Open Source Summit + AI_dev Japan 2024

Modern applications increasingly require the output of large files such as videos and images, and the generation of more comprehensive logs. As a result, the use of RAM disks - ephemeral disks backed by memory, which are faster than traditional HDDs and SSDs - has become more common. In Kubernetes, RAM disks can be utilized through the abstraction of memory-backed emptyDir, which is based on tmpfs. However, if used carelessly, memory-backed emptyDir can pose significant risks to the stability of the Kubernetes cluster. When used as storage, the use case differs from typical memory usage by applications. Sharing files between different applications can obscure the responsibility for file garbage collection, increasing the risk of files not being deleted. If tmpfs usage excessively consumes node memory, the application containers using this tmpfs may be killed. In some cases, the deletion of tmpfs might not be timely, leading to memory exhaustion and potentially causing node crashes. This talk will share risk mitigation strategies for node crashes from the perspectives of cluster administrators, namespace administrators, and application developers.