Skip to content

Instantly share code, notes, and snippets.

Last active June 23, 2023 13:01
  • Star 48 You must be signed in to star a gist
  • Fork 3 You must be signed in to fork a gist
Star You must be signed in to star a gist
Save jeshan/52cb021fd20d871c56ad5ce6d2654d7b to your computer and use it in GitHub Desktop.
AWS Lambda: Determine Event Source from event object. Note that this is an approximation as anybody can send a payload that resembles the real thing.
function getLambdaEventSource(event) {
if (event.Records && event.Records[0].cf) return 'isCloudfront';
if (event.configRuleId && event.configRuleName && event.configRuleArn) return 'isAwsConfig';
if (event.Records && (event.Records[0].eventSource === 'aws:codecommit')) return 'isCodeCommit';
if (event.authorizationToken === "incoming-client-token") return 'isApiGatewayAuthorizer';
if (event.StackId && event.RequestType && event.ResourceType) return 'isCloudFormation';
if (event.Records && (event.Records[0].eventSource === 'aws:ses')) return 'isSes';
if (event.pathParameters && event.pathParameters.proxy) return 'isApiGatewayAwsProxy';
if (event.source === '') return 'isScheduledEvent';
if (event.awslogs && return 'isCloudWatchLogs';
if (event.Records && (event.Records[0].EventSource === 'aws:sns')) return 'isSns';
if (event.Records && (event.Records[0].eventSource === 'aws:dynamodb')) return 'isDynamoDb';
if (event.records && event.records[0].approximateArrivalTimestamp) return 'isKinesisFirehose';
if (event.records && event.deliveryStreamArn && event.deliveryStreamArn.startsWith('arn:aws:kinesis:')) return 'isKinesisFirehose';
if (event.eventType === 'SyncTrigger' && event.identityId && event.identityPoolId) return 'isCognitoSyncTrigger';
if (event.Records && event.Records[0].eventSource === 'aws:kinesis') return 'isKinesis';
if (event.Records && event.Records[0].eventSource === 'aws:s3') return 'isS3';
if (event.operation && event.message) return 'isMobileBackend';
if (event.Records && (event.Records[0].eventSource === 'aws:sqs')) return 'isSqs';
Copy link

For Python: You can check this out This is just based on your gist. Thank you.

Copy link

Would you kindly add a if statement for a lambda being triggered by application load balancer?

Copy link

paulo-iona commented Feb 2, 2021

For API Gateway HTTP:

if (event.requestContext && event.requestContext.resourceId) return 'isApiGatewayHttp';

Copy link

jeremy-brooks commented Jun 14, 2022

This is probably not the best idea as it relies on AWS implementation details which may change.

Copy link

Interesting and useful. I have struggled with the best approach to knowing my invoker. Although this may not persist well over time it is better than putting a caller flag in the payload. The only other option I see is multiple similar functions, which leads to logic sprawl but avoids the conditional overhead.

Copy link

For SQS add this

elif 'Records' in event and len(event['Records']) > 0 and 'eventSource' in event['Records'][0] and event['Records'][0]['eventSource'] == 'aws:sqs':
return 'sqs'

Copy link

if (event.requestContext.elb.targetGroupArn) return 'is ALBEvent'

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment