Settings

HikariConfig Settings:

You've already set hikariConfig.setInitializationFailTimeout(-1);, which instructs Hikari not to fail immediately if it can't connect during initialization. This is a good start.

Handle Bean Initialization:

The core issue arises with other beans expecting a live connection, such as your JobsInit component. To address this:

Modify the way you handle your application's bean initialization.

Steps to Enable Fail-Safe Mode

1. Lazy Initialization

Consider using lazy initialization for beans that depend on the datasource connection. This way, they will only attempt to initialize when they are needed, rather than at application startup.

Add the following annotation on your Spring Boot application main class:

[[See Video to Reveal this Text or Code Snippet]]

2. Use Conditional Logic

For beans requiring a database connection, modify the logic within the JobsInit component to check for the availability of the database. Use conditional checks and handle failures gracefully.

Example:

[[See Video to Reveal this Text or Code Snippet]]

3. Health Checks and Recovery Mechanisms

To make it robust, consider implementing health checks or scheduling tasks that retry connecting to the database after startup. This can be done using a scheduled task that periodically checks if the database is back online.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

While it might seem challenging to start your Spring Boot application with Hikari Datasource when the database is down, it's definitely possible with the right configuration and approach. By using lazy initialization, adding conditional logic to bean creation, and setting up health checks, you can create a more resilient application that gracefully handles database unavailability.

Don't forget to test your configurations thoroughly to ensure that everything functions as expected during both normal operations and potential database downtime.

If you're facing similar challenges, implementing these strategies might just save you some valuable time and frustration!