The Overview walked through a simple “Hello World” example. In this section we’ll cover how Sparta works in preparation for moving on to more advanced use. Most development will use the provision command line argument, so this section will outline exactly what that entails.
The provisioning workflow is defined in provision.go, with a goal of marshalling all AWS operations into a CloudFormation template. Where CloudFormation does not support a given service, Sparta falls back to using Lambda-backed Custom Resources in the template definition.
At a high level, provisioning uses the flow below. We’ll dive a bit deeper into each stage in the following sections.
The NewAWSLambda function accepts either a string or a sparta.IAMRoleDefinition value type. In the event that a string is passed, this function verifies that the IAM role exists and builds up a cache of IAM role information that can be shared and referenced during template generation. Specifically, a pre-existing IAM Role ARN is cached to minimize AWS calls during template generation.
The next step is to cross compile the application to a binary that can be executed on an AWS Lambda instance. The default compile flags are:
-tags lambdabinaryGOOS=linux GOARCH=amd64The build output is created in the _./.sparta/ working directory. The full set of build flags is available by running the provision workflow with the --level debug option.
The end result of the package phase is a ZIP archive of your application. You can inspect this archive, as well as any other Sparta artifacts in the ./.sparta directory by supplying the --noop argument during a provision operation.
Uploads the archive to S3. There’s not much else to see here.
Uploading the archive produces a valid CodeURI value that can be used for Lambda function creation. The CloudFormation template is generated by marshaling the sparta.LambdaAWSInfo objects into CloudFormation JSON representations.
The AWS Lambda marshaling is automatically handled. This is also the point at which the optional TemplateDecorator functions are called to annocate the automatically generated template with additional resources.
Uploads the template to S3 to maximize template size. There’s not much else to see here.
Finally, the provisioning workflow determines whether the Sparta serviceName exists and either creates or updates as appropriate using CloudFormation APIs.
Now that we’ve covered how Sparta handles provisioning your stack, we’re ready to expand functionality to leverge more of the AWS ecosystem in the next section.