Customizing Linkerd's Configuration with Kustomize
Instead of forking the Linkerd install and upgrade process,
Kustomize can be used to patch the output of linkerd install
in a consistent way. This allows customization of the install to add
functionality specific to installations.
To get started, save the output of linkerd install
to a YAML file. This will
be the base resource that Kustomize uses to patch and generate what is added
to your cluster.
linkerd install > linkerd.yaml
Next, create a kustomization.yaml
file. This file will contain the
instructions for Kustomize listing the base resources and the transformations to
do on those resources. Right now, this looks pretty empty:
resources:
- linkerd.yaml
Now, let’s look at how to do some example customizations.
Add PriorityClass
There are a couple components in the control plane that can benefit from being
associated with a critical PriorityClass
. While this configuration isn’t
currently supported as a flag to linkerd install
, it is not hard to add by
using Kustomize.
First, create a file named priority-class.yaml
that will create define a
PriorityClass
resource.
apiVersion: scheduling.k8s.io/v1
description: Used for critical linkerd pods that must run in the cluster, but
can be moved to another node if necessary.
kind: PriorityClass
metadata:
name: linkerd-critical
value: 1000000000
Next, create a file named patch-priority-class.yaml
that will contain the
overlay. This overlay will explain what needs to be modified.
apiVersion: apps/v1
kind: Deployment
metadata:
name: linkerd-identity
namespace: linkerd
spec:
template:
spec:
priorityClassName: linkerd-critical
Then, add this as a strategic merge option to kustomization.yaml
:
resources:
- priority-class.yaml
- linkerd.yaml
patchesStrategicMerge:
- patch-priority-class.yaml
Applying this to your cluster requires taking the output of kustomize
and piping it to kubectl apply
. For example, you can run:
# install the Linkerd CRDs
linkerd install --crds | kubectl apply -f -
# install the Linkerd control plane manifests using Kustomize
kubectl kustomize . | kubectl apply -f -