feat: Enable local docker ip in for communication with outside k3d (#…

…11350)

Signed-off-by: Matthias Dietz <m.dietz@ewerk.com>
Co-authored-by: Matthias Dietz <m.dietz@ewerk.com>

.devcontainer/devcontainer.json

@@ -15,6 +15,7 @@
   "hostRequirements": {
     "cpus": 4
   },
+  "runArgs": ["--add-host=host.docker.internal:host-gateway"],
   "onCreateCommand": ".devcontainer/pre-build.sh",
   "workspaceMount": "source=${localWorkspaceFolder},target=/home/vscode/go/src/github.com/argoproj/argo-workflows,type=bind",
   "workspaceFolder": "/home/vscode/go/src/github.com/argoproj/argo-workflows",

.devcontainer/pre-build.sh

@@ -14,7 +14,7 @@ k3d cluster get k3s-default || k3d cluster create --wait
 k3d kubeconfig merge --kubeconfig-merge-default
 
 # install kubectl
-curl -LO https://dl.k8s.io/release/v1.26.0/bin/linux/amd64/kubectl
+curl -LO https://dl.k8s.io/release/v1.26.0/bin/linux/$(go env GOARCH)/kubectl
 chmod +x ./kubectl
 sudo mv ./kubectl /usr/local/bin/kubectl
 kubectl cluster-info
@@ -31,3 +31,6 @@ sudo chown -R vscode:vscode /home/vscode/go
 
 # download dependencies and do first-pass compile
 CI=1 kit pre-up
+
+# Patch CoreDNS to have host.docker.internal inside the cluster available
+kubectl get cm coredns -n kube-system -o yaml | sed "s/  NodeHosts: |/  NodeHosts: |\n    `grep host.docker.internal /etc/hosts`/" | kubectl apply -f -

docs/running-locally.md

@@ -12,7 +12,7 @@ generation does not work.
 
 ## Development Container
 
-A development container is a running Docker container with a well-defined tool/runtime stack and its prerequisites. It should be able to do everything you need to do to develop argo workflows using the development container without installing tools on your local machine. It takes quite a long time to build the container. It will run k3d inside the container so you'll have a cluster to use to test against.
+A development container is a running Docker container with a well-defined tool/runtime stack and its prerequisites. It should be able to do everything you need to do to develop argo workflows using the development container without installing tools on your local machine. It takes quite a long time to build the container. It will run k3d inside the container so you'll have a cluster to use to test against. To communicate with services running either in other development containers or directly on the local developer machine (e.g., a database) the following URL can be used in the workflow spec: `host.docker.internal:<PORT>`. This facilitates the implementation of workflows, which need to connect to a database or an API server.
 
 You can use the development container in a few different ways: