Add tutorial to DynamoDB registry docs

The existing docs described how to configure the DynamoDB registry, but
didn't have a tutorial for someone to walk through.

Signed-off-by: Michael Shen <mishen@umich.edu>
Co-authored-by: Michel Loiseleur <97035654+mloiseleur@users.noreply.github.com>

docs/registry/dynamodb.md

@@ -1,19 +1,11 @@
 # The DynamoDB registry
 
-The DynamoDB registry stores DNS record metadata in an AWS DynamoDB table.
+As opposed to the default TXT registry, the DynamoDB registry stores DNS record metadata in an AWS DynamoDB table instead of in TXT records in a hosted zone.
-
+This following tutorial extends [Setting up ExternalDNS for Services on AWS](../tutorials/aws.md) to use the DynamoDB registry instead.
-## The DynamoDB Table
-
-By default, the DynamoDB registry stores data in the table named `external-dns`.
-A different table may be specified using the `--dynamodb-table` flag.
-A different region may be specified using the `--dynamodb-region` flag.
-
-The table must have a partition (hash) key named `k` and string type.
-The table must not have a sort (range) key.
 
 ## IAM permissions
 
-The ExternalDNS Role must be granted the following permissions:
+The ExternalDNS [IAM Policy](../tutorials/aws.md#iam-policy) must additionally be granted the following permissions:
 
 ```json
     {
@@ -33,10 +25,138 @@ The ExternalDNS Role must be granted the following permissions:
 
 The region and account ID may be specified explicitly specified instead of using wildcards.
 
+## Create a DynamoDB Table
+
+By default, the DynamoDB registry stores data in the table named `external-dns` and it needs to exist before configuring ExternalDNS to use the DynamoDB registry.
+If the DynamoDB table has a different name, it may be specified using the `--dynamodb-table` flag.
+If the DynamoDB table is in a different region, it may be specified using the `--dynamodb-region` flag.
+
+The following command creates a DynamoDB table with the name: `external-dns`:
+
+> The table must have a partition (HASH) key named `k` of type string (`S`) and the table must NOT have a sort (RANGE) key.
+
+```bash
+aws dynamodb create-table \
+  --table-name external-dns \
+  --attribute-definitions \
+    AttributeName=k,AttributeType=S \
+  --key-schema \
+    AttributeName=k,KeyType=HASH \
+  --provisioned-throughput \
+    ReadCapacityUnits=5,WriteCapacityUnits=5 \
+  --table-class STANDARD
+```
+
+## Set up a hosted zone
+
+Follow [Set up a hosted zone](../tutorials/aws.md#set-up-a-hosted-zone)
+
+## Modify ExternalDNS deployment
+
+The ExternalDNS deployment from [Deploy ExternalDNS](../tutorials/aws.md#deploy-externaldns) needs the following modifications:
+
+* `--registry=txt` should be changed to `--registry=dynamodb`
+* Add `--dynamodb-table=external-dns` to specify the name of the DynamoDB table, its value defaults to `external-dns`
+* Add `--dynamodb-region=us-east-1` to specify the region of the DynamoDB table
+
+For example:
+
+```yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: external-dns
+  labels:
+    app.kubernetes.io/name: external-dns
+spec:
+  strategy:
+    type: Recreate
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: external-dns
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: external-dns
+    spec:
+      containers:
+        - name: external-dns
+          image: registry.k8s.io/external-dns/external-dns:v0.14.1
+          args:
+            - --source=service
+            - --source=ingress
+            - --domain-filter=example.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
+            - --provider=aws
+            - --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
+            - --aws-zone-type=public # only look at public hosted zones (valid values are public, private or no value for both)
+            - --registry=dynamodb # previously, --registry=txt
+            - --dynamodb-table=external-dns # defaults to external-dns
+            - --dynamodb-region=us-east-1 # set to the region the DynamoDB table in
+            - --txt-owner-id=my-hostedzone-identifier
+          env:
+            - name: AWS_DEFAULT_REGION
+              value: us-east-1 # change to region where EKS is installed
+      # # Uncomment below if using static credentials
+      #       - name: AWS_SHARED_CREDENTIALS_FILE
+      #        value: /.aws/credentials
+      #     volumeMounts:
+      #       - name: aws-credentials
+      #         mountPath: /.aws
+      #         readOnly: true
+      # volumes:
+      #   - name: aws-credentials
+      #     secret:
+      #       secretName: external-dns
+```
+
+## Validate ExternalDNS works
+
+Create either a [Service](../tutorials/aws.md#verify-externaldns-works-service-example) or an [Ingress](../tutorials/aws.md#verify-externaldns-works-ingress-example) and 
+
+After roughly two minutes, check that the corresponding entry was created in the DynamoDB table:
+
+```bash
+aws dynamodb scan --table-name external-dns
+```
+
+This will show something like:
+```
+{
+    "Items": [
+        {
+            "k": {
+                "S": "nginx.example.com#A#"
+            },
+            "o": {
+                "S": "my-identifier"
+            },
+            "l": {
+                "M": {
+                    "resource": {
+                        "S": "service/default/nginx"
+                    }
+                }
+            }
+        }
+    ],
+    "Count": 1,
+    "ScannedCount": 1,
+    "ConsumedCapacity": null
+}
+```
+
+## Clean up
+
+In addition to the clean up steps in [Setting up ExternalDNS for Services on AWS](../tutorials/aws.md#clean-up), delete the DynamoDB table that was used as a registry.
+
+```bash
+aws dynamodb delete-table \
+  --table-name external-dns
+```
+
 ## Caching
 
-The DynamoDB registry can optionally cache DNS records read from the provider. This can mitigate
+The DynamoDB registry can optionally cache DNS records read from the provider. This can mitigate rate limits imposed by the provider.
-rate limits imposed by the provider.
 
 Caching is enabled by specifying a cache duration with the `--txt-cache-interval` flag.
 

docs/tutorials/aws.md

@@ -856,6 +856,10 @@ env:
       key: {{ YOUR_SECRET_KEY }}
 ```
 
+## DynamoDB Registry
+
+The DynamoDB Registry can be used to store dns records metadata. See the [DynamoDB Registry Tutorial](../registry/dynamodb.md) for more information.
+
 ## Clean up
 
 Make sure to delete all Service objects before terminating the cluster so all load balancers get cleaned up correctly.