compare-revisions

Do you have a "staging" Kubernetes cluster and a "production" Kubernetes cluster and want to see what's deployed to staging, but not to production?

compare-revisions is a simple web service that you can deploy to your staging cluster that will tell you what's on staging but not on prod.

It does this by assuming that there exists a simple mapping from image names to Git repositories, and from image tags to Git revisions.

Example

This configuration will pull from a configuration repository on Github (my-org/service-config) every minute and compare the images found under the k8s/dev path to the corresponding images in the k8s/prod path.

When it finds weaveworks/cortex-distributor images, it will apply a regular expression to extract the revision from the image tag, assuming that the metric tag is of the form master-1ab2c3d.

It will then display the top-level (i.e. --first-parent) revisions from the Git log, including only those revisions that touch the given paths.

config-repo:
  url: git@github.com:my-org/service-config.git
  poll-interval: 1m
  source-env:
    name: dev
    path: k8s/dev
  target-env:
    name: prod
    path: k8s/prod

images:
  weaveworks/cortex-distributor:
    git-url: git@github.com:weaveworks/cortex.git
    image-to-revision-policy: weaveworks
    paths:
      - cmd/distributor
      - distributor
      - ring
      - util

revision-policies:
  weaveworks:
    type: regex
    match: ^master-([0-9a-f]+)$
    output: \1

How to build it

Prerequisites

• Run Linux or macOS
• Install Stack
• Install GNU Make

Building

You can either build with make:

make

which will also build a Docker image.

You can also build directly with stack via:

stack build

To build a Docker image, you must do:

stack image container

Or on macOS

stack --docker image container

in order to ensure the container has Linux binaries.

Note that the image generated by stack has a weird name.

To do a Dockerized build with make, do:

make STACK_FLAGS=--docker

How to run it

Natively

Build and install the code with stack install and then run with:

compare-revisions --port 8080 --config-file config.yaml --git-repo-dir /var/run/compare-revisions

This will start a server that you can reach at http://localhost:8080/

With Docker

Create a Docker image with:

make

The last line of successful make output will be the name of the image, e.g. compare-revisions:master-1a2b3cd.

You can then run the image like so:

docker run -ti -p 8080:80 -v /path/to/config:/data \
    compare-revisions:master-1a2b3cd \
      --port 80 \
      --config-file \
      /data/config.yaml

And you can reach the server at http://localhost:8080/ if you are running Docker natively. If you're on a Mac and using Docker Machine, you can run:

open http://$(docker-machine ip):8080/

To browse to the running server.