Graceful Shutdown of Spring Boot ThreadPoolTaskScheduler to Prevent Redis Errors

Problem Description

When using @Async with a custom ThreadPoolTaskScheduler, shutting down the application may cause asynchronous tasks that still access Redis to fail because the Redis connection pool is destroyed before the tasks finish, resulting in a JedisConnectionException.

Reproducing the Issue

Define a ThreadPoolTaskScheduler bean, create async methods that depend on StringRedisTemplate, and write a test that submits many tasks in a loop and calls System.exit(0) after the last iteration to simulate abrupt shutdown. The stack trace shows errors from the Redis connection pool.

Root Cause Analysis

The thread pool is closed without waiting for running tasks, so Redis resources are released while tasks are still executing.

Solution

Configure the ThreadPoolTaskScheduler to wait for tasks on shutdown:

@Bean("taskExecutor")
public Executor taskExecutor() {
    ThreadPoolTaskScheduler executor = new ThreadPoolTaskScheduler();
    executor.setPoolSize(20);
    executor.setThreadNamePrefix("taskExecutor-");
    executor.setWaitForTasksToCompleteOnShutdown(true);
    executor.setAwaitTerminationSeconds(60);
    return executor;
}

The key method setWaitForTasksToCompleteOnShutdown(true) ensures that the scheduler finishes all submitted tasks before the Spring context destroys other beans such as the Redis connection pool. The setAwaitTerminationSeconds(60) limits the waiting time to avoid indefinite blocking.

Complete Example

The full source code, including the task class, configuration, and test, is available in the SpringBoot‑Learning repository (GitHub/Gitee).