Building reliable serverless applications - AWS Community Day Dublin October 13 2020

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Serverless “Serverless allows you to build and run applications and services without thinking about servers” Amazon Web Services (AWS)

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Serverless A distributed system has multiple components located on different machines that communicate and coordinate actions in order to appear as a single coherent system to the end-user

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Serverless – Execution models Synchronous (push) Amazon API Gateway AWS Lambda /login Asynchronous (event) AWS Lambda Amazon SNS Amazon S3 AWS Lambda AWS Lambda Stream-based AWS Lambda Amazon DynamoDB Amazon Kinesis Poll-based Amazon SQS AWS Lambda

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Reliability Reliability is the probability that a product, system, or service will perform its intended function adequately for a specified period

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Resilience A resilient system can adjust its functioning prior to, during, or following events, and thereby sustain required operations under both expected and unexpected conditions

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Decouple architectures Amazon Simple Storage Service AWS Lambda Client AWS Lambda Amazon Simple Queue Service Amazon SNS

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Decouple architectures AWS Step Functions Amazon EventBridge AWS Lambda SaaS Provider Amazon Simple Queue Service AWS Lambda Amazon DynamoDB

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Retries • Synchronous Lambdas return failures to the invoker for retry • Asynchronous Lambdas will retry up to 2 times and 6 hours • Stream-based Lambdas will store events up to 7 days for up to 10 000 retry attempts • Poll-based Lambdas will return the message to the queue up to 1 000 times for retry • SDK retries differs between runtimes and services • Beware the retry storm

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Dead letter queues • You can add dead letter queues to • SQS • SNS • Lambda • EventBridge • SQS uses SQS as DLQ • SNS uses SQS as DLQ • Lambda uses SQS or SNS as DLQ • EventBridge uses SQS as DLQ

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Lambda destinations • For asynchronous Lambda executions • Route execution record based on function result • Success • Failure • Use another Lambda function, SQS, SNS or EventBridge as destination • Record contains details about request and response in JSON

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Fallbacks “Such attempts at a completely different mechanism to try to achieve the same result are called fallback behavior, and are an anti-pattern to be avoided” Reliability Pillar AWS Well-Architected Framework

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Chaos engineering What if my function takes an extra 300 ms for each invocation? What if my function returns an error code? What if I can’t get data from DynamoDB?

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building – Chaos engineering “Chaos engineering should be done regularly, and be part of your CI/CD cycle” Reliability Pillar AWS Well-Architected Framework

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Summary Resilience isn’t something you have, it’s something you do Decouple architectures Let AWS handle errors and retries Use the circuit breaker pattern to avoid retry storms Use dead letter queues to capture events that fail to process Use Lambda destinations for function failures Fallbacks are great – when used, tested and verified often Chaos engineering helps us find weaknesses and fix them

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© 2020, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Do you want more? Patterns and practices for building resilient Serverless applications (Yan Cui) https://www.slideshare.net/theburningmonk/patterns-and-practices-for-building-resilient-serverless-applications Serverless Microservice Patterns for AWS (Jeremy Daly) https://www.jeremydaly.com/serverless-microservice-patterns-for-aws/ The Amazon Builders' Library https://aws.amazon.com/builders-library/ Timeouts, retries and backoff with jitter (Yan Cui) https://lumigo.io/blog/amazon-builders-library-in-focus-1-timeouts-retries-and-backoff-with-jitter/ Serverless Chaos Demo app https://demo.serverlesschaos.com Serverless Chaos Demo Circuit Breaker app https://circuitbreaker.serverlesschaos.com

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