add new pattern Replace Amazon Event Bridge Event Patterns with Lambda filter

README.md

@@ -32,6 +32,7 @@ This repo contains AWS CDK implementation for the patterns at [Serverless Land :
 | [Orchestration to Choreography](patterns/orchestration_%20to_choreography.md) | Convert the collaboration pattern from orchestration to choreography |
 | [Replace Parallel with SNS Scatter-Gather](patterns/parallel_to_sns_scatter_gather.md) | Instead of making parallel invocations from a StepFunctions `Parallel` step, send a message to SNS  |
 |[Extract Message Filter](patterns/extract-message-filter.md)|Instead of conditional statements at the consumer, eliminate unwanted messages with Amazon EventBridge.|
+| [Replace Amazon Event Bridge Event Patterns with Lambda filter](patterns/replace_event_pattern_with_lambda.md) | Replace Event Bridge Event Pattern  with Lambda filter for complex filtering logic  |
 
 
 

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implementation/replace-eventpattern-with-lambda/.gitignore

@@ -0,0 +1,8 @@
+*.js
+!jest.config.js
+*.d.ts
+node_modules
+
+# CDK asset staging directory
+.cdk.staging
+cdk.out

implementation/replace-eventpattern-with-lambda/.npmignore

@@ -0,0 +1,6 @@
+*.ts
+!*.d.ts
+
+# CDK asset staging directory
+.cdk.staging
+cdk.out

implementation/replace-eventpattern-with-lambda/README.md

@@ -0,0 +1,224 @@
+# Replace Amazon Event Bridge Event Patterns with Lambda filter
+
+This project is the CDK implementation of ['Replace Amazon Event Bridge Event Patterns with Lambda filter'](https://serverlessland.com/refactoring-serverless/replace-eventpattern-with-lambda) pattern. It shows how can you use Lambda  in CDK to filter and route messages to target service(s) to process the event instead of Amazon EventBridge's event pattern matching when complex filtering logic or data manipulation may be required before forwarding the events to the target service(s).
+
+## How it works
+
+The provided example mimics an e-commerce application where Event Bridge is used as destination of user review messages. In our example we would like to route based on product rating, number of historic purchased items.
+
+Example JSON event message:
+
+``` Json
+{
+    "source": "ecommerce.application",
+    "detail-type": "user.review",
+    "detail": {
+      "productId": "12345",
+      "rating": 4.5,
+      "reviewText": "Great product!",
+      "reviewer": {
+        "userId": "67890",
+        "email": "bob.buyer@example.com",
+        "signupDate": "2023-04-01T00:00:00Z",
+        "purchaseHistory": [
+          {
+            "orderId": "10001",
+            "orderDate": "2023-04-01T02:30:00Z",
+            "items": [{"productId": "12345", "quantity": 1}]
+          },
+          {
+            "orderId": "10002",
+            "orderDate": "2023-07-01T02:30:00Z",
+            "items": [{"productId": "12981920", "quantity": 2}]
+          },
+          {
+            "orderId": "10003",
+            "orderDate": "2023-08-01T02:30:00Z",
+            "items": [{"productId": "55667788", "quantity": 3}]
+          }
+        ]
+      }
+    }
+}
+```
+
+The provided code will deploy the following two stacks:
+
+* OriginalReplaceEventpatternWithLambdaStack
+* RefactoredReplaceEventpatternWithLambdaStack
+
+Both stack deploy two lambda functions: [Original|Refactored]EventDestinationFunction1 and [Original|Refactored]EventDestinationFunction2.
+
+OriginalReplaceEventpatternWithLambdaStack in addition deploys two Event Bridge Rules Patterns:
+
+``` typescript
+    const eventPatternFilterFunc1: events.EventPattern = {
+      source: ['ecommerce.application'],
+      detailType: ['user.review'],
+      detail: {
+        rating: [
+          {
+            numeric: ['>=', 4.5],
+          },
+        ],
+      },
+    };
+
+    const eventPatternFilterFunc2: events.EventPattern = {
+      source: ['ecommerce.application'],
+      detailType: ['user.review'],
+      detail: {
+        rating: [
+          {
+            numeric: ['<', 2],
+          },
+        ],
+      },
+    };
+```
+
+RefactoredReplaceEventpatternWithLambdaStack deploys a simple event pattern and a lambda function `EventFilterFunction` that executes complex filtering and routing.
+
+Event Pattern:
+
+``` typescript
+const eventPatternPass: events.EventPattern = {
+      source: ['ecommerce.application'],
+      detailType: ['user.review'],
+    };
+```
+
+Filter logic in the lambda function:
+
+``` Python
+def process_review_event(event):
+    rating = event['detail']['rating']
+    purchase_history = event['detail']['reviewer']['purchaseHistory']
+    total_items_purchased = sum(item['quantity'] for order in purchase_history for item in order['items'])
+
+    if rating >= 4.5 and total_items_purchased <= 10:
+        lambda_client.invoke(FunctionName=LAMBDA_DEST_FUNCTION_1, Payload=json.dumps(event))
+        logging.info(f"rating >= 4.5 and total_items_purchased({total_items_purchased}) <= 10 -> invoking {LAMBDA_DEST_FUNCTION_1}")
+    elif rating < 2 and total_items_purchased > 10:
+        lambda_client.invoke(FunctionName=LAMBDA_DEST_FUNCTION_2, Payload=json.dumps(event))
+        logging.info(f"rating < 2 and total_items_purchased({total_items_purchased}) > 10 -> invoking {LAMBDA_DEST_FUNCTION_2}")
+```
+
+## Deploy the infrastructure
+
+To build this app, navigate to `implementation/replace-eventpattern-with-lambda` folder. Then run the following:
+
+```bash
+npm install -g aws-cdk
+npm install
+npm run build
+```
+
+This will install the necessary CDK, dependencies, build your TypeScript files and CloudFormation template.
+
+Next, deploy the 2 Stacks to your AWS Account.
+
+``` bash
+cdk deploy --all
+```
+
+## Testing it out
+
+- First lets send a message to the `default` event bus executing the following command:
+
+``` bash
+aws events put-events --entries file://example_event.json
+```
+
+You should see the following:
+
+``` Json
+{
+    "FailedEntryCount": 0,
+    "Entries": [
+        {
+            "EventId": "fdb55454-114c-3642-6a55-fb960ba0dcbf"
+        }
+    ]
+}
+```
+
+## Verify
+
+``` bash
+aws logs describe-log-groups --query 'logGroups[?ends_with(logGroupName, `ScatterGatherWithSNSStack-refactorlambdaaggregator-nfXGleA7rZsh`)].logGroupName' --output text
+```
+
+Use the log group name from the previous command to get the logs of the aggregator function and filter by "quotes". Please replace your log group name in the following command.
+
+``` bash
+aws logs tail /aws/lambda/ScatterGatherWithSNSStack-refactorlambdaaggregator-nfXGleA7rZsh  --filter-pattern "quotes" 
+```
+
+The two stacks provisioned the following Lambda functions:
+
+* ```EventFilterFunction```
+* ```RefactoredEventDestinationFunction1```
+* ```RefactoredEventDestinationFunction2```
+* ```OriginalEventDestinationFunction2```
+* ```OriginalEventDestinationFunction1```
+
+Let's inspect the logs of the ```EventFilterFunction```, ```RefactoredEventDestinationFunction1``` and ```OriginalEventDestinationFunction1```.
+
+For each of the use cases we will first get the lates log stream of the and then get the log events using the aws cli.
+
+EventFilterFunction:
+
+``` Bash
+stream_name=$(aws logs describe-log-streams --log-group-name /aws/lambda/EventFilterFunction --order-by LastEventTime --descending --limit 1 | jq -r '.logStreams[0].logStreamName')
+aws logs get-log-events --log-group-name /aws/lambda/EventFilterFunction  --log-stream-name $stream_name | jq '.events | map(select(.message | contains("[INFO]")))'
+```
+
+You should see:
+
+``` Json
+[
+  {
+    "timestamp": 1691161162130,
+    "message": "[INFO]\t2023-08-04T14:59:22.129Z\tf5366ef3-2a31-4b49-8218-e1b4c4abfc7a\trating >= 4.5 and total_items_purchased(6) <= 10 -> invoking RefactoredEventDestinationFunction1\n",
+    "ingestionTime": 1691161162889
+  }
+]
+```
+
+RefactoredEventDestinationFunction1 and OriginalEventDestinationFunction1:
+
+``` Bash
+stream_name=$(aws logs describe-log-streams --log-group-name /aws/lambda/OriginalEventDestinationFunction1 --order-by LastEventTime --descending --limit 1 | jq -r '.logStreams[0].logStreamName')
+aws logs get-log-events --log-group-name /aws/lambda/OriginalEventDestinationFunction1  --log-stream-name $stream_name | jq '.events | map(select(.message | contains("[INFO]")))'
+```
+
+and
+
+``` Bash
+stream_name=$(aws logs describe-log-streams --log-group-name /aws/lambda/RefactoredEventDestinationFunction1 --order-by LastEventTime --descending --limit 1 | jq -r '.logStreams[0].logStreamName')
+aws logs get-log-events --log-group-name /aws/lambda/RefactoredEventDestinationFunction1  --log-stream-name $stream_name | jq '.events | map(select(.message | contains("[INFO]")))'
+```
+
+You should get:
+
+``` Json
+[
+  {
+    "timestamp": 1691158134746,
+    "message": "[INFO]\t2023-08-04T14:08:54.746Z\t0115f9ac-f35a-4b33-91cd-7d9aebb401ff\tHello from Rule1 handler function\n",
+    "ingestionTime": 1691158137055
+  },
+  {
+    "timestamp": 1691158134746,
+    "message": "[INFO]\t2023-08-04T14:08:54.746Z\t0115f9ac-f35a-4b33-91cd-7d9aebb401ff\tReceived Event: {\"version\": \"0\", \"id\": \"e15f7622-3c9d-1186-a3a3-736f84aeb58b\", \"detail-type\": \"user.review\", \"source\": \"ecommerce.application\", \"account\": \"446084752553\", \"time\": \"2023-08-04T14:08:53Z\", \"region\": \"us-east-1\", \"resources\": [], \"detail\": {\"productId\": \"12345\", \"rating\": 4.5, \"reviewText\": \"Great product!\", \"reviewer\": {\"userId\": \"67890\", \"email\": \"example@example.com\", \"signupDate\": \"2023-04-01T00:00:00Z\", \"purchaseHistory\": [{\"orderId\": \"10001\", \"orderDate\": \"2023-04-01T02:30:00Z\", \"items\": [{\"productId\": \"12345\", \"quantity\": 1}]}]}}}\n",
+    "ingestionTime": 1691158137055
+  }
+]
+```
+
+## Cleanup
+
+``` bash
+cdk destroy --all
+```

implementation/replace-eventpattern-with-lambda/bin/replace-eventpattern-with-lambda.ts

@@ -0,0 +1,9 @@
+#!/usr/bin/env node
+import 'source-map-support/register';
+import * as cdk from 'aws-cdk-lib';
+import { OriginalReplaceEventpatternWithLambdaStack } from '../lib/original-replace-eventpattern-with-lambda-stack';
+import { RefactoredReplaceEventpatternWithLambdaStack } from '../lib/refactored-replace-eventpattern-with-lambda-stack';
+
+const app = new cdk.App();
+new OriginalReplaceEventpatternWithLambdaStack(app, 'OriginalReplaceEventpatternWithLambdaStack', {});
+new RefactoredReplaceEventpatternWithLambdaStack(app, 'RefactoredReplaceEventpatternWithLambdaStack', {});