Restate Holiday

This repository demonstrates a complex workflow on Restate with AWS Lambda. The example is based on AWS's Step Functions sample implementation of a Holiday booking service using the Saga pattern.

The goal of this example is to show how you can easily move a fairly complex AWS Step Functions workflow into code using Restate. Instead of designing a graph of operations including failure compensations, you can just execute steps imperatively, using try/catch/finally statements to do error control. You also don't need to make a distinction between workflow and lambda code; everything is Lambda.

The original example has 9 Lambdas:

• Reserve/Confirm/Cancel flight
• Reserve/Confirm/Cancel car reservation
• Process/Refund payment
• Kick off the workflow (called by API gateway)

And some other components:

• API Gateway
• A Step Function with 12 steps

Instead, we have 4 Lambda deployments, each corresponding to a single service from the domain:

• The Trip service, the entrypoint which orchestrates the whole thing, which you can call directly via the Restate HTTP ingress endpoint
• The Flight service, with methods for reserve/confirm/cancel
• The Car service, with methods for reserve/confirm/cancel
• The Payment service, with methods for process/refund

Prerequisites

This example assumes you have the following installed:

• A current version of Node.js and npm
• An AWS account and sufficient permissions to deploy the required resources
• AWS CLI
• curl

Deploying the Holiday Service and a self-hosted Restate instance

By default, the Holiday CDK app will deploy two stacks: a self-hosted Restate instance, and the Holiday service stack.

npx cdk deploy --context deploySelfHostedRestateEnvironment=true

Note the ingress endpoint URL output by the deployment - we will need this later on.

export INGRESS=$(aws cloudformation describe-stacks \
    --stack-name RestateStack \
    --query "Stacks[0].Outputs[?OutputKey=='RestateIngressUrl'].OutputValue" \
    --output text)

Cleanup

When you are done testing, you can easily delete all created resources with the command (if you specified a prefix during deployment, you will need to use the same value here too):

npx cdk destroy --all

Deploying on Restate Cloud

Visit the Restate website to register for a Cloud account which allows you to create a free environment. Create an API key with either Admin or Full access role.

Create a secret in Secrets Manager to hold the authentication token. You can use the following command to save the key in Secrets Manager.

export AUTH_TOKEN_ARN=$(aws secretsmanager create-secret \
    --name /restate-holiday/auth-token --secret-string ${RESTATE_AUTH_TOKEN} \
    --query ARN --output text
)

Once you have the ARN for the secret, deploying the Holiday demo app is as easy as:

npx cdk deploy \
    --context cloudEnvironmentId=${ENVIRONMENT_ID} \
    --context authTokenSecretArn=${AUTH_TOKEN_ARN}

Just like with the self-hosted stack you can also specify a unique prefix if you wish to deploy multiple copies of these stacks to the same AWS account with --context prefix=${USER}. You can also save these context attributes in the cdk.json file to avoid repetition for subsequent CDK operations.

You can obtain the Restate ingress URL from the Restate Cloud UI.

export INGRESS=https://...

You are now ready to jump to Invoking and send some requests to the service.

See the Restate Cloud documentation for more information about deploying to it.

Cleanup

When you are done testing, you can easily delete all created resources with the command (if you specified a prefix or a deployment mode during deployment, you will need to use the same values here too):

npx cdk destroy \
    --context cloudEnvironmentId=${ENVIRONMENT_ID} \
    --context authTokenSecretArn=${AUTH_TOKEN_ARN}

Deploying against local Restate

Restate services don't care if they're running in a Lambda or not. You can start a local instance of the service and use local AWS credentials to interact with AWS resources.

# get stack outputs into your shell
eval $(aws cloudformation describe-stacks --stack RestateHolidayStack  --query "Stacks[].Outputs[]" | jq -r '.[] | "export " + .ExportName + "=" + .OutputValue')
FLIGHTS_TABLE_NAME=${flightsTableName} CARS_TABLE_NAME=${carsTableName} PAYMENTS_TABLE_NAME=${paymentsTableName} npm run app-dev

And you can start a local Restate instance and discover the service:

npx run @restatedev/restate-server

In another shell, register the locally running service endpoint with Restate:

npx run @restatedev/restate deployments register http://localhost:9080

Invoking

Note that we use the -k flag to skip certificate validation and make requests work against an ingress endpoint using a self-signed certificate. If you are calling Restate Cloud, or have a valid certificate deployed in front of your Restate ingress, you can omit this flag.

curl -k ${INGRESS}/trips/reserve --json '{}'

You can cause a specific type of failure by making a request with one of the following failure types:

• failFlightsReservation
• failFlightsConfirmation
• failCarRentalReservation
• failCarRentalConfirmation
• failPayment
• failNotification

curl -k ${INGRESS}/trips/reserve --json '{"request": {"run_type": "failPayment"}}'

You may also provide a trip ID of your choice:

curl -k ${INGRESS}/trips/reserve --json '{"request": {"trip_id": "foo"}}'

Finally, you can make an idempotent invocation by setting the idempotency-key header:

curl -k ${INGRESS}/trips/reserve -H 'idempotency-key: <unique-key>' --json '{}'

Observability

Logs

The Restate container deployed by the CDK construct will publish its logs to CloudWatch logs. You can view them in the console or follow them from a terminal using the AWS CLI:

aws logs tail /restate-holiday/restate-server --follow

If you specified a deployment prefix, the log group will be called /restate/<prefix>/restate.

Traces

The self-hosted Restate container is configured to send traces to AWS X-Ray, by way of the AWS Distro for OpenTelemetry. You should see traces in the X-Ray console including for health checks made by the load balancer. To filter just the traces made to the demo Trips service, use a query like:

service(id(name: "trips"))