# 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 `HTTPScaledObject` CRD resources and creates necessary backing Kubernetes resources (e.g. `Deployment`s, `Service`s, `ScaledObject`s, 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 `Pod`s ready to serve. By default, the operator will install this for you as necessary.
    >There is [pending work](https://github.com/kedacore/http-add-on/issues/354) that may eventually make this component optional.

## Before You Start: Cluster-global vs. Namespaced Installation

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

You have the option of installing KEDA and the HTTP Add-on 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](https://helm.sh), but if you need anything more customized, please see the [official KEDA deployment documentation](https://keda.sh/docs/2.0/deploy/). If you need to install Helm, refer to the [installation guide](https://helm.sh/docs/intro/install/).

>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.

```console
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 the Add-on via Helm Chart

The Helm chart for this project is within KEDA's default helm repository at [kedacore/charts](http://github.com/kedacore/charts), you can install it by running:

```console
helm install http-add-on kedacore/keda-add-ons-http --namespace ${NAMESPACE}
```
>The above command installed the HTTP Add-on in cluster-global mode. Add `--set operator.watchNamespace=<target namespace>` to install the HTTP Add-on 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](./walkthrough.md).

### 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.

- `images.operator` - the name of the operator's Docker image, not including the tag. Defaults to [`ghcr.io/kedacore/http-add-on-operator`](https://github.com/kedacore/http-add-on/pkgs/container/http-add-on-operator).
- `images.scaler` - the name of the scaler's Docker image, not including the tag.  Defaults to [`ghcr.io/kedacore/http-add-on-scaler`](https://github.com/kedacore/http-add-on/pkgs/container/http-add-on-scaler).
- `images.interceptor` - the name of the interceptor's Docker image, not including the tag. Defaults to [`ghcr.io/kedacore/http-add-on-interceptor`](https://github.com/kedacore/http-add-on/pkgs/container/http-add-on-interceptor).
- `images.tag` - the tag to use for all the above docker images. Defaults to the [latest stable release](https://github.com/kedacore/http-add-on/releases).

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

```console
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 Add-on chart [values.yaml file](https://github.com/kedacore/charts/blob/master/http-add-on/values.yaml).

### A Note for Developers and Local Cluster Users

Local clusters like [Microk8s](https://microk8s.io/) 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:

```console
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
```

## Compatibility Table

| HTTP Add-On version | KEDA version      | Kubernetes version |
|---------------------|-------------------|--------------------|
| main                | v2.16             | v1.30 - v1.32      |
| 0.10.0              | v2.16             | v1.30 - v1.32      |
| 0.9.0               | v2.16             | v1.29 - v1.31      |
| 0.8.0               | v2.14             | v1.27 - v1.29      |
| 0.7.0               | v2.13             | v1.27 - v1.29      |
| 0.6.0               | v2.12             | v1.26 - v1.28      |
| 0.5.1               | v2.10             | v1.24 - v1.26      |
| 0.5.0               | v2.9              | v1.23 - v1.25      |

## Next Steps

Now that you're finished installing KEDA and the HTTP Add-on, please proceed to the [walkthrough](./walkthrough.md) to test out your new installation.

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