[payment] fork friendly hooks

src/payment/charge-hooks.js

@@ -0,0 +1,35 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// This file is meant to be implemented by forks of the OpenTelemetry Demo repository
+// to showcase custom observability functionality implemented by the fork.
+// The OpenTelemetry Demo repository will not modify this file, allowing forks to
+// demonstrate their own unique functionality without merge conflicts.
+
+class chargeHooks {
+  constructor(request) {
+    this.request = request;
+  }
+
+  // The preHook function is called before the charge span is started
+  preHook() {
+
+  }
+
+  // The startHook function is called after the charge span is started
+  startHook() {
+
+  }
+
+  // The endHook function is called before the charge span is ended
+  endHook() {
+
+  }
+
+  // The postHook function is called after the charge span is ended
+  postHook() {
+
+  }
+}
+
+module.exports = chargeHooks;

src/payment/charge.js

@@ -9,6 +9,7 @@ const { FlagdProvider } = require('@openfeature/flagd-provider');
 const flagProvider = new FlagdProvider();
 
 const logger = require('./logger');
+const chargeHooks = require("./charge-hooks");
 const tracer = trace.getTracer('payment');
 const meter = metrics.getMeter('payment');
 const transactionsCounter = meter.createCounter('app.payment.transactions');
@@ -22,8 +23,15 @@ function random(arr) {
 }
 
 module.exports.charge = async request => {
+  const ch = new chargeHooks(request);
+  // call any fork hooks before starting span
+  ch.preHook();
+
   const span = tracer.startSpan('charge');
 
+  // call any fork hooks after starting span
+  ch.startHook();
+
   await OpenFeature.setProviderAndWait(flagProvider);
 
   const numberVariant =  await OpenFeature.getClient().getNumberValue("paymentFailure", 0);
@@ -82,7 +90,14 @@ module.exports.charge = async request => {
   const { units, nanos, currencyCode } = request.amount;
   logger.info({ transactionId, cardType, lastFourDigits, amount: { units, nanos, currencyCode }, loyalty_level }, 'Transaction complete.');
   transactionsCounter.add(1, { 'app.payment.currency': currencyCode });
+
+  // call any fork hooks before ending span
+  ch.endHook();
+
   span.end();
 
+  // call any fork hooks after ending span
+  ch.postHook();
+
   return { transactionId };
 };