k8s-keepalive

Introduction

Over time I've found myself needing a way to keep a k8s pod alive either for debugging purposes or for interactive use.

The typical recommendation on the internet is to use tail -f /dev/null or /usr/bin/sleep infinity.

I've found a few issues with these two approaches:

1. Both of those commands assume you have tail or sleep available in your image.
2. If you don't have tail or sleep you probably need a package manager to install them.
3. Unless you're careful, a package manager means more than just a single binary ending up in the image layer.
4. Depending on configuration, tail and sleep dont respect SIGINT making killing the container annoying.
5. There is no way robust way to configure Liveliness, Startup, or Readiness probes with tail and sleep.

This binary attempts to solve all of the aforementioned challenges. The binary is written in golang and is statically linked, making it compatible with a wide range of environments.

Additional features

For health checking you can point to :5000/ or :5000/healthz to recieve a 200 OK. You can also type any valid HTTP status code after the / to recieve that status code back.

Example: :5000/404 will send back a 404 in the response header and body.

Usage

Installation options

Run

To run it standalone:

docker run -p 8080:5000 mikecallahan/k8s-keepalive:1.0.0

Copy the binary

Download the latest release, COPY it into your Dockerfile, and use it in your ENTRYPOINT [""] or CMD [""] when you need it.

Public image

Use the public image in a multi-stage build:

FROM mikecallahan/k8s-keepalive:1.0.0 as build

--your docker file starts here ---
FROM ...
COPY --from=build /usr/bin/k8s-keepalive /usr/bin/k8s-keepalive

Update a yaml file

If you have an existing image already deployed in k8s, and your image has wget or curl, update your deployment.yaml:

spec:
  containers:
  - name: my-existing-container
    image: ubuntu:latest
    command: ["/bin/sh"]
    args: ["-c", "curl -OL https://github.com/mike-callahan/k8s-keepalive/releases/download/v1.0.0/k8s-keepalive && ./k8s-keepalive"]

Roadmap

• Keep container running
• Support health checks
• Statically link binary (net package)
• Release Dockerfile and image
• Support native SIGINT and SIGTERM
• Cross-compile for Windows