Example Kubernetes pod for the multi-container sidecar design pattern

pod.yaml

# Example YAML configuration for the sidecar pattern.

# It defines a main application container which writes
# the current date to a log file every five seconds.

# The sidecar container is nginx serving that log file.
# (In practice, your sidecar is likely to be a log collection
# container that uploads to external storage.)

# To run:
#   kubectl apply -f pod.yaml

# Once the pod is running:
#   
#   (Connect to the sidecar pod)
#   kubectl exec pod-with-sidecar -c sidecar-container -it bash
#   
#   (Install curl on the sidecar)
#   apt-get update && apt-get install curl
#   
#   (Access the log file via the sidecar)
#   curl 'http://localhost:80/app.txt'

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-sidecar
spec:
  # Create a volume called 'shared-logs' that the
  # app and sidecar share.
  volumes:
  - name: shared-logs 
    emptyDir: {}

  # In the sidecar pattern, there is a main application
  # container and a sidecar container.
  containers:

  # Main application container
  - name: app-container
    # Simple application: write the current date
    # to the log file every five seconds
    image: alpine # alpine is a simple Linux OS image
    command: ["/bin/sh"]
    args: ["-c", "while true; do date >> /var/log/app.txt; sleep 5;done"]

    # Mount the pod's shared log file into the app 
    # container. The app writes logs here.
    volumeMounts:
    - name: shared-logs
      mountPath: /var/log

  # Sidecar container
  - name: sidecar-container
    # Simple sidecar: display log files using nginx.
    # In reality, this sidecar would be a custom image
    # that uploads logs to a third-party or storage service.
    image: nginx:1.7.9
    ports:
      - containerPort: 80

    # Mount the pod's shared log file into the sidecar
    # container. In this case, nginx will serve the files
    # in this directory.
    volumeMounts:
    - name: shared-logs
      mountPath: /usr/share/nginx/html # nginx-specific mount path

Good example about multi-container use case.

I'm getting error
error: a container name must be specified for pod pod-with-sidecar, choose one of: [app-container sidecar-container]

I'm getting error
error: a container name must be specified for pod pod-with-sidecar, choose one of: [app-container sidecar-container]

Seems you check logs on pod, to do that you need to append containers name (as per message above or append switch such as --all-containers

to send any command to a container inside a pod that is not default (there's more than 1) use -c "containerName". Example:
kubectl exec -it pod-with-sidecar -c sidecar-container -- ls -la /usr/share/nginx/html

Hello,
Now i am trying to use Pod user Manage Identity instead of service principle, Now I am able to update pod identity on my cluster and but now while trying to create ResoureGroup I am getting following error

      message: "DefaultAzureCredential: failed to acquire a token.\nAttempted credentials:\n\tEnvironmentCredential:
        incomplete environment variable configuration. Only AZURE_TENANT_ID and AZURE_CLIENT_ID
        are set\n\tWorkloadIdentityCredential: no token file specified. Check pod
        configuration or set TokenFilePath in the options\n\tManagedIdentityCredential:
        managed identity timed out\n\tAzureCLICredential: fork/exec /bin/sh: no such
        file or directory"
      observedGeneration: 1
      reason: UnknownError 

Below are the steps I have performed it on our Private AKS cluster

Step1:

az aks update \
    --resource-group dev \
    --name dev-cluster  \
    --enable-managed-identity \
    --assign-identity /subscriptions/aaaaaaaaaa/resourceGroups/dev/providers/Microsoft.ManagedIdentity/userAssignedIdentities/dev-azureoperator

az aks update --enable-pod-identity --name dev-magenta-mlops-cluster --resource-group dev-magenta --enable-pod-identity-with-kubenet

export POD_IDENTITY_NAMESPACE=azureserviceoperator-system
export IDENTITY_RESOURCE_ID="/subscriptions/aaaaaaaaaa/resourceGroups/dev/providers/Microsoft.ManagedIdentity/userAssignedIdentities/dev-azureoperator"
export POD_IDENTITY_NAME=az-pod-identity
az aks pod-identity add --resource-group dev --cluster-name dev-cluster --namespace ${POD_IDENTITY_NAMESPACE}  --name ${POD_IDENTITY_NAME} --identity-resource-id ${IDENTITY_RESOURCE_ID}

Step2: I have deployed Azure Operator using v2 helm charts

helm upgrade --install azure-service-operator . \
     --create-namespace \
     --namespace=azureserviceoperator-system \
     --set azureSubscriptionID=aaaaaaa \
     --set azureTenantID=aaaaaa \
     --set azureClientID=<Manager Identiy Clientid> \
     --set crdPattern='resources.azure.com/*;storage.azure.com/*;authorization.azure.com/*;managedidentity.azure.com/*'

Step3: Here I was getting above error
Now I am trying to create Resources on Azure

apiVersion:  resources.azure.com/v1beta20200601
kind: ResourceGroup
metadata:
  name: dev-mlflow-rg
  namespace: azureserviceoperator-system
spec:
  location: Westeurope

kubectl create resource.yaml