How to Resolve ServiceNow JVM Tenured Space Overflow Issues

Is your ServiceNow MID Server facing unexpected slowdowns and crashes? 🤔 It might be grappling with JVM tenured space overflow, a critical issue in Java virtual machine environments. But don’t worry! In this article, we’ll walk you through diagnosing and resolving this problem. Get ready to discover expert tips for troubleshooting JVM tenured space overflow in your ServiceNow MID server setup, ensuring the resilience and optimal performance of your applications. Ready to confront this challenge head-on? Let’s explore the solution together! 

Impact of JVM Tenured Space Overflow

When the JVM’s tenured space overflows, it can have several negative consequences for Java applications:

1. OutOfMemoryError (OOM): Tenured space overflow often results in the JVM throwing an OutOfMemoryError. This error indicates that the tenured generation, where long-lived objects are stored, has reached its maximum capacity and cannot accommodate additional objects. As a result, the application may crash or become unresponsive.

2. Increased Garbage Collection (GC) Overhead: When tenured space is close to overflowing, the garbage collector (GC) may need to work harder to reclaim memory by identifying and collecting unreachable objects. This can lead to increased GC activity, longer pauses, and degraded application performance.

3. Performance Degradation: As the JVM struggles to manage memory within the tenured space, application performance may suffer. Increased GC overhead, longer pauses, and potential application slowdowns can negatively impact user experience and responsiveness.

4. System Instability: Tenured space overflow can destabilize the JVM and the underlying system. OutOfMemoryErrors may occur unpredictably, causing application crashes or system failures. This instability can disrupt critical business operations and lead to customer dissatisfaction.

5. Memory Fragmentation: Tenured space overflow can exacerbate memory fragmentation issues within the JVM heap. As memory becomes fragmented, it becomes harder for the JVM to allocate contiguous blocks of memory, leading to inefficiencies in memory usage and potentially worsening the tenured space overflow problem.

Simulating Tenured Space Overflow in MID Server

The Java program given below simulates tenured space overflow on any machine/container in which it’s launched.

import java.util.ArrayList;
import java.util.List;

public class TenuredSpaceOverflowExample {

    public static void main(String[] args) {
        List<byte[]> tenuredObjects = new ArrayList<>();

        try {
            while (true) {
                // Allocate 10MB of memory in each iteration
                tenuredObjects.add(new byte[10 * 1024 * 1024]);
                System.out.println("Allocated 10MB. Total memory used: " + (tenuredObjects.size() * 10) + "MB");
                
                try {
                    Thread.sleep(10); // Introduce a slight delay to observe the output
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } catch (OutOfMemoryError e) {
            System.out.println("OutOfMemoryError: JVM Tenured Space Overflow");
            e.printStackTrace();
        }
    }
}

The Java program provided is an example designed to demonstrate how memory allocations within the JVM can lead to an overflow of the Tenured Space, which is a component of the JVM’s heap memory where older objects reside. It does so by continuously creating large 10 MB byte arrays and adding them to a list, which simulates long-lived objects that would typically be moved to the Tenured Space after surviving garbage collection cycles in the Young Generation. The Thread.sleep introduces a delay allowing observation of memory consumption before system failure. As the loop has no termination condition, the list keeps growing, and the JVM heap is increasingly filled until it can no longer accommodate new objects, resulting in an OutOfMemoryError. However, whether the overflow occurs specifically in the Tenured Space depends on several JVM factors such as garbage collection policy, heap size settings, and the rate of object promotions from Young to Old Generation.

Tenured Space Overflow in ServiceNow MID Server

Let’s create a JAR (Java Archive) file from this program. You can create the JAR file by issuing the following command:

javac TenuredSpaceOverflowExample.java
jar cf TenuredSpaceOverflowExample.jar TenuredSpaceOverflowExample.class

Once a JAR file is created, let’s upload and run this program in the ServiceNow MID Server as documented in the MID Server setup guide. This guide provides a detailed walkthrough on how to run a custom Java application in the ServiceNow MID Server infrastructure. It walks through the following steps:

1. Creating a ServiceNow application
2. Installing MID Server on AWS EC2 instance
3. Configuring MID Server
4. Installing Java application within MID Server
5. Running Java application from MID server

We strongly encourage you to check out the guide if you are not sure on how to run custom Java applications in ServiceNow MID server infrastructure.

yCrash’s Tenured Space Overflow Diagnosis of the ServiceNow MID Server

yCrash is a powerful monitoring tool specifically designed to identify performance bottlenecks and provide actionable recommendations within the ServiceNow environment. ServiceNow organizations rely on yCrash extensively for diagnosing and resolving performance issues.

When facing tenured space overflow scenarios on ServiceNow’s MID Server, yCrash actively monitors the micro-metrics of the environment. It promptly detects instances of tenured space overflow and generates comprehensive reports on the dashboard, offering valuable insights into the impact on system performance. These insights empower ServiceNow administrators to implement effective measures to address tenured space overflow and optimize system efficiency.

yCrash presents an overview of issues related to tenured space overflow, providing users with a comprehensive view of specific areas requiring attention due to memory constraints.

The information suggests that a large portion of memory allocated for primitive arrays is not being used effectively, hinting at optimization possibilities within your application. The presence of an inefficient array consuming nearly 460 MB of memory indicates potential overallocation or underutilization. Addressing this inefficiency is crucial as it may prevent unnecessary memory consumption and the risk of encountering memory-related issues, such as tenured space overflow. By investigating and optimizing this arrays, you can potentially reclaim a significant amount of memory, which could improve the application’s performance. Detecting and resolving such inefficiencies is an essential step in memory management and helps maintain the health and scalability of your application.

The thread details suggest that the main Java thread is holding a large amount of memory in local variables, specifically in a single instance of an Object[] array. This indicates that long-lived objects in the array occupy the majority of the tenured space. Persistently accumulating such objects without proper garbage collection can lead to a tenured space overflow. The thread stack trace would typically reveal the allocation sites and potential memory leaks. Addressing this requires investigating why these objects are not being collected and optimizing memory management in the application. You can see the report here.

Conclusion

In summary, yCrash’s analysis of tenured space overflow provides valuable insights into memory-related issues within the application. The tool’s troubleshooting report and leak suspect view help identify potential causes of tenured space overflow, such as memory leaks or large objects. Additionally, the integration with the ServiceNow MID Server streamlines incident reporting and resolution processes, enhancing overall IT service management efficiency and contributing to a more stable and optimized IT environment. If you want to diagnose performance problems in your ServiceNow deployment using yCrash you may register here.