added README.md for new Ditto Helm chart specifying configuration options

Signed-off-by: Thomas Jäckle <[email protected]>

Author: thjaeckle

deployment/helm/README.md

@@ -0,0 +1,20 @@
+# Eclipse Ditto :: Helm
+
+The official Ditto Helm chart is managed here, in folder [ditto](ditto/).  
+It is deployed as "OCI artifact" to Docker Hub at: https://hub.docker.com/r/eclipse/ditto
+
+## Install Ditto via Helm Chart
+
+To install the chart with the release name eclipse-ditto, run the following commands:
+
+```shell script
+helm install -n ditto my-ditto oci://registry-1.docker.io/eclipse/ditto --version <version> --wait
+```
+
+# Uninstall the Helm Chart
+
+To uninstall/delete the `my-ditto` deployment:
+
+```shell script
+helm uninstall my-ditto
+```

deployment/helm/ditto/README.md

@@ -1,49 +1,137 @@
-# Eclipse Ditto :: Helm
+# Eclipse Ditto
 
-The Ditto Helm chart sources are managed here.
+## Introduction
 
-## Install Ditto via Helm Chart
+[Eclipse Ditto™](https://www.eclipse.org/ditto/) is a technology in the IoT implementing a software pattern
+called “digital twins”. A digital twin is a virtual, cloud based, representation of his real world counterpart
+(real world “Things”, e.g. devices like sensors, smart heating, connected cars, smart grids, EV charging stations, …).
 
-To install the chart with the release name eclipse-ditto, run the following commands:
+This chart uses `eclipse/ditto-XXX` containers to run Ditto inside Kubernetes.
 
-```shell script
-helm repo add eclipse-iot https://www.eclipse.org/packages/charts/
-helm repo update
-helm install eclipse-ditto eclipse-iot/ditto
+## Prerequisites
+
+Installing Ditto using the chart requires the Helm tool to be installed as described on the
+[IoT Packages chart repository prerequisites](https://www.eclipse.org/packages/prereqs/) page.
+
+TL;DR:
+
+* have a correctly configured [`kubectl`](https://kubernetes.io/docs/tasks/tools/#kubectl) (either against a local or remote k8s cluster)
+* have [Helm installed](https://helm.sh/docs/intro/)
+
+The Helm chart is being tested to successfully install on the three most recent Kubernetes versions.
+
+## Installing the Chart
+
+The instructions below illustrate how Ditto can be installed to the `ditto` namespace in a Kubernetes cluster using
+release name `eclipse-ditto`.  
+The commands can easily be adapted to use a different name space or release name.
+
+The target name space in Kubernetes only needs to be created if it doesn't exist yet:
+
+```bash
+kubectl create namespace ditto
 ```
 
-# Uninstall the Helm Chart
+The chart can then be installed to name space `ditto` using release name `my-ditto`:
 
-To uninstall/delete the eclipse-ditto deployment:
+```bash
+helm install --dependency-update -n ditto my-ditto oci://registry-1.docker.io/eclipse/ditto --version <version> --wait
+```
+
+
+## Uninstalling the Chart
+
+To uninstall/delete the `my-ditto` release:
 
-```shell script
-helm delete eclipse-ditto
+```bash
+helm uninstall -n ditto my-ditto
 ```
 
-# Working locally with the chart
+The command removes all the Kubernetes components associated with the chart and deletes the release.
 
-In order to test / develop the chart locally, this section should be of help.
+## Configuration
 
-## Testing templating
-For that, no running k8s cluster is necessary - the output will be the rendered k8s deployment descriptors:
+Please view the `values.yaml` for the list of possible configuration values with its documentation.
 
-```shell
-helm template my-ditto . -f values.yaml -f local-values.yaml --debug
+Specify each parameter using the `--set key=value[,key=value]` argument to `helm install`. For example:
+
+```bash
+helm install -n ditto my-ditto oci://registry-1.docker.io/eclipse/ditto --version <version> --set swaggerui.enabled=false
 ```
 
-## Installation
-To install the Ditto chart with the name `"my-ditto"`, perform:
+Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart.
+
+## Chart configuration options
+
+Please consult the [values.yaml](https://github.com/eclipse-ditto/ditto/blob/master/deployment/helm/ditto/values.yaml) 
+for all available configuration options of the Ditto Helm chart.  
+
+### Scaling options
 
-```shell
-helm install -f values.yaml -f local-values.yaml my-ditto . --wait
-kubectl port-forward svc/my-ditto-nginx 8080:8080
+Please note the defaults the chart comes with:
+* the default deploy 1 instance per Ditto service
+* each Ditto service is configured to require:
+  * 0.5 CPUs
+  * 1024 MiB of memory
+
+Adjust this to your requirements, e.g. scale horizontally by configuring a higher `replicaCount` or vertically by 
+configuring more resources.
+
+## Advanced configuration options
+
+Even more configuration options, not exposed to the `values.yaml`, can be configured using either environment variables
+or Java "System properties".  
+To inspect all available configuration options, please inspect Ditto's service configurations:
+
+* [policies.conf](https://github.com/eclipse-ditto/ditto/blob/master/policies/service/src/main/resources/policies.conf)
+* [things.conf](https://github.com/eclipse-ditto/ditto/blob/master/things/service/src/main/resources/things.conf)
+* [things-search.conf](https://github.com/eclipse-ditto/ditto/blob/master/thingsearch/service/src/main/resources/search.conf)
+* [connectivity.conf](https://github.com/eclipse-ditto/ditto/blob/master/connectivity/service/src/main/resources/connectivity.conf)
+* [gateway.conf](https://github.com/eclipse-ditto/ditto/blob/master/gateway/service/src/main/resources/gateway.conf)
+
+
+### Configuration via environment variables
+
+In order to provide an environment variable config overwrite, simply put the environment variable in the `extraEnv` 
+of the Ditto service you want to specify the configuration for.
+
+E.g. if you want to configure the `LOG_INCOMING_MESSAGES` for the `things` service to be disabled:  
+```yaml
+things:
+  # ...
+  extraEnv:
+    - name: LOG_INCOMING_MESSAGES
+      value: "false"
 ```
 
-Now, you can access Ditto on [http://localhost:8080](http://localhost:8080) - have fun.
+### Configuration via system properties
+
+Not all Ditto/Akka configuration options have an environment variable overwrite defined in the configuration.  
+For configurations without such an environment variable overwrite, the option can be configured via Java system property.  
+The documentation on how this works can be found in the 
+[HOCON documentation](https://github.com/lightbend/config/blob/main/HOCON.md#conventional-override-by-system-properties),
+which is the configuration format Ditto uses.
+
+E.g. if you want to would like to adjust the `journal-collection` name which the `things` service uses to write its
+journal entries to MongoDB (which can be found [here](https://github.com/eclipse-ditto/ditto/blob/33a38bc04b47d0167ba0e99fe76d96a54aa3d162/things/service/src/main/resources/things.conf#L268)),
+simply configure:
+
+
+```yaml
+things:
+  # ...
+  systemProps:
+    - "-Dakka-contrib-mongodb-persistence-things-journal.overrides.journal-collection=another_fancy_name"
+```
+
+
+## Troubleshooting
 
-## Uninstallation
-To uninstall the chart again, perform:
+If you experience high resource consumption (either CPU or RAM or both), you can limit the resource usage by
+specifying resource limits.
+This can be done individually for each single component.
+Here is an example how to limit CPU to 0.25 Cores and RAM to 512 MiB for the `connectivity` service:
 
-```shell
-helm uninstall my-ditto
+```bash
+helm upgrade -n ditto eclipse-ditto . --install --set connectivity.resources.limits.cpu=0.25 --set connectivity.resources.limits.memory=512Mi
 ```