In this article, we will analyze the causes of memory leaks and high CPU usage in Spring Boot applications, explore debugging techniques, and provide best practices to optimize application performance and scalability.

Understanding Memory Leaks and High CPU Usage in Spring Boot

Spring Boot applications can experience memory leaks and high CPU usage due to unoptimized resource handling, inefficient caching, and excessive thread creation. Common causes include:

• Improperly scoped Spring beans leading to memory retention.
• Unreleased database connections causing connection pool exhaustion.
• High thread contention due to unoptimized thread pools.
• Unbounded caches consuming excessive heap space.
• Excessive logging and unnecessary background tasks.

Common Symptoms

• OutOfMemoryErrors (OOM) despite sufficient allocated heap size.
• High CPU utilization even during low traffic periods.
• Application crashes due to thread pool exhaustion.
• Slow API response times under load.
• Gradual degradation of application performance over time.

Diagnosing Memory Leaks and High CPU Usage in Spring Boot

1. Checking JVM Memory Utilization

Monitor heap memory usage in real-time:

jmap -histo:live $(pgrep -f java)

2. Identifying Long-Lived Spring Beans

Detect improperly scoped beans causing memory retention:

@Scope("prototype") // Avoid using singleton scope where unnecessary

3. Detecting Connection Pool Exhaustion

Monitor database connections in HikariCP:

SELECT * FROM pg_stat_activity;

4. Profiling High CPU Usage

Identify CPU-intensive threads:

top -H -p $(pgrep -f java)

5. Analyzing Thread Dump

Generate and analyze a thread dump:

jstack $(pgrep -f java) > thread_dump.txt

Fixing Memory Leaks and High CPU Usage in Spring Boot

Solution 1: Managing Spring Bean Scope

Ensure beans are correctly scoped to avoid memory retention:

@Scope("prototype")
@Bean
public MyService myService() {
    return new MyService();
}

Solution 2: Optimizing Connection Pool Settings

Configure HikariCP to prevent connection exhaustion:

spring.datasource.hikari.maximum-pool-size=10

Solution 3: Using Efficient Thread Pool Management

Limit thread creation and optimize thread pools:

@Bean
public Executor taskExecutor() {
    return Executors.newFixedThreadPool(10);
}

Solution 4: Implementing Caching Best Practices

Configure cache eviction policies to prevent unbounded growth:

@Bean
public CacheManager cacheManager() {
    return new ConcurrentMapCacheManager("users");
}

Solution 5: Reducing Excessive Logging

Disable debug logging in production:

logging.level.root=INFO

Best Practices for High-Performance Spring Boot Applications

• Use proper bean scoping to avoid unintended memory retention.
• Optimize database connection pooling to prevent resource exhaustion.
• Manage thread pools efficiently to avoid CPU spikes.
• Implement caching strategies to reduce redundant computations.
• Monitor application metrics to detect performance issues early.

Conclusion

Memory leaks and high CPU usage in Spring Boot can severely impact application stability and scalability. By optimizing bean scope, managing thread pools, and configuring efficient caching, developers can ensure smooth and performant Spring Boot applications.

FAQ

1. Why is my Spring Boot application running out of memory?

Common causes include unbounded caches, singleton beans retaining large objects, and inefficient resource management.

2. How do I fix high CPU usage in Spring Boot?

Optimize thread pools, reduce background tasks, and analyze CPU-intensive operations using thread dumps.

3. What is the best way to manage database connections?

Use connection pooling with HikariCP and set appropriate limits on the connection pool size.

4. How do I detect memory leaks in a Spring Boot application?

Use jmap to analyze heap memory and identify long-lived objects.

5. How can I improve the performance of my Spring Boot application?

Implement caching, optimize database queries, manage logging levels, and use efficient bean scoping strategies.