Taming and Testing the Cloud Environment for your Java apps with LocalStack & Testcontainers (Java Vienna 2024)

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Taming and Testing the Cloud Environment for your Java apps with LocalStack & Testcontainers 08.01.2024 Vienna

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Anca Ghenade - Developer Advocate - anca.ghenade@localstack.cloud @tinyg210

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How does one go around developing applications using AWS services?

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A Little Story About Cloud Development

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1. The Software Engineers are tasked with developing a new web application on AWS Cloud

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2. Developing on a local machine, they soon ﬁnd out that there are lots of dependencies with resources in the cloud

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3. They realize that the dev & test loop is extremely slow and tedious. Every local change needs to be packaged and uploaded to the cloud for testing.

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4. Now someone has a red build on their feature branch, but can’t efficiently test and debug their code in the CI/CD pipeline.

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5. The whole team is using Git ﬂow for development - one CI build per feature branch. There is an explosion of different environments required for development (branches x developers).

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6. The manager approaches the team and complains that AWS dev/test resources are not being cleaned up properly causing cost spikes.

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So things are kind of… complicated. 󰤆

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Additionally…

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5 minutes later…

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What is LocalStack and how can it help you? A fully functional local cloud stack that was born out of these exact concerns.

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● Enables a highly eﬃcient dev & test loop for cloud apps ● Ships as a Docker image, easy to install and start up ● Support for 90 (-ish) services (and growing): ○ compute (Lambda, ECS, EKS) ○ various databases (DynamoDB, RDS) ○ messaging (SQS, Kinesis, MSK) ○ some sophisticated/exotic APIs (Athena, Glue) ● CI integrations & advanced collaboration features ● Branching out into other areas: Chaos Engineering, IAM Security Testing, Cloud Ephemeral Environments, 3rd Party Extensions, etc

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https://github.com/localstack-samples/sample-shipment-list-demo-lambda-dynamodb-s3

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Using Spring Proﬁles…

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Scenario 1 (Production) Scenario 2 (Development)

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Scenario 1 Scenario 2

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“Your application won’t even know the difference”

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What about integration tests?

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Testing your application workﬂow

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There are several ways to provision your infrastructure for testing.

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1. You do everything yourself. (https://github.com/tinyg210/testcontainers-shipment-list-demo)

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2. You use AWS CLI scripts via init hooks. (example: https://github.com/tinyg210/stack-bytes-apigw-lambda-s3)

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3. You get inventive and run Terraform conﬁguration ﬁles from your Java tests.

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But maybe don’t. 󰤆

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4. Use LocalStack Cloud Pods (https://github.com/tinyg210/testcontainers-shipment-list-cloud-pods)

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5. Use a mix of all of the above. - export only desired services with Cloud Pods - manage other resources via SDK clients

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What about CI?

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● Automated Testing ● Continuous Deployment ● Integration Testing ● Code Quality Analysis ● Infrastructure as Code (IaC) Validation ● Containerization and Orchestration ● Feature Branch Testing ● Rollbacks and Blue/Green Deployments ● Performance Testing and Scalability ● Automated Documentation Generation

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I’ll show you some stuff

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Your local tests…

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In CI…

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Some Tips and Tricks

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Use a waiter to make sure your Lambdas are in state ACTIVE and not just created.

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Source: https://aws.amazon.com/blogs/compute/coming-soon-expansion-of-aws-lambda-states-to-all-functions/

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Use this nifty conﬁguration to scan the LocalStack logs and make sure your instance is in the right state before the tests are allowed to start: