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This example demonstrates a payment retry process using Upstash Workflow. The following example handles retrying a payment, sending emails, and suspending accounts.

​
Use Case

Our workflow will:
  1. Attempt to process a payment
  2. Retry the payment if it fails with a 24-hour delay
  3. If the payment succeeds:
    • Unsuspend the user’s account if it was suspended
    • Send an invoice email
  4. If the payment fails after 3 retries:
    • Suspend the user’s account

​
Code Example

import { serve } from "@upstash/workflow/nextjs";

type ChargeUserPayload = {
  email: string;
};

export const { POST } = serve<ChargeUserPayload>(async (context) => {
  const { email } = context.requestPayload;

  for (let i = 0; i < 3; i++) {
    // attempt to charge the user
    const result = await context.run("charge customer", async () => {
      try {
        return await chargeCustomer(i + 1),
      } catch (e) {
        console.error(e);
        return
      }
    });

    if (!result) {
      // Wait for a day
      await context.sleep("wait for retry", 24 * 60 * 60);
    } else {
      // Unsuspend User
      const isSuspended = await context.run("check suspension", async () => {
        return await checkSuspension(email);
      });
      if (isSuspended) {
        await context.run("unsuspend user", async () => {
          await unsuspendUser(email);
        });
      }

      // send invoice email
      await context.run("send invoice email", async () => {
        await sendEmail(
          email,
          `Payment successful. Invoice: ${result.invoiceId}, Total cost: $${result.totalCost}`
        );
      });

      // by returning, we end the workflow run
      return;
    }
  }

  // suspend user if the user isn't suspended
  const isSuspended = await context.run("check suspension", async () => {
    return await checkSuspension(email);
  });

  if (!isSuspended) {
    await context.run("suspend user", async () => {
      await suspendUser(email);
    });

    await context.run("send suspended email", async () => {
      await sendEmail(
        email,
        "Your account has been suspended due to payment failure. Please update your payment method."
      );
    });
  }
});

async function sendEmail(email: string, content: string) {
  // Implement the logic to send an email
  console.log("Sending email to", email, "with content:", content);
}

async function checkSuspension(email: string) {
  // Implement the logic to check if the user is suspended
  console.log("Checking suspension status for", email);
  return true;
}

async function suspendUser(email: string) {
  // Implement the logic to suspend the user
  console.log("Suspending the user", email);
}

async function unsuspendUser(email: string) {
  // Implement the logic to unsuspend the user
  console.log("Unsuspending the user", email);
}

async function chargeCustomer(attempt: number) {
  // Implement the logic to charge the customer
  console.log("Charging the customer");

  if (attempt <= 2) {
    throw new Error("Payment failed");
  }

  return {
    invoiceId: "INV123",
    totalCost: 100,
  } as const;
}

from fastapi import FastAPI
from typing import TypedDict, Optional
from dataclasses import dataclass
from upstash_workflow.fastapi import Serve
from upstash_workflow import AsyncWorkflowContext

app = FastAPI()
serve = Serve(app)


@dataclass
class ChargeResult:
    invoice_id: str
    total_cost: float


class ChargeUserPayload(TypedDict):
    email: str


async def send_email(email: str, content: str) -> None:
    # Implement the logic to send an email
    print("Sending email to", email, "with content:", content)


async def check_suspension(email: str) -> bool:
    # Implement the logic to check if the user is suspended
    print("Checking suspension status for", email)
    return True


async def suspend_user(email: str) -> None:
    # Implement the logic to suspend the user
    print("Suspending the user", email)


async def unsuspend_user(email: str) -> None:
    # Implement the logic to unsuspend the user
    print("Unsuspending the user", email)


async def charge_customer(attempt: int) -> Optional[ChargeResult]:
    # Implement the logic to charge the customer
    print("Charging the customer")
    if attempt <= 2:
        raise Exception("Payment failed")
    return ChargeResult(invoice_id="INV123", total_cost=100)


@serve.post("/payment-retries")
async def payment_retries(context: AsyncWorkflowContext[ChargeUserPayload]) -> None:
    email = context.request_payload["email"]

    async def _check_suspension() -> bool:
        return await check_suspension(email)

    for i in range(3):
        # attempt to charge the user
        async def _charge_customer() -> Optional[ChargeResult]:
            try:
                return await charge_customer(i + 1)
            except Exception as e:
                print(f"Error: {e}")
                return None

        result = await context.run("charge customer", _charge_customer)

        if not result:
            # Wait for a day
            await context.sleep("wait for retry", 24 * 60 * 60)
        else:
            # Unsuspend User
            is_suspended = await context.run("check suspension", _check_suspension)

            if is_suspended:

                async def _unsuspend_user() -> None:
                    await unsuspend_user(email)

                await context.run("unsuspend user", _unsuspend_user)

            # send invoice email
            async def _send_invoice_email() -> None:
                await send_email(
                    email,
                    f"Payment successful. Invoice: {result.invoice_id}, Total cost: ${result.total_cost}",
                )

            await context.run("send invoice email", _send_invoice_email)

            # by returning, we end the workflow run
            return

    # suspend user if the user isn't suspended
    is_suspended = await context.run("check suspension", _check_suspension)

    if not is_suspended:

        async def _suspend_user() -> None:
            await suspend_user(email)

        await context.run("suspend user", _suspend_user)

        async def _send_suspended_email() -> None:
            await send_email(
                email,
                "Your account has been suspended due to payment failure. Please update your payment method.",
            )

        await context.run("send suspended email", _send_suspended_email)

​
Code Breakdown

​
1. Charge Customer

We attempt to charge the customer: 
const result = await context.run("charge customer", async () => {
  try {
    return await chargeCustomer(i + 1),
  } catch (e) {
    console.error(e);
    return
  }
});

async def _charge_customer() -> Optional[ChargeResult]:
    try:
        return await charge_customer(i + 1)
    except Exception as e:
        print(f"Error: {e}")
        return None

result = await context.run("charge customer", _charge_customer)
If we haven’t put a try-catch block here, the workflow would have retried the step. However, because we want to run custom logic when the payment fails, we catch the error here.

​
2. Retry Payment

We try to charge the customer 3 times with a 24-hour delay between each attempt: 
for (let i = 0; i < 3; i++) {
  // attempt to charge the customer

  if (!result) {
    // Wait for a day
    await context.sleep("wait for retry", 24 * 60 * 60);
  } else {
    // Payment succeeded
    // Unsuspend user, send invoice email
    // end the workflow:
    return;
  }
}

for i in range(3):
    # attempt to charge the customer

    if not result:
        # Wait for a day
        await context.sleep("wait for retry", 24 * 60 * 60)
    else:
        # Payment succeeded
        # Unsuspend user, send invoice email
        # end the workflow:
        return

​
3. If Payment Succeeds

​
3.1. Unsuspend User

We check if the user is suspended and unsuspend them if they are: 
const isSuspended = await context.run("check suspension", async () => {
  return await checkSuspension(email);
});
if (isSuspended) {
  await context.run("unsuspend user", async () => {
    await unsuspendUser(email);
  });
}

async def _check_suspension() -> bool:
    return await check_suspension(email)

is_suspended = await context.run("check suspension", _check_suspension)

if is_suspended:

    async def _unsuspend_user() -> None:
        await unsuspend_user(email)

    await context.run("unsuspend user", _unsuspend_user)

​
3.2. Send Invoice Email

We send an invoice we got from the payment step to the user: 
await context.run("send invoice email", async () => {
  await sendEmail(
    email,
    `Payment successful. Invoice: ${result.invoiceId}, Total cost: $${result.totalCost}`
  );
});

async def _send_invoice_email() -> None:
    await send_email(
        email,
        f"Payment successful. Invoice: {result.invoice_id}, Total cost: ${result.total_cost}",
    )

await context.run("send invoice email", _send_invoice_email)
One of the biggest advantages of using Upstash Workflow is that you have access to the result of the previous steps. This allows you to pass data between steps without having to store it in a database.

​
4. If Payment Fails After 3 Retries

​
4.1. Suspend User

If the payment fails after 3 retries, we suspend the user and send them an email to notify them: 
const isSuspended = await context.run("check suspension", async () => {
  return await checkSuspension(email);
});

if (!isSuspended) {
  await context.run("suspend user", async () => {
    await suspendUser(email);
  });

  await context.run("send suspended email", async () => {
    await sendEmail(
      context.requestPayload.email,
      "Your account has been suspended due to payment failure. Please update your payment method."
    );
  });
}

async def _check_suspension() -> bool:
    return await check_suspension(email)

is_suspended = await context.run("check suspension", _check_suspension)

if not is_suspended:

    async def _suspend_user() -> None:
        await suspend_user(email)

    await context.run("suspend user", _suspend_user)

    async def _send_suspended_email() -> None:
        await send_email(
            email,
            "Your account has been suspended due to payment failure. Please update your payment method.",
        )

    await context.run("send suspended email", _send_suspended_email)