OutOfMemoryError Permgen space in Jenkins: Root Causes, Diagnostics & Production Fixes

Jenkins – popular CI/CD pipeline is used for several critical operations in the organization such as building applications, conducting automated tests, deployments in pre-prod and prod environments, … If Jenkins is down, engineers’ productivity will be severely hampered. Thus, extra care is given to major organizations to keep them up 24 x 7. 

While Java has 9 types of OutOfMemoryError, Jenkins is susceptible to 8 of them. In this blog series, we systematically walk through each of those 8 types, helping you identify, diagnose, and fix them. This post covers one of them.

Occasionally it can experience java.lang.OutOfMemoryError: Permgen space, which would disrupt entire Jenkins availability. In this post let’s discuss what does ‘java.lang.OutOfMemoryError: Permgen space’ mean, how to isolate the root cause of it quickly, what are its temporary and permanent fixes, and even better how to prevent them from happening.

Immediate Stabilization Steps – OutOfMemoryError Permgen space in Jenkins 

When Jenkins experience ‘java.lang.OutOfMemoryError: Permgen space’ here are the options one can take to stabilize the Jenkins immediately (basically first-aid):

1. Restart the JVM: When ‘java.lang.OutOfMemoryError: Permgen space’ happens in Jenkins, it will put the JVM into an unstable state. It’s dangerous to run Jenkins in this setting, as it can result in erroneous behavior. Thus, it’s highly recommended to restart the JVM, so that it will come back in a clean slate.

2. Increase PermGen size: ‘java.lang.OutOfMemoryError: Permgen space’ happens in Jenkins due to lack of space in the Permgen region of the JVM Memory. Thus increase the Permgen memory region size. You can increase the Permgen memory region by passing following arguments to your JVM: 

-XX:MaxPermSize=<size> Sets the upper limit for Permgen space 

–XX:PermSize=<size> Sets the initial threshold that triggers the first Garbage Collection (GC) for Permgen space.

Why OutOfMemoryError Permgen space Happens in Jenkins?

To better understand OutOfMemoryError Permgen space, we first need to understand different JVM Memory regions. Here is a video clip that gives a good introduction about different JVM memory regions. But in nutshell, JVM has following memory regions:

Fig: JVM Memory Regions

1. Young Generation: Newly created application objects are stored in this region.
2. Old Generation: Application objects that are living for longer duration are promoted from the Young Generation to the Old Generation. Basically this region holds long lived objects.
3. Metaspace: Class definitions, method definitions and other metadata that are required to execute your program are stored in the Metaspace region. This region was added in Java 8. Before that metadata definitions were stored in the PermGen. Since Java 8, PermGen was replaced by Metaspace.
4. Threads: Each application thread requires a thread stack. Space allocated for thread stacks, which contain method call information and local variables are stored in this region.
5. Code Cache: Memory areas where compiled native code (machine code) of methods is stored for efficient execution are stored in this region.
6. Direct Buffer: ByteBuffer objects are used by modern framework (i.e. Spring WebClient) for efficient I/O operations. They are stored in this region.
7. GC (Garbage Collection): Memory required for automatic garbage collection to work is stored in this region. 
8. JNI (Java Native Interface): Memory for interacting with native libraries and code written in other languages are stored in this region.
9. misc: There are areas specific to certain JVM implementations or configurations, such as the internal JVM structures or reserved memory spaces, they are classified as ‘misc’ regions.

Fig: ‘java.lang.OutOfMemoryError: Permgen space’

java.lang.OutOfMemoryError: PermGen Space occurs in Jenkins when the number of class definitions, method definitions, and metadata loaded into the Permanent Generation region exceeds the memory limit set by -XX:PermSize. In a Jenkins environment, this is commonly driven by the sheer volume of plugins, custom build scripts, and pipeline libraries that continuously load new classes into PermGen, and unlike heap objects, these are rarely unloaded during normal operation, causing the region to fill up over time. 

This video covers OutOfMemoryError: Permgen space from a Java perspective, the same underlying concept that applies to Jenkins.

Root Causes of OutOfMemoryError Permgen space in Jenkins 

‘java.lang.OutOfMemoryError: Permgen space’ in Jenkins is potentially caused because of the following reasons:

1. Creating large number of dynamic classes: If your Jenkins plugins uses JavaScript/Groovy kind of scripting languages or Java Reflection to create new classes at runtime. 

2. Loading large number of classes: Either your Jenkins installation itself has a lot of classes, or it uses a lot of 3rd party plugins/libraries which have a lot of classes in it.

3. Loading large number of class loaders: Your Jenkins installation or the 3rd party plugins is loading a lot of class loaders.

How to Diagnose the OutOfMemoryError Permgen space Problem in Jenkins (Step-by-Step)

To diagnose OutOfMemoryError: PermGen Space in Jenkins, we need to inspect the contents of the PermGen region. Upon inspecting the contents, you can figure out which Jenkins plugin, build script, or pipeline library is driving the leak.

-verbose:class: If you are running Jenkins on Java version 8 or below, you can use this option. When you pass -verbose:class to Jenkins during startup, it will print all the classes being loaded into memory. These loaded classes will appear in the standard error stream — visible in the Jenkins console output, provided you are not routing the error stream to a separate log file. Example:

java {app_name} -verbose:class

If you are still unable to determine the origin of the leak based on the class names, you can do a deeper investigation by capturing a heap dump from Jenkins. Once the heap dump is captured from Jenkins, load it into a tool like HeapHero, JHat, or Eclipse MAT to analyze it. These tools will help identify which classes are accumulating in Jenkins’ PermGen and point you toward the offending plugin or custom code that is holding them in memory.

Solutions for OutOfMemoryError Permgen space in Jenkins 

Here are the potential solutions to address java.lang.OutOfMemoryError: Permgen space in Jenkins:

1. Identify & Fix the Memory Leak in Jenkins: Using the diagnostic steps described in the above section find the leaking objects in the memory and fix it.

2. Remove the recently added Plugins: Whenever you add new plugins, it will occupy space in the Metaspace. Sometimes you might end up adding poorly implemented, memory inefficient plugins. Remove the recently added plugins and restart the JVM and see whether Jenkins stabilizes. 

3. Revert to Previous Jenkins Installation: If you have recently upgraded to latest version of Jenkins installation and Permgen space OutOfMemoryError started to surface after it, consider reverting to previous Jenkins installation. 

4. Increase PermGen size: ‘java.lang.OutOfMemoryError: Permgen space’ happens in Jenkins due to lack of space in the Permgen region of the JVM Memory. Thus increase the Permgen memory region size. You can increase the Permgen memory region by passing following arguments to your JVM: 

-XX:MaxPermSize=<size> Sets the upper limit for Permgen memory region

–XX:PermSize=<size> Sets the initial threshold that triggers the first Garbage Collection (GC) for Permgen memory region.

How to Prevent OutOfMemoryError Permgen space in Jenkins

Before you upgrade to new release of Jenkins or install a new Jenkins plugin in the production environment, you might be studying following key metrics in your performance lab:

• CPU Utilization
• Memory Utilization
• Response Time of key transactions

These are wonderful metrics that highlight the performance characteristics of the new release. However, several performance problems slowly build over the period of time, for example for most applications OutOfMemoryError happens only if it runs for more than 1 week. In the performance lab, we don’t run such long endurance tests. 

Above mentioned metrics are more reactive indicators that don’t indicate the silently lurking problem in the environment. We recommend studying below mentioned Micro-metrics along with above reactive indicators in the performance lab and certify the release. These Micro-Metrics are good are predicting/forecasting performance problems even if they act at acute scale.

• GC Behavior Pattern: Detects memory leaks, poor GC configuration, or excessive object promotion causing GC pauses.
• Object Creation Rate: Identifies allocation surges that can trigger frequent GCs or memory pressure.
• GC Throughput: Highlights apps spending too much time in GC instead of work—can lead to CPU spikes or slowdowns.
• GC Pause Time: Surfaces stop-the-world GC events affecting responsiveness or causing thread backlogs.
• Thread Patterns: Flags CPU spikes, thread starvation, bursty load, and thread buildup from backend slowness.
• Thread States: Detects BLOCKED, DEADLOCKED, or WAITING threads due to DB chattiness, config limits, or locking.
• Thread Pool Behavior: Identifies thread exhaustion, request rejections, or poor pooling thresholds in backend services.
• TCP/IP Connection Count & States: Catches backend connection leaks, TIME_WAIT surges, or slow/unresponsive downstream services.
• Error Trends in Application Logs: Detects hidden runtime errors, JDBC leaks, logging misconfigurations, or disk issues.

yCrash tool facilitates you reporting these Micro-Metrics which will unearth several performance problems well in advance, before they silently surface in production. You can find the details on how to source and study these Micro-Metrics through yCrash from here. 

Business Impact & ROI

Isolating and fixing OutOfMemoryError in Jenkins will have considerable business impact to your organization:

1. Engineering Time Savings: yCrash dramatically reduces the time engineers spend analyzing Heap Dumps and pinpointing root causes in complex, multi-threaded applications.
   • Suppose your organization is analyzing 10 incidents per month & each analysis traditionally will take around 40 hours. 
   • With a Performance Engineer’s hourly rate at USD $100, yCrash can save approximately $480,000 annually (10 incidents x 40 hours/dump x $100/hour x 12 months) by automating root cause analysis and reducing troubleshooting time.

2. Rapid Deployments & Increased Productivity: yCrash minimizes prolonged downtime of Jenkins that can lead to delayed deployment, degeneration of engineers productivity and reputational damage of the organization. By quickly diagnosing issues, yCrash helps to prevent such large-scale impacts, protecting revenue and brand reputation.

3. Protection from Escalated Operational Consequences: Certain Jenkins outages can have severe repercussions, including escalated consequences like organizational changes or job losses. yCrash’s rapid problem isolation capabilities prevent such disruptions, allowing teams to resolve issues before they escalate to crisis levels. By maintaining operational continuity and team stability, yCrash supports a steady, resilient organizational environment and protects against the high stakes impacts that can result from unmanaged production outages.

Conclusion

Jenkins is the backbone of your organization’s CI/CD pipeline. Keeping it stable is not optional, it’s rather essential. Even though ‘java.lang.OutOfMemoryError: Permgen space’ is not a common error, it can hurt your entire Jenkins platform availability, when it surfaces. Hopefully this post has given you enough light on how to troubleshoot this problem effectively & efficiently.