ensure metrics are recorded only once

Author: jsumners-nr

lib/subscribers/record-supportability-metric.js

@@ -26,10 +26,14 @@ function recordSupportabilityMetric({
   let metric = agent.metrics.getOrCreateMetric(
     `${SUBSCRIBER_USED}/${moduleName}/${major}`
   )
-  metric.incrementCallCount()
+  if (metric.callCount === 0) {
+    metric.incrementCallCount()
+  }
 
   metric = agent.metrics.getOrCreateMetric(
     `${SUBSCRIBER_USED}/${moduleName}`
   )
-  metric.incrementCallCount()
+  if (metric.callCount === 0) {
+    metric.incrementCallCount()
+  }
 }

test/lib/agent_helper.js

@@ -436,6 +436,19 @@ helper.makeGetRequest = (url, options, callback) => {
  */
 helper.makeGetRequestAsync = util.promisify(helper.makeGetRequest)
 
+helper.asyncHttpCall = function (url, options) {
+  return new Promise((resolve, reject) => {
+    helper.makeRequest(url, options || {}, callback)
+
+    function callback (error, incomingMessage, body) {
+      if (error) {
+        return reject(error)
+      }
+      resolve({ response: incomingMessage, body })
+    }
+  })
+}
+
 helper.makeRequest = (url, options, callback) => {
   if (!options || typeof options === 'function') {
     callback = options

test/versioned/fastify/package.json

@@ -61,6 +61,14 @@
         "errors.test.js",
         "new-state-tracking.test.js"
       ]
+    },
+
+    {
+      "engines": { "node": ">=20" },
+      "dependencies": {
+        "fastify": ">=5.0.0"
+      },
+      "files": [ "usage-metric.test.js" ]
     }
   ]
 }

test/versioned/fastify/usage-metric.test.js

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2026 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+
+const test = require('node:test')
+const helper = require('../../lib/agent_helper')
+
+test('only records one usage metric', async (t) => {
+  t.plan(4)
+
+  const agent = helper.instrumentMockedAgent()
+  const fastify = require('fastify')
+  const pkg = require('fastify/package.json')
+  const version = Number(pkg.version.split('.', 1))
+  const keyBase = 'Supportability/Features/Instrumentation/SubscriberUsed/fastify'
+  const server = fastify({ logger: false })
+
+  t.after(() => {
+    helper.unloadAgent(agent)
+    server.close()
+  })
+
+  server.decorate('test', {
+    getter() {
+      return this._test
+    },
+    setter(value) {
+      this._test = value
+    }
+  })
+
+  server.addHook('preHandler', function(req, res, done) {
+    this.test = true
+    done()
+  })
+
+  server.route({
+    path: '/',
+    method: 'get',
+    handler (req, res) {
+      t.assert.equal(this.test, true)
+      res.send('ok')
+    }
+  })
+
+  const address = await server.listen({ port: 0 })
+
+  agent.on('transactionFinished', () => {
+    const metrics = agent.metrics._metrics.unscoped
+    t.assert.equal(metrics[keyBase].callCount, 1)
+    t.assert.equal(metrics[`${keyBase}/${version}`].callCount, 1)
+  })
+
+  const { body } = await helper.asyncHttpCall(address)
+  t.assert.equal(body, 'ok')
+})