The CloudMapServiceDecorator allows your service to register a service instance for your application.
For example, an application that provisions a SQS queue and an AWS Lambda function that consumes messages from that queue may need a way for the Lambda function to discover the dynamically provisioned queue.
Sparta supports an environment-based discovery service but that discovery is limited to a single Service.
The CloudMapServiceDecorator leverages the CloudMap service to support intra- and inter-service resource discovery.
The first step is to create an instance of the CloudMapServiceDecorator type that can be used to register additional resources.
import (
spartaDecorators "github.com/mweagle/Sparta/v3/decorator"
)
func main() {
...
cloudMapDecorator, cloudMapDecoratorErr := spartaDecorators.NewCloudMapServiceDecorator(gocf.String("SpartaServices"),
gocf.String("SpartaSampleCloudMapService"))
...
}
The first argument is the Cloud Map Namespace ID value to which the service (MyService) will publish.
The decorator satisfies the ServiceDecoratorHookHandler. The instance should be provided as a WorkflowHooks.ServiceDecorators element to MainEx as in:
func main() {
// ...
cloudMapDecorator, cloudMapDecoratorErr := spartaDecorators.NewCloudMapServiceDecorator(gocf.String("SpartaServices"),
gocf.String("SpartaSampleCloudMapService"))
workflowHooks := &sparta.WorkflowHooks{
ServiceDecorators: []sparta.ServiceDecoratorHookHandler{
cloudMapDecorator,
},
}
// ...
err := sparta.MainEx(awsName,
"Simple Sparta application that demonstrates core functionality",
lambdaFunctions,
nil,
nil,
workflowHooks,
false)
}
The returned CloudMapServiceDecorator instance satisfies the ServiceDecoratorHookHandler interface. When invoked, it updates the content of you CloudFormation template with the resources and permissions as described below. CloudMapServiceDecorator implicitly creates a new AWS::ServiceDiscovery::Service resource to which your resources will be published.
The CloudMapServiceDecorator.PublishLambda function publishes Lambda function information to the (NamespaceID, ServiceID) pair.
lambdaFn, _ := sparta.NewAWSLambda("Hello World",
helloWorld,
sparta.IAMRoleDefinition{})
cloudMapDecorator.PublishLambda("lambdaDiscoveryName", lambdaFn, nil)
The default properties published include the Lambda Outputs and Type information:
{
"Id": "CloudMapResbe2b7c536074312c-VuIPjfjuFaoc",
"Attributes": {
"Arn": "arn:aws:lambda:us-west-2:123412341234:function:MyHelloWorldStack-123412341234_Hello_World",
"Name": "lambdaDiscoveryName",
"Ref": "MyHelloWorldStack-123412341234_Hello_World",
"Type": "AWS::Lambda::Function"
}
}
The CloudMapServiceDecorator.PublishResource function publishes arbitrary CloudFormation resource outputs information to the (NamespaceID, ServiceID) pair.
For instance, to publish SQS information in the context of a standard ServiceDecorator
func createSQSResourceDecorator(cloudMapDecorator *spartaDecorators.CloudMapServiceDecorator) sparta.ServiceDecoratorHookHandler {
return sparta.ServiceDecoratorHookFunc(func(context map[string]interface{},
serviceName string,
template *gocf.Template,
S3Bucket string,
S3Key string,
buildID string,
awsSession *session.Session,
noop bool,
logger *zerolog.Logger) error {
sqsResource := &gocf.SQSQueue{}
template.AddResource("SQSResource", sqsResource)
return cloudMapDecorator.PublishResource("SQSResource",
"SQSResource",
sqsResource,
nil)
})
}
The default properties published include the SQS Outputs and Type information:
{
"Id": "CloudMapRes21cf275e8bbbe136-CqWZ27gdLHf8",
"Attributes": {
"Arn": "arn:aws:sqs:us-west-2:123412341234:MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Name": "SQSResource",
"QueueName": "MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Ref": "https://sqs.us-west-2.amazonaws.com/123412341234/MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Type": "AWS::SQS::Queue"
}
}
Publishing instances to CloudMap only makes them available for other services to discover them. Call the EnableDiscoverySupport with your *sparta.LambdaAWSInfo instance as the only argument. This function updates your Lambda function’s environment to include the provisioned ServiceInstance and also the IAM role privileges to authorize:
For instance:
func main() {
// ...
lambdaFn, _ := sparta.NewAWSLambda("Hello World",
helloWorld,
sparta.IAMRoleDefinition{})
// ...
cloudMapDecorator.EnableDiscoverySupport(lambdaFn)
// ...
}
With the resources published and the lambda role properly updated, the last step is to dynamically discover the provisioned resources via CloudMap. Call DiscoverInstancesWithContext with the the set of key-value pairs to use for discovery as below:
func helloWorld(ctx context.Context) (string, error) {
// ...
props := map[string]string{
"Type": "AWS::SQS::Queue",
}
results, resultsErr := spartaDecorators.DiscoverInstancesWithContext(ctx,
props,
logger)
logger.Info().
Interface("Instances", results).
Err(resultsErr).
Msg("Discovered instances")
// ...
}
Given the previous example of a single lambda function and an SQS-queue provisioning decorator, the DiscoverInstancesWithContext would return the matching instance with data similar to:
{
"Instances": [
{
"Attributes": {
"Arn": "arn:aws:sqs:us-west-2:123412341234:MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Name": "SQSResource",
"QueueName": "MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Ref": "https://sqs.us-west-2.amazonaws.com/123412341234/MyHelloWorldStack-123412341234-SQSResource-S9DWKIFKP14U",
"Type": "AWS::SQS::Queue"
},
"HealthStatus": "HEALTHY",
"InstanceId": "CloudMapResd1a507076543ccd0-Fln1ITi5cf0y",
"NamespaceName": "SpartaServices",
"ServiceName": "SpartaSampleCloudMapService"
}
]
}