Using Amazon DynamoDB

The first step in this process is to re-configure the carts service to use a DynamoDB table that has already been created for us. The application loads most of its confirmation from a ConfigMap, lets take look at it:

~$kubectl -n carts get -o yaml cm carts

apiVersion: v1

data:

  AWS_ACCESS_KEY_ID: key

  AWS_SECRET_ACCESS_KEY: secret

  CARTS_DYNAMODB_CREATETABLE: true

  CARTS_DYNAMODB_ENDPOINT: http://carts-dynamodb:8000

  CARTS_DYNAMODB_TABLENAME: Items

kind: ConfigMap

metadata:

  name: carts

  namespace: carts

Also, check the current status of the application the using the browser. A LoadBalancer type service named ui-nlb is provisioned in the ui namespace from which the application's UI can be accessed.

~$kubectl -n ui get service ui-nlb -o jsonpath='{.status.loadBalancer.ingress[*].hostname}{"\n"}'

k8s-ui-uinlb-647e781087-6717c5049aa96bd9.elb.us-west-2.amazonaws.com

Use the generated URL from the command above to open the UI in your browser. It should open the the Retail Store like shown below.

Now, the following kustomization overwrites the ConfigMap, removing the DynamoDB endpoint configuration which tells the SDK to default to the real DynamoDB service instead of our test Pod. We've also provided it with the name of the DynamoDB table thats been created already for us which is being pulled from the environment variable CARTS_DYNAMODB_TABLENAME.

Kustomize Patch

~/environment/eks-workshop/modules/security/eks-pod-identity/dynamo/kustomization.yaml

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../../../base-application/carts
configMapGenerator:
  - name: carts
    namespace: carts
    env: config.properties
    behavior: replace
    options:
      disableNameSuffixHash: true

ConfigMap/carts

apiVersion: v1
data:
  CARTS_DYNAMODB_TABLENAME: ${CARTS_DYNAMODB_TABLENAME}
kind: ConfigMap
metadata:
  name: carts
  namespace: carts

Diff

 apiVersion: v1
 data:
-  AWS_ACCESS_KEY_ID: key
-  AWS_SECRET_ACCESS_KEY: secret
-  CARTS_DYNAMODB_CREATETABLE: "true"
-  CARTS_DYNAMODB_ENDPOINT: http://carts-dynamodb:8000
-  CARTS_DYNAMODB_TABLENAME: Items
+  CARTS_DYNAMODB_TABLENAME: ${CARTS_DYNAMODB_TABLENAME}
 kind: ConfigMap
 metadata:
   name: carts
   namespace: carts

Let's check the value of CARTS_DYNAMODB_TABLENAME then run Kustomize to use the real DynamoDB service:

~$echo $CARTS_DYNAMODB_TABLENAME

eks-workshop-carts

~$kubectl kustomize ~/environment/eks-workshop/modules/security/eks-pod-identity/dynamo \

| envsubst | kubectl apply -f-

This will overwrite our ConfigMap with new values:

~$kubectl -n carts get cm carts -o yaml

apiVersion: v1

data:

  CARTS_DYNAMODB_TABLENAME: eks-workshop-carts

kind: ConfigMap

metadata:

  labels:

    app: carts

  name: carts

  namespace: carts

We'll need to recycle all the Pods of the carts application to pick up our new ConfigMap contents.

~$kubectl -n carts rollout restart deployment/carts

deployment.apps/carts restarted

~$kubectl -n carts rollout status deployment/carts

So now our application should be using DynamoDB right? Try to load it up in the browser using the URL from the previous command, and navigate to the shopping cart.

~$kubectl -n ui get service ui-nlb -o jsonpath='{.status.loadBalancer.ingress[*].hostname}{"\n"}'

k8s-ui-uinlb-647e781087-6717c5049aa96bd9.elb.us-west-2.amazonaws.com

The shopping cart page is not accessible! What's gone wrong?