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Installing the KEDA HTTP Add On

The HTTP Add On is highly modular and, as expected, builds on top of KEDA core. Below are some additional components:

  • Operator - watches for ScaledHTTPObject CRD resources and creates necessary backing Kubernetes resources (e.g. Deployments, Services, ScaledObjects, and so forth)
  • Scaler - communicates scaling-related metrics to KEDA. By default, the operator will install this for you as necessary.
  • Interceptor - a cluster-internal proxy that proxies incoming HTTP requests, communicating HTTP queue size metrics to the scaler, and holding requests in a temporary request queue when there are not yet any available app Pods ready to serve. By default, the operator will install this for you as necessary.

There is pending work that may eventually make this component optional.

Before You Start: Cluster-global vs. Namespaced installation

Both KEDA and the HTTP Addon can be installed in either cluster-global or namespaced mode. In the former case, your ScaledObjects and HTTPScaledObjects (respectively) can be installed in any namespace, and one installation will detect and process it. In the latter case, you must install your ScaledObjects and HTTPScaledObjects in a specific namespace.

You have the option of installing KEDA and the HTTP Addon in either mode, but if you install one as cluster-global, the other must also be cluster-global. Similarly, if you install one as namespaced, the also must also be namespaced in the same namespace.

Installing KEDA

Before you install any of these components, you need to install KEDA. Below are simplified instructions for doing so with Helm, but if you need anything more customized, please see the official KEDA deployment documentation. If you need to install Helm, refer to the installation guide.

This document will rely on environment variables such as ${NAMESPACE} to indicate a value you should customize and provide to the relevant command. In the below helm install command, ${NAMESPACE} should be the namespace you'd like to install KEDA into. KEDA and the HTTP Addon provide scaling functionality to only one namespace per installation.

helm repo add kedacore https://kedacore.github.io/charts
helm repo update
helm install keda kedacore/keda --namespace ${NAMESPACE} --create-namespace

The above command installs KEDA in cluster-global mode. Add --set watchNamespace=<target namespace> to install KEDA in namespaced mode.

Install via Helm Chart

The Helm chart for this project is within KEDA's default helm repository at kedacore/charts, you can install it by running:

helm install http-add-on kedacore/keda-add-ons-http --namespace ${NAMESPACE}

The above command installed the HTTP Addon in cluster-global mode. Add --set operator.watchNamespace=<target namespace> to install the HTTP Addon in namepaced mode. If you do this, you must also install KEDA in namespaced mode and use the same target namespace.

Installing the HTTP add on won't affect any running workloads in your cluster. You'll need to install an HTTPScaledObject for each individual Deployment you want to scale. For more on how to do that, please see the walkthrough.

Customizing the Installation

There are a few values that you can pass to the above helm install command by including --set NAME=VALUE on the command line.

If you want to install the latest build of the HTTP Add on, set version to canary:

helm install http-add-on kedacore/keda-add-ons-http --create-namespace --namespace ${NAMESPACE} --set images.tag=canary

For an exhaustive list of configuration options, see the official HTTP Addon chart values.yaml file.

A Note for Developers and Local Cluster Users

Local clusters like Microk8s offer in-cluster image registries. These are popular tools to speed up and ease local development. If you use such a tool for local development, we recommend that you use and push your images to its local registry. When you do, you'll want to set your images.* variables to the address of the local registry. In the case of MicroK8s, that address is localhost:32000 and the helm install command would look like the following:

helm repo add kedacore https://kedacore.github.io/charts
helm repo update
helm pull kedacore/keda-add-ons-http --untar --untardir ./charts
helm upgrade kedahttp ./charts/keda-add-ons-http \
    --install \
    --namespace ${NAMESPACE} \
    --create-namespace \
    --set image=localhost:32000/keda-http-operator \
    --set images.scaler=localhost:32000/keda-http-scaler \
    --set images.interceptor=localhost:32000/keda-http-interceptor

Next Steps

Now that you're finished installing KEDA and the HTTP Add On, please proceed to the walkthrough to test out your new installation.