docs: Add fully-local developer workflow and traps

docs/developer-guide/running-locally.md

@@ -1,14 +1,14 @@
-# Running ArgoCD locally
+# Running Argo CD locally
 
-## Run ArgoCD outside of Kubernetes
+## Run Argo CD outside of Kubernetes
 
-During development, it might be viable to run ArgoCD outside of a Kubernetes cluster. This will greatly speed up development, as you don't have to constantly build, push and install new ArgoCD Docker images with your latest changes.
+During development, it might be viable to run Argo CD outside of a Kubernetes cluster. This will greatly speed up development, as you don't have to constantly build, push and install new Argo CD Docker images with your latest changes.
 
-You will still need a working Kubernetes cluster, as described in the [Toolchain Guide](toolchain-guide.md), where ArgoCD will store all of its resources and configuration.
+You will still need a working Kubernetes cluster, as described in the [Toolchain Guide](toolchain-guide.md), where Argo CD will store all of its resources and configuration.
 
-If you followed the [Toolchain Guide](toolchain-guide.md) in setting up your toolchain, you can run ArgoCD locally with these simple steps:
+If you followed the [Toolchain Guide](toolchain-guide.md) in setting up your toolchain, you can run Argo CD locally with these simple steps:
 
-### Install ArgoCD resources to your cluster
+### Install Argo CD resources to your cluster
 
 First push the installation manifest into argocd namespace:
 
@@ -17,9 +17,9 @@ kubectl create namespace argocd
 kubectl apply -n argocd --force -f manifests/install.yaml
 ```
 
-### Scale down any ArgoCD instance in your cluster
+### Scale down any Argo CD instance in your cluster
 
-Make sure that ArgoCD is not running in your development cluster by scaling down the deployments:
+Make sure that Argo CD is not running in your development cluster by scaling down the deployments:
 
 ```shell
 kubectl -n argocd scale statefulset/argocd-application-controller --replicas 0
@@ -31,7 +31,7 @@ kubectl -n argocd scale deployment/argocd-applicationset-controller --replicas 0
 kubectl -n argocd scale deployment/argocd-notifications-controller --replicas 0
 ```
 
-### Start local services
+### Start local services (virtualized toolchain inside Docker)
 
 The started services assume you are running in the namespace where Argo CD is installed. You can set the current context default namespace as follows:
 
@@ -45,12 +45,101 @@ When you use the virtualized toolchain, starting local services is as simple as
 make start
 ```
 
-This will start all ArgoCD services and the UI in a Docker container and expose the following ports to your host:
+This will start all Argo CD services and the UI in a Docker container and expose the following ports to your host:
 
-* The ArgoCD API server on port 8080
-* The ArgoCD UI server on port 4000
+* The Argo CD API server on port 8080
+* The Argo CD UI server on port 4000
+* The Helm registry server on port 5000
 
-You can now use either the web UI by pointing your browser to `http://localhost:4000` or use the CLI against the API at `http://localhost:8080`. Be sure to use the `--insecure` and `--plaintext` options to the CLI.
+You may get an error listening on port 5000 on macOS:
+
+```text
+docker: Error response from daemon: Ports are not available: exposing port TCP 0.0.0.0:5000 -> 0.0.0.0:0: listen tcp 0.0.0.0:5000: bind: address already in use.
+```
+
+In that case, you can disable "AirPlay Receiver" in macOS System Preferences.
+
+You can now use either the web UI by pointing your browser to `http://localhost:4000` or use the CLI against the API at `http://localhost:8080`. Be sure to use the `--insecure` and `--plaintext` options to the CLI. Webpack will take a while to bundle resources initially, so the first page load can take several seconds or minutes.
+
+As an alternative to using the above command line parameters each time you call `argocd` CLI, you can set the following environment variables:
+
+```bash
+export ARGOCD_SERVER=127.0.0.1:8080
+export ARGOCD_OPTS="--plaintext --insecure"
+```
+
+### Start local services (running on local machine)
+
+The `make start` command of the virtualized toolchain runs the build and programs inside a Docker container using the test tools image. That makes everything repeatable, but can slow down the development workflow. Particularly on macOS where Docker and the Linux kernel run inside a VM, you may want to try developing fully locally.
+
+Docker should be installed already. Assuming you manage installed software using [Homebrew](https://brew.sh/), you can install other prerequisites like this:
+
+```sh
+# goreman is used to start all needed processes to get a working Argo CD development
+# environment (defined in `Procfile`)
+brew install goreman
+
+# You can use `kind` to run Kubernetes inside Docker. But pointing to any other
+# development cluster works fine as well as long as Argo CD can reach it.
+brew install kind
+```
+
+To set up Kubernetes, you can use kind:
+
+```sh
+kind create cluster --kubeconfig ~/.kube/config-kind
+
+# The started services assume you are running in the namespace where Argo CD is
+# installed. Set the current context default namespace.
+export KUBECONFIG=~/.kube/config-kind
+kubectl config set-context --current --namespace=argocd
+```
+
+Follow the above sections "Install Argo CD resources to your cluster" and "Scale down any Argo CD instance in your cluster" to deploy all needed manifests such as config maps.
+
+Start local services:
+
+```sh
+# Ensure you point to the correct Kubernetes cluster as shown above. For example:
+export KUBECONFIG=~/.kube/config-kind
+
+make start-local
+```
+
+This will start all Argo CD services and the UI in a Docker container and expose the following ports to your host:
+
+* The Argo CD API server on port 8080
+* The Argo CD UI server on port 4000
+* The Helm registry server on port 5000
+
+If you get firewall dialogs, for example on macOS, you can click "Deny", since no access from outside your computer is typically desired.
+
+Check that all programs have started:
+
+```text
+$ goreman run status
+*controller
+*api-server
+[...]
+```
+
+If not all critical processes run (marked with `*`), check logs to see why they terminated.
+
+In case of an error like `gpg: key generation failed: Unknown elliptic curve` (a [gnupg bug](https://dev.gnupg.org/T5444)), disable GPG verification before running `make start-local`:
+
+```sh
+export ARGOCD_GPG_ENABLED=false
+```
+
+You may get an error listening on port 5000 on macOS:
+
+```text
+docker: Error response from daemon: Ports are not available: exposing port TCP 0.0.0.0:5000 -> 0.0.0.0:0: listen tcp 0.0.0.0:5000: bind: address already in use.
+```
+
+In that case, you can disable "AirPlay Receiver" in macOS System Preferences.
+
+You can now use either the web UI by pointing your browser to `http://localhost:4000` or use the CLI against the API at `http://localhost:8080`. Be sure to use the `--insecure` and `--plaintext` options to the CLI. Webpack will take a while to bundle resources initially, so the first page load can take several seconds or minutes.
 
 As an alternative to using the above command line parameters each time you call `argocd` CLI, you can set the following environment variables:
 
@@ -59,9 +148,22 @@ export ARGOCD_SERVER=127.0.0.1:8080
 export ARGOCD_OPTS="--plaintext --insecure"
 ```
 
-### Scale up ArgoCD in your cluster
+After making a code change, ensure to rebuild and restart the respective service:
+
+```sh
+# Example for working on the repo server Go code, see other service names in `Procfile`
+goreman run restart repo-server
+```
+
+Clean up when you're done:
+
+```sh
+kind delete cluster; rm -f ~/.kube/config-kind
+```
+
+### Scale up Argo CD in your cluster
 
-Once you have finished testing your changes locally and want to bring back ArgoCD in your development cluster, simply scale the deployments up again:
+Once you have finished testing your changes locally and want to bring back Argo CD in your development cluster, simply scale the deployments up again:
 
 ```bash
 kubectl -n argocd scale statefulset/argocd-application-controller --replicas 1
@@ -71,7 +173,7 @@ kubectl -n argocd scale deployment/argocd-server --replicas 1
 kubectl -n argocd scale deployment/argocd-redis --replicas 1
 ```
 
-## Run your own ArgoCD images on your cluster
+## Run your own Argo CD images on your cluster
 
 For your final tests, it might be necessary to build your own images and run them in your development cluster.