Automate MinIO Image Cleanup with Spring Boot Scheduled Tasks and Cron

Introduction

In project development we use MinIO as an image storage service. Over time many historical images become unnecessary, so a scheduled cleanup is needed to delete files older than a specified date.

Dependencies

Core dependencies: MinIO client and Spring Boot starter (which already includes scheduling support).

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Delete Methods

Utility class MinioUtil provides methods: deleteDateFoldersBefore(LocalDate endExclusive): deletes all date‑based directories before the given date. deleteSingleFolder(String prefix): deletes all objects under a single prefix.

File naming follows the pattern /bucketName/yyyy-MM-dd/uuid.extension.

Implementation Details

Methods use MinIO's listObjects with lazy pagination and removeObjects to batch delete. Idempotency is ensured by ignoring already deleted objects.

Cron Expression Configuration

Spring's @Scheduled(cron = "...") supports 6‑field cron expressions. Examples include:

Every minute: 0 * * * * ? Every day at 1 AM: 0 0 1 * * ? First day of each month at 3 AM:

0 0 3 1 * ?

Thread‑Pool Scheduler

Multiple scheduled tasks share a single thread by default. Configuring a ThreadPoolTaskScheduler improves isolation and parallelism.

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Asynchronous Execution

Long‑running tasks should run asynchronously to avoid blocking the scheduler. Define a ThreadPoolTaskExecutor and annotate the task method with @Async.

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Extending the Solution

Properties can be externalized to control enable flag, retain days, earliest date, and cron expression. The utility class reads these values at startup, and the scheduled task uses them to compute the cutoff date.

Testing

A JUnit test invokes minioUtil.deleteDateFoldersBefore with a custom date to verify the cleanup logic.

Additional Resources

Online cron validators such as crontab.guru are recommended for testing expressions.