gap-lambda-upload

This project contains source code and supporting files for the GAP upload lambda function.

Directories

• upload_function - Code for the application's Lambda function and Project Dockerfile.
• events - Invocation events that you can use to invoke the function.
• tests - Unit tests for the application code.
• template.yaml - A template that defines the application's AWS resources.

Overview

The lambda is part of our virus scanning support for uploaded files. It is triggered by an entry in the SNS created by Trend Micro virus scanning - events being created after a scan has been performed.

flowchart TD
  UploadS3["Upload location
  [S3]"]

  GoodS3["Safe Attachments
  [S3]"]

  BadS3["Quarantined Attachments
  [S3]"]

  TrendMicro["Trend Micro Virus Scanner
  [Software Service]
  Scans S3 for new file uploads"]
  
  ScannedQueue["Event Queue
  [Queue]
  Records results of virus scanning"]
  
  MoverLambda["Trent Micro Mover
  [Lambda]
  Moves scanned file"]

  ScanResult{Has a virus\nbeen identified?}
  
  UploadLambda["gap_lambda_upload
  [Lambda]
  Processes scanning result"]
  
  AttachmentService["Attachment Service
  [Software Service]
  Stores result details"]

  GapDatabase[(GAP\nDatabase)]

  TrendMicro-- "reads files" --> UploadS3
  TrendMicro-- "creates events" --> ScannedQueue

  ScannedQueue-- "processes events" --> MoverLambda
  UploadS3-- "moves file" --> MoverLambda
  MoverLambda--> ScanResult
  ScanResult--> |Yes| BadS3
  ScanResult--> |No| GoodS3

  ScannedQueue-- "processes events" --> UploadLambda
  UploadLambda-- "updates data" --> AttachmentService
  AttachmentService-- "stores update" --> GapDatabase

  classDef focusSystem fill:#1168bd,stroke:#0b4884,color:#ffffff

  class UploadLambda focusSystem

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Deploy the sample application

The Serverless Application Model Command Line Interface (SAM CLI) is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda. It can also emulate your application's build environment and API.

To build the lambda:

sam build

This will build a docker image from a Dockerfile and then copy the source of your application inside the Docker image.

To deploy the lambda:

sam deploy --guided

This will package and deploy your application to AWS, with a series of prompts:

• Stack Name: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
• AWS Region: The AWS region you want to deploy your app to.
• Confirm changes before deploy: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
• Allow SAM CLI IAM role creation: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modifies IAM roles, the CAPABILITY_IAM value for capabilities must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass --capabilities CAPABILITY_IAM to the sam deploy command.
• Save arguments to samconfig.toml: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run sam deploy without parameters to deploy changes to your application.

You can find your API Gateway Endpoint URL in the output values displayed after deployment.

Use the SAM CLI to build and test locally

Build your application with the sam build command.

gap-lambda-upload$ sam build

The SAM CLI builds a docker image from a Dockerfile and then installs dependencies defined in upload_function/requirements.txt inside the docker image. The processed template file is saved in the .aws-sam/build folder.

Test a single function by invoking it directly with a test event. An event is a JSON document that represents the input that the function receives from the event source. Test events are included in the events folder in this project.

Run functions locally and invoke them with the sam local invoke command.

gap-lambda-upload$ sam local invoke UploadFunction --event events/event.json

Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called sam logs. sam logs lets you fetch logs generated by your deployed Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

NOTE: This command works for all AWS Lambda functions; not just the ones you deploy using SAM.

gap-lambda-upload$ sam logs -n UploadFunction --stack-name gap-lambda-upload --tail

Unit tests

Tests are defined in the tests folder in this project. Use PIP to install the pytest and run unit tests from your local machine.

gap-lambda-upload$ pip3 install pytest pytest-mock --user
gap-lambda-upload$ python -m pytest tests/ -v

Cleanup

To delete the sample application that you created, use the AWS CLI. Assuming you used your project name for the stack name, you can run the following:

aws cloudformation delete-stack --stack-name gap-lambda-upload