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Package software.amazon.awscdk.services.lambda.destinations

Amazon Lambda Destinations Library

See: Description

Package software.amazon.awscdk.services.lambda.destinations Description

Amazon Lambda Destinations Library

---

cdk-constructs: Stable


This library provides constructs for adding destinations to a Lambda function. Destinations can be added by specifying the onFailure or onSuccess props when creating a function or alias.

Destinations

The following destinations are supported

Example with a SNS topic for successful invocations:

 // Example automatically generated without compilation. See https://github.com/aws/jsii/issues/826
 import software.amazon.awscdk.services.lambda.*;
 import software.amazon.awscdk.services.lambda.destinations.*;
 import software.amazon.awscdk.services.sns.*;
 
 Topic myTopic = new Topic(this, "Topic");
 
 Function myFn = Function.Builder.create(this, "Fn")
         // other props
         .onSuccess(new SnsDestination(myTopic))
         .build();
 

See also Configuring Destinations for Asynchronous Invocation.

Invocation record

When a lambda function is configured with a destination, an invocation record is created by the Lambda service when the lambda function completes. The invocation record contains the details of the function, its context, and the request and response payloads.

The following example shows the format of the invocation record for a successful invocation:

 {
        "version": "1.0",
        "timestamp": "2019-11-24T23:08:25.651Z",
        "requestContext": {
                "requestId": "c2a6f2ae-7dbb-4d22-8782-d0485c9877e2",
                "functionArn": "arn:aws:lambda:sa-east-1:123456789123:function:event-destinations:$LATEST",
                "condition": "Success",
                "approximateInvokeCount": 1
        },
        "requestPayload": {
                "Success": true
        },
        "responseContext": {
                "statusCode": 200,
                "executedVersion": "$LATEST"
        },
        "responsePayload": "<data returned by the function here>"
 }
 

In case of failure, the record contains the reason and error object:

 {
     "version": "1.0",
     "timestamp": "2019-11-24T21:52:47.333Z",
     "requestContext": {
         "requestId": "8ea123e4-1db7-4aca-ad10-d9ca1234c1fd",
         "functionArn": "arn:aws:lambda:sa-east-1:123456678912:function:event-destinations:$LATEST",
         "condition": "RetriesExhausted",
         "approximateInvokeCount": 3
     },
     "requestPayload": {
         "Success": false
     },
     "responseContext": {
         "statusCode": 200,
         "executedVersion": "$LATEST",
         "functionError": "Handled"
     },
     "responsePayload": {
         "errorMessage": "Failure from event, Success = false, I am failing!",
         "errorType": "Error",
         "stackTrace": [ "exports.handler (/var/task/index.js:18:18)" ]
     }
 }
 

Destination-specific JSON format

Auto-extract response payload with lambda destination

The responseOnly option of LambdaDestination allows to auto-extract the response payload from the invocation record:

 // Example automatically generated without compilation. See https://github.com/aws/jsii/issues/826
 import software.amazon.awscdk.services.lambda.*;
 import software.amazon.awscdk.services.lambda.destinations.*;
 
 Function destinationFn = Function.Builder.create(this, "Destination").build();
 
 Function sourceFn = Function.Builder.create(this, "Source")
         // other props
         .onSuccess(LambdaDestination.Builder.create(destinationFn)
                 .responseOnly(true)
                 .build())
         .build();
 

In the above example, destinationFn will be invoked with the payload returned by sourceFn (responsePayload in the invocation record, not the full record).

When used with onFailure, the destination function is invoked with the error object returned by the source function.

Using the responseOnly option allows to easily chain asynchronous Lambda functions without having to deal with data extraction in the runtime code.

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