Add EventBridge handler example

Author: jeastham1993

docs/patterns/messaging-patterns/eventbridge-event-handler.md

@@ -0,0 +1,156 @@
+---
+sidebar_position: 2
+title: EventBridge Event Handler
+description: Lambda function for handling an event from Amazon EventBridge
+keywords: [rust,lambda,eventbridge,messaging,putevent]
+---
+
+As mentioned in several of the other messaging quick starts, the publisher/subscriber (pub/sub) pattern is extremely common in a serverless architecture. Severless encourages micro and someties even nano-sized components that are assembled together by way of contracts as opposed to building everything into a single binary.
+
+AWS' EventBridge is a service that describes itself like this:
+
+> Amazon EventBridge Event Bus is a serverless event bus that helps you receive, filter, transform, route, and deliver events. - AWS
+
+It provides a Default Bus or you are able to add Custom Event Buses to fit your need.  This article will look to showcase how to create a Lambda function that handles an event from an EventBridge custom bus. It also takes the publishing component from the article on [Event Bridge Put Events](./eventbridge-putevent.md) to give a cohesive pub/sub experience.
+
+## How It Works
+
+The sample in this tutorial builds upon a Lambda that listens on a Function URL and then generates an EventBridge PutEvent with a custom domain model. A Rule is defined by the subscriber on the custom event bus that sends any matching messages to a Lambda function. The subscriber Lambda function will deserialize and process the message.
+
+The EventBridge -> Lambda integration is an example of an [async invoke](../../fundamentals/invocation-modes.md#asynchronous-invokes). Internally inside the Lambda service the events are queued up onto an SQS queue managed by Lambda, and your function is invoked from here.
+
+An important note, the sample application deploys the publisher, subscriber and event bus using the same infrastructure as code template. This is for ease of demonstration. Typically the 3 components would be deployed as 3 independent stacks.
+
+## Project Structure
+
+A Lambda and EventBridge Event handler template is found under the [./templates](https://github.com/serverlessdevelopers/serverless-rust/tree/main/templates/patterns/messaging-patterns/eventbridge-handler) directory in the GitHub repo. You can use template to get started building with EventBridge and Lambda.
+
+The template is simple, and is based upon the following structure.
+
+```bash
+lambdas
+  - event-handler
+  - publisher
+  - shared
+```
+
+## Lambda Code
+
+### Main 
+
+<CH.Section>
+
+When handling messages from EventBridge with Lambda your Lambda code will look much like the other services covered as part of the [messaging patterns](../messaging-patterns/). The main function sets up the logging framework, and then starts the Lambda runtime. Passing in the [function to use as the handler](focus://9).
+
+```rust
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+    tracing_subscriber::fmt()
+        .with_max_level(tracing::Level::INFO)
+        .with_target(false)
+        .without_time()
+        .init();
+
+    run(service_fn(function_handler)).await
+}
+```
+
+</CH.Section>
+
+### Handler Code
+
+<CH.Section>
+The handler code in this sample is deserializing the `detail` of the event that comes from EventBridge and using a handler from your custom business logic to actually process the message.
+
+The [`LambdaEvent` that comes into your handler function is of type `CloudWatchEvent`](focus://1[26:63]). Before EventBridge became it's own service, it was called CloudWatch events. Hence the name of the struct being `CloudWatchEvent`. 
+
+For re-usability, a custom [`InternalMessage`](focus://2) struct is used as a wrapper around the `CloudWatchEvent` type that comes from the [Lambda events Crate](https://docs.rs/aws_lambda_events/latest/aws_lambda_events/). This allows the [`try_into()`](focus://3) function to be used to handle the conversion from the custom CloudWatchEvent type into the `Payload` type used by the application.
+
+Note that if the [`try_into()` call fails](focus://14:16) or the [`handle()` function call fails](focus://11) the handler returns an error. This will return an error back to the Lambda runtime. 
+
+```rust
+async fn function_handler(event: LambdaEvent<CloudWatchEvent>) -> Result<(), Error> {
+    let payload: Result<Payload, MessageParseError> = InternalMessage(event.payload)
+        .try_into();
+
+    match payload {
+        Ok(payload) => {
+            let _handle_res = PayloadHandler::handle(&payload).await;
+
+            match _handle_res {
+                Ok(_) => Ok(()),
+                Err(e) => Err(e.into())
+            }
+        }
+        Err(err) => {
+            Err(err.into())
+        }
+    }
+}
+```
+</CH.Section>
+
+<CH.Section>
+
+By default, EventBridge retries sending the event for 24 hours and up to 185 times with an exponential back off and jitter, or randomized delay. You can [control this retry behavior](focus://12:16), and the routing to a dead letter queue, using your Lambda event source configuration. This example uses AWS SAM to automatically create an [SQS queue](focus://14:16) for failures, and route any failed messages to the [DLQ after only one retry](focus://13).
+
+```yaml
+  EventHandlerFunction:
+    Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
+    Metadata:
+      BuildMethod: rust-cargolambda
+      BuildProperties:
+        Binary: event-bridge-handler
+    Properties:
+      FunctionName: serverless-rust-EventHandler
+      CodeUri: .
+      Handler: bootstrap
+      Runtime: provided.al2023
+      EventInvokeConfig:
+        MaximumRetryAttempts: 1
+        DestinationConfig:
+          OnFailure:
+            Type: SQS
+      Architectures:
+        - arm64
+      Events:
+        Trigger:
+          Type: CloudWatchEvent
+          Properties:
+            EventBusName: !GetAtt RustDemoEventBus.Name
+            Pattern:
+              source:
+                - RustDemo
+```
+
+</CH.Section>
+
+## Deploy
+
+You can deploy this example directly to your own AWS account using the [provided template](https://github.com/serverlessdevelopers/serverless-rust/tree/main/templates/patterns/messaging-patterns/eventbridge-handler). Simply clone the repo, and then run the below CLI commands from the repo root.
+
+```
+cd templates/patterns/messaging-patterns/eventbridge-handler/
+sam build --beta-features
+sam deploy
+```
+
+Once deployed, you can send a POST request to the Lambda function URL endpoint with the below body:
+
+```json
+{
+    "name": "James",
+    "message": "Hello YouTube"
+}
+```
+
+After running the POST request and getting back a 200 response, you can use the `sam logs` CLI command to retrieve the logs for your EventBridge handler function.
+
+```
+sam logs --profile sandbox --stack-name event-bridge-rust
+```
+
+## Congrats
+
+And that's all there is to it.  This was a simple example but highlights how you can use Rust, Lambda and EventBridge to build high performance event driven systems.
+

docs/patterns/messaging-patterns/sam-lambda-kinesis-message-processor.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 2
+sidebar_position: 5
 title: Kinesis Message Processor
 description: Lambda function for processing messages from a Kinesis stream
 keywords: [rust,lambda,kinesis,messaging,streaming data]

docs/patterns/messaging-patterns/sam-lambda-sns-topic-processor.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 3
+sidebar_position: 4
 title: SNS Message Processor
 description: Lambda function for processing messages from an SNS topic
 keywords: [rust,lambda,sns,messaging,publish subscribe channels]

docs/patterns/messaging-patterns/sam-lambda-sqs-message-processor.mdx

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 4
+sidebar_position: 3
 title: SQS Message Processor
 description: Lambda function for processing messages from an SQS queue
 keywords: [rust,lambda,sqs,messaging,point to point channels]