How do you limit the amount of memory available to a container?

Introduction

Docker provides the ability to limit the amount of memory available to a container. This feature is crucial for managing resources effectively, especially when running multiple containers on a single host.

Problem

Without memory limits, a container can consume as much memory as the host allows, potentially leading to resource exhaustion. This can affect the performance of other containers and the host itself.

Solution

You can limit the amount of memory available to a container in Docker by using the --memory or -m option when running the container. The value of this option can be specified in bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), or terabytes (TB).

For example, to limit a container to 512 MB of memory, you can use the following command:

docker run --memory=512m my-image

Alternatively, you can specify the maximum amount of memory the container can use as a percentage of the total memory available on the host using the --memory-reservation or -m option.

For example, to limit a container to 50% of the total memory available on the host, you can use the following command:

docker run --memory-reservation=50% my-image

Discussion

Note that if the container exceeds the memory limit, it will be killed and the container’s exit status will be 137. Therefore, it’s important to set appropriate memory limits that balance resource usage and application requirements. Regular monitoring and adjustment of these limits can help ensure optimal performance.