async-invoke

AWS Lambda Asynchronous Invocation

This is a example of AWS Lambda Asynchronous Invocation with Python CDK.

The cdk.json file tells the CDK Toolkit how to execute your app.

This project is set up like a standard Python project. The initialization process also creates a virtualenv within this project, stored under the .venv directory. To create the virtualenv it assumes that there is a python3 (or python for Windows) executable in your path with access to the venv package. If for any reason the automatic creation of the virtualenv fails, you can create the virtualenv manually.

To manually create a virtualenv on MacOS and Linux:

$ python3 -m venv .venv

After the init process completes and the virtualenv is created, you can use the following step to activate your virtualenv.

$ source .venv/bin/activate

If you are a Windows platform, you would activate the virtualenv like this:

% .venv\Scripts\activate.bat

Once the virtualenv is activated, you can install the required dependencies.

(.venv) $ pip install -r requirements.txt

At this point you can now synthesize the CloudFormation template for this code.

(.venv) $ export CDK_DEFAULT_ACCOUNT=$(aws sts get-caller-identity --query Account --output text)
(.venv) $ export CDK_DEFAULT_REGION=$(curl -s 169.254.169.254/latest/dynamic/instance-identity/document | jq -r .region)
(.venv) $ cdk synth --all

Use cdk deploy command to create the stack shown above.

(.venv) $ cdk deploy --all

To add additional dependencies, for example other CDK libraries, just add them to your setup.py file and rerun the pip install -r requirements.txt command.

Verify

If you want to test asychronous lambda invocation, run send_sns.py script on the EC2 instance by entering the following command:

(.venv) $ cd ..
(.venv) $ ls src/utils/
send_sns.py
(.venv) $ python src/utils/send_sns.py # do asynchronous invocation on success
(.venv) $ python src/utils/send_sns.py --on-failure # do asynchronous invocation on failure

If you would like to know more about the usage of this command, you can type

(.venv) $ python src/utils/send_sns.py --help

Clean Up

Delete the CloudFormation stack by running the below command.

(.venv) $ cdk destroy --force --all

Useful commands

• cdk ls list all stacks in the app
• cdk synth emits the synthesized CloudFormation template
• cdk deploy deploy this stack to your default AWS account/region
• cdk diff compare deployed stack with current state
• cdk docs open CDK documentation

Gotchas

• You CANNOT test destinations with the "Test" button in the AWS Web console, only CLI calls of the Event type.
  For example,

  aws lambda invoke \
     --function-name my-function \
     --invocation-type Event \
     --cli-binary-format raw-in-base64-out \
     --payload '{ "key": "value" }' response.json
  

Learn more

• Introducing AWS Lambda Destinations
• Understanding the Different Ways to Invoke Lambda Functions
• Lambda Destinations: What We Learned the Hard Way
• Using AWS Lambda with other services

Enjoy!