OutOfMemoryError Kill Process or Sacrifice Child 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: Kill Process or Sacrifice Child, which would disrupt entire Jenkins availability. In this post let’s discuss what does ‘java.lang.OutOfMemoryError: Kill Process or Sacrifice Child’ 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 Kill Process or Sacrifice Child in Jenkins

When Jenkins experience ‘java.lang.OutOfMemoryError: Kill Process or Sacrifice Child’ here are the options one can take to stabilize the Jenkins immediately (basically first-aid):

1. Restart the JVM: When ‘java.lang.OutOfMemoryError: Kill Process or Sacrifice Child’ happens in Jenkins, it will put 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. Terminate Unnecessary processes: This error happens when there is insufficient RAM capacity in the container/device in which Jenkins is running. Sometimes new cronjob or home-grown script will crop up & they will consume memory, which will leave less room for the Jenkins application to run. Terminate those newly cropped up processes, if they aren’t critical.

Why OutOfMemoryError Kill Process or Sacrifice Child Happens in Jenkins?

To better understand OutOfMemoryError Kill Process or Sacrifice Child, 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: Kill process (java) or sacrifice child’

java.lang.OutOfMemoryError: Kill Process or Sacrifice Child occurs in Jenkins when the host system runs critically low on RAM and the Linux OOM Killer steps in to forcefully terminate memory-consuming processes to free up resources. Unlike other OOME types which are thrown by the JVM itself, this one is triggered by the OS, and if the process the OOM Killer targets happens to be Jenkins, the result is an abrupt termination with no graceful shutdown, no heap dump, and no JVM-level warning.

This video covers OutOfMemoryError: Kill Process or Sacrifice Child from a Java perspective, the same underlying concept that applies to Jenkins.

Root Causes of OutOfMemoryError Kill Process or Sacrifice Child in Jenkins

‘java.lang.OutOfMemoryError: Kill Process or Sacrifice Child’ in Jenkins is potentially caused because of the following reasons:

1. More processes in the device: When a lot of other processes are running on the container/device, it leaves less memory for the Jenkins application to run.

2. Initial and Max Heap size set to different values: If initial heap size (i.e., -Xms) is configured at a lower value than the max heap size (i.e., -Xmx), then during runtime, Jenkins application’s memory size will grow. If there is a lack of RAM capacity during that growth time, the kernel will terminate the Java application throwing this error.

3. Native Memory region growing: In case the initial and max heap size is set to the same value, native memory region of the JVM can grow during the runtime. If native memory is growing and there is a lack of RAM capacity, then the kernel can terminate the Jenkins application by throwing this error 

How to Diagnose the OutOfMemoryError Kill Process or Sacrifice Child Problem in Jenkins (Step-by-Step)

In order to troubleshoot this problem and other Jenkins Production problems, you can leverage the yCrash monitoring tool. This tool is capable of predicting outages before it surfaces in the production environment. Once it predicts outage in the environment, it captures 360° troubleshooting artifacts from your environment, analyses them and instantly generates a root cause analysis report. Artifacts it captures include Garbage Collection log, Thread Dump, Heap Substitute, netstat, vmstat, iostat, top, top -H, dmesg, kernel parameters, disk usage…. 

You can register here and start using the free-tier of this tool.

Below is the report generated by the yCrash tool pointing that the Jenkins process has been terminated by analyzing the kernel log:

Fig: yCrash Tool pointing out OutOfMemoryError: Kill process (java) or sacrifice child

Solutions for OutOfMemoryError Kill Process or Sacrifice Child in Jenkins

Here are the potential solutions to address java.lang.OutOfMemoryError: Kill Process or Sacrifice Child 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 Kill Process or Sacrifice Child OutOfMemoryError started to surface after it, consider reverting to previous Jenkins installation. 
4. Increase RAM capacity: Try to run the Jenkins application on a container/device which has larger RAM capacity.
5. Reduce other processes: Terminate (or move) other  processes that are running on the container/device, so that there is enough memory for the Jenkins application to run.
6. Set initial Heap and Max Heap to same value: When you set the initial heap size (i.e. -Xms) and max heap size (-Xmx) to the same value, JVM will be allocated with maximum heap size right at the startup time. Thus, JVM’s memory allocation will not grow or shrink at runtime. Kernel typically terminates the application which is constantly demanding more memory. Thus, the kernel will not terminate the Jenkins application in the middle.

Note: Setting Initial and Max Heap size to the same value provides considerable benefits such as: Increased application availability, better performance, better Garbage Collection behaviour, faster startup time, … Learn more about the benefits of setting initial and max heap size to same value.

7. Fix Leak in Native Memory: Sometimes there could be a leak in the Native Memory as well. There could be a thread leak, or direct buffer leak – which can cause increased memory consumption. Instrument proper fix to arrest those leaks.

How to Prevent OutOfMemoryError Kill Process or Sacrifice Child 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 at 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: Kill Process or Sacrifice Child’ 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.