🚀 Module 4: Creating and Deploying Your First Serverless Function

Technology Stack:

• Quarkus
• K-Native Eventing
• Red Hat Serverless
• Quarkus FUNQY
• Kafka

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🎯 Scenario

Company A is sending a payment transaction (credit card) to ACME. ACME has 4 business steps that need to happen for the transaction to be a success.

1. Customer Profile Service System | To check if the customer is a valid customer
2. Fraud Detection System | We need to verify the transaction is not fraudulent
3. Payment Processing System | If the transaction is legitiate, we want to sent it to payments
4. If the payment is successful Ledger Service | We want to capture it as successful Notification Service | And notify the customer.

Our current system has a workflow engine, it is stateful. We want to move it to a process that can be distributed, stateless and fully event driven.

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🧩 Challenge

• Write your own FUNQY event
• Annotate it in the correct part of your workflow
• Wire it up to a K-Native event
• Verify the result in Kafka

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🔄 Transaction Flow Breakdown

1. 🔹 Validate Customer (validateTransaction)

• Triggered by an external Knative CloudEvent (defaultChain), e.g., from a curl call.
• Mocks a call to a Customer Profile Service (verifies customer account is active).
• Marks transaction as VALIDATED.
• Returns a CloudEvent of type fraudCheck.

✨ Example: Creating a CloudEvent | Default Chain

NS=$(oc project -q)

oc exec -it curler -n "$NS" -- curl -v \
  "http://broker-ingress.knative-eventing.svc.cluster.local/${NS}/default" \
  -H "Ce-Id: txn-001" \
  -H "Ce-Specversion: 1.0" \
  -H "Ce-Type: defaultChain" \
  -H "Ce-Source: bash" \
  -H "Content-Type: application/json" \
  -d '{"transactionId":"txn-1001","customerId":"42","amount":12500,"currency":"JPY"}'

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2. 🔸 Fraud Check (fraudCheck)

• Triggered by the fraudCheck function (annotation-based mapping).
• Mocks a Fraud Detection System (rules + ML).
• Business rule:
  • If amount > 10,000 → FLAGGED for manual review.
  • Otherwise → CLEARED.
  • Emits a CloudEvent of type annotated to trigger the processPayment step.

✨ Example: Creating a CloudEvent | Fraud Check

NS=$(oc project -q)

oc exec -it curler -n "$NS" -- curl -v \
  "http://broker-ingress.knative-eventing.svc.cluster.local/${NS}/default" \
  -H "Ce-Id: txn-002" \
  -H "Ce-Specversion: 1.0" \
  -H "Ce-Type: fraudCheck" \
  -H "Ce-Source: bash" \
  -H "Content-Type: application/json" \
  -d '{"transactionId":"txn-1002","customerId":"57","amount":5000,"currency":"USD"}'

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3. 🔹 Payment Processing (processPayment)

• Triggered by the processPayment function (annotation-based mapping).
• Mocks:
  • Core Banking API (debit customer account).
  • Payment Gateway (Visa/MasterCard).
• Marks transaction as PROCESSED.
• Returns a CloudEvent of type lastChainLink.

✨ Example: Creating a CloudEvent | Payment Processing

NS=$(oc project -q)

oc exec -it curler -n "$NS" -- curl -v \
  "http://broker-ingress.knative-eventing.svc.cluster.local/${NS}/default" \
  -H "Ce-Id: txn-003" \
  -H "Ce-Specversion: 1.0" \
  -H "Ce-Type: annotated" \
  -H "Ce-Source: bash" \
  -H "Content-Type: application/json" \
  -d '{"transactionId":"txn-1003","customerId":"99","amount":2000,"currency":"EUR"}'

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4. 🔸 Settlement & Kafka Publish (settleTransaction)

• Triggered by settleTransaction function.
• Mocks:
  • Ledger Service (recording transaction).
  • Notification Service (alerting customer).
• Publishes the finalized transaction to Kafka using

NS=$(oc project -q)

oc exec -it curler -n "$NS" -- curl -v \
  "http://broker-ingress.knative-eventing.svc.cluster.local/${NS}/default" \
  -H "Ce-Id: txn-004" \
  -H "Ce-Specversion: 1.0" \
  -H "Ce-Type: lastChainLink" \
  -H "Ce-Source: bash" \
  -H "Content-Type: application/json" \
  -d '{"transactionId":"txn-1004","customerId":"88","amount":7500,"currency":"GBP","status":"PROCESSED","message":"Payment successfully processed"}'

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✅ Key Takeaways

• You have created a FUNQY Event in Quarkus
• You created a K-Native Event that can respond to triggers and trigger itself
• See how quickly Quarkus can build Serverless Events