helmfile/docs/shared-configuration-across...

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# Shared Configuration Across Teams
Assume you have two or more teams, each work for a different internal or external service, like:
- Product 1
- Product 2
- Observability
The simplest `helmfile.yaml` that declares the whole cluster that is composed of the three services would look like the below:
```yaml
releases:
- name: product1-api
chart: product1-charts/api
# snip
- name: product1-web
chart: product1-charts/web
# snip
- name: product2-api
chart: saas-charts/api
# snip
- name: product2-web
chart: product2-charts/web
# snip
- name: observability-prometheus-operator
chart: stable/prometheus-operator
# snip
- name: observability-process-exporter
chart: stable/prometheus-operator
# snip
```
This works, but what if you wanted to a separate cluster per service to achieve a smaller blast radius?
Let's start by creating a `helmfile.yaml` for each service.
`product1/helmfile.yaml`:
```yaml
releases:
- name: product1-api
chart: product1-charts/api
# snip
- name: product1-web
chart: product1-charts/web
# snip
- name: observability-prometheus-operator
chart: stable/prometheus-operator
# snip
- name: observability-process-exporter
chart: stable/prometheus-operator
# snip
```
`product2/helmfile.yaml`:
```yaml
releases:
- name: product2-api
chart: product2-charts/api
# snip
- name: product2-web
chart: product2-charts/web
# snip
- name: observability-prometheus-operator
chart: stable/prometheus-operator
# snip
- name: observability-process-exporter
chart: stable/prometheus-operator
# snip
```
You will (of course!) notice this isn't DRY.
To remove the duplication of observability stack between the two helmfiles, create a "sub-helmfile" for the observability stack.
`observability/helmfile.yaml`:
```yaml
- name: observability-prometheus-operator
chart: stable/prometheus-operator
# snip
- name: observability-process-exporter
chart: stable/prometheus-operator
# snip
```
As you might have imagined, the observability helmfile can be reused from the two product helmfiles by declaring `helmfiles`.
`product1/helmfile.yaml`:
```yaml
helmfiles:
- ../observability/helmfile.yaml
releases:
- name: product1-api
chart: product1-charts/api
# snip
- name: product1-web
chart: product1-charts/web
# snip
```
`product2/helmfile.yaml`:
```yaml
helmfiles:
- ../observability/helmfile.yaml
releases:
- name: product2-api
chart: product2-charts/api
# snip
- name: product2-web
chart: product2-charts/web
# snip
```
## Using sub-helmfile as a template
You can go even further by generalizing the product related releases as a pair of `api` and `web`:
`shared/helmfile.yaml`:
```yaml
releases:
- name: product{{ env "PRODUCT_ID" }}-api
chart: product{{ env "PRODUCT_ID" }}-charts/api
# snip
- name: product{{ env "PRODUCT_ID" }}-web
chart: product{{ env "PRODUCT_ID" }}-charts/web
# snip
```
Then you only need one single product helmfile
`product/helmfile.yaml`:
```yaml
helmfiles:
- ../observability/helmfile.yaml
- ../shared/helmfile.yaml
```
Now that we use the environment variable `PRODUCT_ID` to as the parameters of release names, you need to set it before running `helmfile`, so that it produces the differently named releases per product:
```console
$ PRODUCT_ID=1 helmfile -f product/helmfile.yaml apply
$ PRODUCT_ID=2 helmfile -f product/helmfile.yaml apply
```