helm-s3-proxy

helm-s3-proxy

A HTTP compatible read proxy for the helm-s3 plugin.

Problem

You are currently using the helm s3 plugin to store your helm charts, but now need to migrate to a helm setup that requires pulling charts from helm's native HTTP. For us, this was the migration to flux 2.0. The solution is to install and use this proxy, which allows both options at the same time.

How it works

In our setup, we have dozens of helm repositories inside our s3 bucket: one per chart. This is because the index.yaml helm uses grows too large for all our helm charts for our current CI/CD system. Our S3 bucket looks something like this (but imagine dozens of chart names):

s3://company-bucket/chart1/index.yaml
s3://company-bucket/chart1/chart1-0.0.1.tgz
s3://company-bucket/chart2/index.yaml
s3://company-bucket/chart2/chart2-0.0.1.tgz
s3://company-bucket/chart2/chart2-0.0.2.tgz

One of the index files, s3://company-bucket/chart2/index.yaml, may look like this

apiVersion: v1
entries:
  chart2:
  - apiVersion: v2
    name: chart2
    urls:
    - s3://company-bucket/chart2/chart2-0.0.1.tgz
    version: 0.0.1
  - apiVersion: v2
    name: chart2
    type: application
    urls:
    - s3://company-bucket/chart2/chart2-0.0.2.tgz
    version: 0.0.2
generated: "2021-08-15T13:22:44.39851397Z"

The proxy will expose an endpoint, /chart2/index.yaml, that returns the following file (notice how it also changes the urls part)

apiVersion: v1
entries:
  chart2:
  - apiVersion: v2
    name: chart2
    urls:
    - http://helm-s3-proxy.helm-s3-proxy.svc.cluster.local/chart2/chart2-0.0.1.tgz
    version: 0.0.1
  - apiVersion: v2
    name: chart2
    type: application
    urls:
    - http://helm-s3-proxy.helm-s3-proxy.svc.cluster.local/chart2/chart2-0.0.2.tgz
    version: 0.0.2
generated: "2021-08-15T13:22:44.39851397Z"

We then configure flux2 to fetch helm charts from the proxy:

apiVersion: source.toolkit.fluxcd.io/v1beta1
kind: HelmRepository
metadata:
  name: chart2
spec:
  interval: 1m0s
  url: http://helm-s3-proxy.helm-s3-proxy.svc.cluster.local/chart2

Pre install

You will need an IAM role that can read files from your S3 bucket. Pass this role to the helm-s3-proxy service account. For an example, check out install below.

Install

Here is our flux2 configuration for installing the helm-s3-proxy

apiVersion: source.toolkit.fluxcd.io/v1beta1
kind: HelmRepository
metadata:
  name: helm-s3-proxy
  namespace: helm-s3-proxy
spec:
  interval: 1m0s
  url: https://cresta.github.io/helm-s3-proxy/
---
apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: helm-s3-proxy
  namespace: helm-s3-proxy
spec:
  chart:
    spec:
      chart: helm-s3-proxy
      sourceRef:
        kind: HelmRepository
        name: helm-s3-proxy
      version: 0.1.8
  interval: 1m0s
  releaseName: helm-s3-proxy
  values:
    s3_bucket: our-helm-bucket-name
    replace_http_path: http://helm-s3-proxy.helm-s3-proxy.svc.cluster.local
    serviceAccount:
      annotations:
        eks.amazonaws.com/role-arn: arn:aws:iam::${cluster_account_id}:role/${cluster_env}-eks-helm-bucket-read-role

Implementation notes

The proxy will cache the contents of index.yaml and their E-tag: requests to S3 return NotModified if the e-tag is the same. This allows us to speed up the more frequent index.yaml fetches.