kappa

Kappa is a command line tool that (hopefully) makes it easier to deploy, update, and test functions for AWS Lambda.

There are quite a few steps involved in developing a Lambda function. You have to:

• Write the function itself (Javascript only for now)
• Create the IAM role required by the Lambda function itself (the executing role) to allow it access to any resources it needs to do its job
• Add additional permissions to the Lambda function if it is going to be used in a Push model (e.g. S3, SNS) rather than a Pull model.
• Zip the function and any dependencies and upload it to AWS Lambda
• Test the function with mock data
• Retrieve the output of the function from CloudWatch Logs
• Add an event source to the function
• View the output of the live function

Kappa tries to help you with some of this. It allows you to create an IAM managed policy or use an existing one. It creates the IAM execution role for you and associates the policy with it. Kappa will zip up the function and any dependencies and upload them to AWS Lambda. It also sends test data to the uploaded function and finds the related CloudWatch log stream and displays the log events. Finally, it will add the event source to turn your function on.

If you need to make changes, kappa will allow you to easily update your Lambda function with new code or update your event sources as needed.

Getting Started

Kappa is a command line tool. The basic command format is:

kappa <path to config file> <command> [optional command args]

Where command is one of:

• deploy - does whatever is required to deploy the current version of your Lambda function such as creating/updating policies and roles and creating or updating the function itself
• delete - delete the Lambda function, remove any event sources, delete the IAM policy and role
• invoke - make a synchronous call to your Lambda function, passing test data and display the resulting log data
• invoke_async - make an asynchronous call to your Lambda function passing test data.
• dryrun - make the call but only check things like permissions and report back. Don't actually run the code.
• tail - display the most recent log events for the function (remember that it can take several minutes before log events are available from CloudWatch)
• add_event_sources - hook up an event source to your Lambda function
• update_event_sources - Update the event sources based on the information in your kappa config file
• status - display summary information about functions, stacks, and event sources related to your project.

The config file is a YAML format file containing all of the information about your Lambda function.

If you use environment variables for your AWS credentials (as normally supported by boto), simply exclude the profile element from the YAML file.

An example project based on a Kinesis stream can be found in samples/kinesis.

The basic workflow is:

• Create your Lambda function
• Create any custom IAM policy you need to execute your Lambda function
• Create some sample data
• Create the YAML config file with all of the information
• Run kappa <path-to-config> deploy to create roles and upload function
• Run kappa <path-to-config> test to invoke the function with test data
• Run kappa <path-to-config> deploy to upload new code for your Lambda function
• Run kappa <path-to-config> add_event_sources to hook your function up to the event source
• Run kappa <path-to-config> tail to see more output