Lambda

• To increase performance keep connect or close statements outside of the handler, Place the connection in the global space or have login in program to check db connectivity before making connections

• Lambda needs permission to be granted to write to CloudWatch logs , if no permission then nothing will be written to CloudWatch logs

• If no logs are being written to CloudWatch logs lambda doesn’t not have permission to write logs

  • Most important ones are below 2

    • AWSLambdaBasicExecutionRole : write logs to CloudWatch

    • AWSXRayDaemonWriteAccess: upload trace data to X-Ray

  • Others include

    • AWSLambdaSQSQueueExecutionRole: read a message from SQS.

    • AWSLambdaVPCAccessExecutionRole: to manage elastic network interfaces to connect your function to VPC

    • CloudWatchLambdaInsightsExecutionRolePolicy: To write runtime metrics to CloudWatch Lambda Insights.

    • AWSLambdaDynamoDBExecutionRole: Read records from DynamoDB stream.

    • AWSLambdaKinesisExecutionRole: events from Kinesis data stream or consumer.

    • AWSLambdaMQExecutionRole: read records from an Amazon MQ broker.

    • AWSLambdaMSKExecutionRole: Permission to read records from Amazon MSK cluster.

• You increase memory (128MB to 10GB in 1MB incr) to increase CPU, ( this increases cost)

• Aliases

  • Pointer to a specific Lambda function version

• Layers

  • A layer is just a ZIP archive that contains libraries, a custom runtime, or other dependencies

  • used to pull in additional code and content in the form of layers

• Environment variables

  • Enable you to dynamically pass settings to your function code and libraries, without making changes to your code

  • Ex: Lambda function which will run in various environments such as DEV, TEST, UAT, and PROD , and call different API for different environments

• Synchronous invocation

  • Wait for the function to process the event and return a response (StatusCode: 200)

  • Use cases : API Gateway, CloudFront

• Asynchronous invocation

  • Lambda queues the event for processing and returns a response immediately and without additional information (StatusCode: 202)

  • use the invoke command with --invocation-type parameter to Event

  • Use cases: S3 , SNS

• HTTP Status Code: 429 ( or 502): TooManyRequestsException ,

  • Exceeded allowed concurrency , throttling occurs with 429

  • The request throughput limit was exceeded 🡺 for Synchronous invocations.

  • Asynchronous invocation 🡺 retry, then to DLQ (Dead letter Queue)

• HTTP Status Code 504 (5XX)

  • INTEGRATION_FAILURE, INTEGRATION_TIMEOUT

  • INTEGRATION_TIMEOUT range is 50 milliseconds to 29 seconds

• InvalidParameterValueException

  • one of the parameters in the request is invalid, ex: if you provided an IAM role in the CreateFunction API which AWS Lambda is unable to assume IAM role

  • Unzipped package is bigger than allotted size

• CodeStorageExceededException

  • exceeded your maximum total code size per account

• ResourceConflictException

  • resource already exists

• ServiceException

  • AWS Lambda service encountered an internal error