This project template illustrates the design pattern for subscription style business logic.

You might compare this to similar projects in our Go, Java, Python and PHP SDKs.

Project Specifications

Your task is to write a Workflow for a limited time Subscription (eg a 36 month Phone plan) that satisfies these conditions:

1. When the user signs up, send a welcome email and start a free trial for trialPeriod.
2. If the user cancels during the trial, send a trial cancellation email and complete the Workflow. Liekewise, if the trialPeriod expires, start the billing process.
3. Billing Process:
   • As long as you have not exceeded maxBillingPeriods,
   • Charge the customer for the billingPeriodChargeAmount.
   • Then wait for the next billingPeriod.
   • If the customer cancels during a billing period, send a subscription cancellation email.
   • If Subscription has ended normally (exceeded maxBillingPeriods without cancellation), send a subscription ended email and complete the Workflow.
4. At any point while subscriptions are ongoing, be able to look up and change any customer's:
   • Amount Charged
   • Period number (for manual adjustments e.g. refunds)

Of course, this all has to be fault tolerant, scalable to millions of customers, testable, maintainable!

Tutorial

The guided tutorial for writing this on your own can be found here.

Setup

1. Start by running the Temporal Server in one terminal window: temporal server start-dev --ui-port 8080 --db-filename clusterdata.db. For more details on this command, please refer to the Set up a local development environment for Temporal and TypeScript tutorial here.

2. In another terminal window, run npm install to install dependencies. Then, start the Worker by running npm run start.watch.

3. In another terminal window, run the Workflow Execution with npm run workflow.

This will start the Workflow Executions for 5 customers in parallel. You will see the result of the Activity calls in the terminal Window your Worker is running:

Sending welcome email to email-1@customer.com
Sending welcome email to email-2@customer.com
Sending welcome email to email-4@customer.com
Sending welcome email to email-5@customer.com
Sending welcome email to email-3@customer.com

Each of their periods and charges are varied on purpose to simulate real life variation. After their "trial" period, each customer will be charged:

Charging email-1@customer.com amount 130 for their billing period
Charging email-2@customer.com amount 140 for their billing period
Charging email-3@customer.com amount 150 for their billing period
Charging email-4@customer.com amount 160 for their billing period
Charging email-5@customer.com amount 170 for their billing period

If you let this run to completion, the Workflow Executions complete and report their results back:

Workflow result Completed SubscriptionsWorkflowId-1, Total Charged: 390
Workflow result Completed SubscriptionsWorkflowId-2, Total Charged: 420
Workflow result Completed SubscriptionsWorkflowId-3, Total Charged: 450
Workflow result Completed SubscriptionsWorkflowId-4, Total Charged: 580
Workflow result Completed SubscriptionsWorkflowId-5, Total Charged: 510

Get billing info

You can Query the Workflow Executions and get the billing information for each customer. Do this by running the following command:

npm run querybillinginfo

You can run this after execution completes, or during execution to see the billing period number increase during the executions or see the total charged amount thus far.

Workflow Id subscription-ABC123
Billing Period 2
Total Charged Amount 100
Workflow Id subscription-ABC123
Billing Period 3
Total Charged Amount 200
# etc.

Update billing

You can send a Signal a Workflow Execution to update the billing cycle cost to 300 for all customers. Do this by running the following command:

npm run updatechargeamount

This will update all customer's charge amount to 300:

subscription-ABC123 updating BillingPeriodChargeAmount to 300

Cancel subscription

You can send a Signal to all Workflow Executions to cancel the subscription for all customers. The Workflow Executions will complete after the currently executing billing period. Do this by running the command:

npm run cancelsubscription

This will cancel the subscription to the user supplied in the Client:

Subscription finished for: ABC123

After running this, check out the Temporal Web UI and see that all subscription Workflow Executions have a "Completed" status.