Memory saturation occurs in pods after cluster upgrade to Kubernetes 1.25
This article discusses how to fix pods that stop working because of memory saturation or out-of-memory (OOM) errors that occur after you upgrade a Microsoft Azure Kubernetes Service (AKS) cluster to Kubernetes 1.25.x.
Symptoms
One or more of the following issues occur:
Memory pressure on nodes
Increased memory usage for apps when compared to their memory usage before the upgrade
CPU throttling on nodes
Pod failure because of OOM errors
Performance degradation can occur in apps that run in the following environments:
- Java Runtime Environment (JRE) (for JRE versions that are earlier than version 11.0.18 or version 1.8.0 372)
- .NET versions that are earlier than version 5.0
- Node.js
Note
This list of environments in which performance degradation can occur isn't a comprehensive list. There might be other environments that experience memory saturation or OOM issues.
Solution
Beginning in the release of Kubernetes 1.25, the cgroup version 2 API has reached general availability (GA). AKS now uses Ubuntu Linux version 22.04. By default, version 22.04 uses cgroup version 2 API. To make sure the cgroup version 2 API is available for use in other environments to prevent the memory saturation issue, follow this guidance:
If you run Java applications, upgrade to a Java version that supports cgroup version 2 and follow the guidance in Containerize your Java applications. You might be able to update the base image in certain versions in which the fix has been backported. Use a version or framework that natively supports cgroup version 2. For Azure customers, Microsoft officially supports Eclipse Temurin binaries (Java 8) and Microsoft Build of OpenJDK binaries (Java 11+).
Similarly, if you're using .NET, upgrade to .NET version 5.0 or a later version.
In addition, to enable pods to use more resources, increase their memory requests and limits.
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