feat(openfeature): select agentless exposure routes

Author: leoromanovsky

.github/CODEOWNERS

@@ -367,6 +367,7 @@
 /integration-tests/import-variants.spec.js @DataDog/lang-platform-js
 /integration-tests/init/ @DataDog/lang-platform-js
 /integration-tests/init.spec.js @DataDog/lang-platform-js
+/integration-tests/helpers/fake-agent.js @DataDog/lang-platform-js @DataDog/feature-flagging-and-experimentation-sdk
 /integration-tests/memory-leak/ @DataDog/lang-platform-js
 /integration-tests/mocha-parallel-files-fixtures/ @DataDog/lang-platform-js
 /integration-tests/mocha-parallel-files.spec.js @DataDog/lang-platform-js

integration-tests/helpers/fake-agent.js

@@ -31,6 +31,7 @@ module.exports = class FakeAgent extends EventEmitter {
   port = 0
   advertiseDebuggerV2IntakeSupport = true
   debuggerV2IntakeStatusCode = 202
+  evpProxyVersions = [2]
   /** @type {Set<import('net').Socket>} */
   #sockets = new Set()
   /** @type {Record<string, RemoteConfigFile>} */
@@ -50,6 +51,9 @@ module.exports = class FakeAgent extends EventEmitter {
     if (options.debuggerV2IntakeStatusCode !== undefined) {
       this.debuggerV2IntakeStatusCode = options.debuggerV2IntakeStatusCode
     }
+    if (options.evpProxyVersions !== undefined) {
+      this.evpProxyVersions = [...options.evpProxyVersions]
+    }
   }
 
   /**
@@ -376,7 +380,10 @@ function buildExpressServer (agent) {
   app.use(bodyParser.json({ limit: Infinity, type: 'application/json' }))
 
   app.get('/info', (req, res) => {
-    const endpoints = ['/evp_proxy/v2', '/debugger/v1/input']
+    const endpoints = [
+      ...agent.evpProxyVersions.map(version => `/evp_proxy/v${version}`),
+      '/debugger/v1/input',
+    ]
     if (agent.advertiseDebuggerV2IntakeSupport) {
       endpoints.push('/debugger/v2/input')
     }
@@ -565,10 +572,14 @@ function buildExpressServer (agent) {
     })
   })
 
-  app.post('/evp_proxy/v2/api/v2/exposures', (req, res) => {
+  app.post([
+    '/evp_proxy/v2/api/v2/exposures',
+    '/evp_proxy/v4/api/v2/exposures',
+  ], (req, res) => {
     res.status(200).send()
     agent.emit('exposures', {
       headers: req.headers,
+      path: req.path,
       payload: req.body,
     })
   })

integration-tests/openfeature/openfeature-exposure-events.spec.js

@@ -54,7 +54,7 @@ describe('OpenFeature Remote Config and Exposure Events Integration', () => {
       let agent, proc
 
       beforeEach(async () => {
-        agent = await new FakeAgent().start()
+        agent = await new FakeAgent(0, { evpProxyVersions: [2, 4] }).start()
         proc = await spawnProc(appFile, {
           cwd,
           env: {
@@ -78,7 +78,7 @@ describe('OpenFeature Remote Config and Exposure Events Integration', () => {
         let receivedAckUpdate = false
 
         // Listen for exposure events
-        agent.on('exposures', ({ payload, headers }) => {
+        agent.on('exposures', ({ payload, headers, path }) => {
           assert.ok(Object.hasOwn(payload, 'exposures'), `Available keys: ${inspect(Object.keys(payload))}`)
           assertObjectContains(payload, {
             context: {
@@ -94,6 +94,7 @@ describe('OpenFeature Remote Config and Exposure Events Integration', () => {
             try {
               assert.strictEqual(headers['content-type'], 'application/json')
               assert.strictEqual(headers['x-datadog-evp-subdomain'], 'event-platform-intake')
+              assert.strictEqual(path, '/evp_proxy/v2/api/v2/exposures')
 
               // Verify we got exposure events from flag evaluations
               assert.strictEqual(exposureEvents.length, 2)

packages/dd-trace/src/openfeature/index.js

@@ -3,7 +3,7 @@
 const { channel } = require('dc-polyfill')
 const log = require('../log')
 const ExposuresWriter = require('./writers/exposures')
-const { setAgentStrategy } = require('./writers/util')
+const { setExposureDeliveryStrategy } = require('./writers/util')
 
 const exposureSubmitCh = channel('ffe:exposure:submit')
 const flushCh = channel('ffe:writers:flush')
@@ -45,10 +45,10 @@ function enable (config) {
   exposureSubmitCh.subscribe(_handleExposureSubmit)
   flushCh.subscribe(_handleFlush)
 
-  setAgentStrategy(config, (hasAgent, route) => {
+  setExposureDeliveryStrategy(config, (enabled, route) => {
     if (exposuresWriter !== writer) return
 
-    writer.setEnabled(hasAgent, route)
+    writer.setEnabled(enabled, route)
   })
 }
 

packages/dd-trace/src/openfeature/writers/util.js

@@ -1,20 +1,44 @@
 'use strict'
 
-const logger = require('../../log')
-const { EVP_PROXY_PATH_V2 } = require('../../evp_proxy/constants')
+const {
+  EVP_EVENT_PLATFORM_SUBDOMAIN,
+  EVP_PROXY_PATH_V2,
+  EVP_PROXY_PATH_V4,
+  EVP_SUBDOMAIN_HEADER_NAME,
+} = require('../../evp_proxy/constants')
+const { createDirectEVPRoute } = require('../../evp_proxy/direct')
 const { discoverEVPProxy } = require('../../evp_proxy/discovery')
+const logger = require('../../log')
+
+let missingRouteWarningLogged = false
+
+/**
+ * Logs the unavailable exposure-delivery warning once.
+ *
+ * @returns {void}
+ */
+function warnExposureDeliveryUnavailable () {
+  if (missingRouteWarningLogged) return
+  missingRouteWarningLogged = true
+  logger.warn(
+    'Feature Flags exposure delivery is disabled because no compatible local EVP route or direct intake ' +
+    'credentials are available.'
+  )
+}
 
 /**
- * Determines if the agent supports EVP proxy and sets the writer enabled state accordingly
+ * Preserves Agent exposure delivery for the Remote Configuration source.
+ *
  * @param {import('../../config')} config - Tracer configuration object
  * @param {Function} setWriterEnabledValue - Callback to set the writer enabled state
+ * @returns {void}
  */
 function setAgentStrategy (config, setWriterEnabledValue) {
   discoverEVPProxy(config.url, {
     supportedPaths: [EVP_PROXY_PATH_V2],
-  }, (err, route) => {
-    if (err) {
-      logger.debug('FFE Writer disabled - error getting agent info: %s', err.message)
+  }, (error, route) => {
+    if (error) {
+      logger.debug('FFE Writer disabled - error getting agent info: %s', error.message)
       setWriterEnabledValue(false)
       return
     }
@@ -29,6 +53,67 @@ function setAgentStrategy (config, setWriterEnabledValue) {
   })
 }
 
-module.exports = {
-  setAgentStrategy,
+/**
+ * Selects a local serverless receiver or authenticated direct intake.
+ *
+ * Local discovery is optional for delivery. A missing listener, discovery
+ * error, or incompatible receiver selects direct intake when credentials exist.
+ *
+ * @param {import('../../config')} config - Tracer configuration object
+ * @param {Function} setWriterEnabledValue - Callback to set the writer enabled state
+ * @returns {void}
+ */
+function setAgentlessStrategy (config, setWriterEnabledValue) {
+  const directRoute = createDirectEVPRoute(config, EVP_EVENT_PLATFORM_SUBDOMAIN)
+
+  discoverEVPProxy(config.url, {
+    supportedPaths: [EVP_PROXY_PATH_V4, EVP_PROXY_PATH_V2],
+  }, (error, localRoute) => {
+    if (localRoute) {
+      const route = {
+        ...localRoute,
+        headers: {
+          [EVP_SUBDOMAIN_HEADER_NAME]: EVP_EVENT_PLATFORM_SUBDOMAIN,
+        },
+        ...(directRoute && { fallback: directRoute }),
+      }
+      logger.debug('FFE Writer enabled with local EVP route %s', route.basePath)
+      setWriterEnabledValue(true, route)
+      return
+    }
+
+    if (directRoute) {
+      if (error) {
+        logger.debug('FFE Writer using direct EVP intake after local discovery failed: %s', error.message)
+      } else {
+        logger.debug('FFE Writer using direct EVP intake because no compatible local route was advertised')
+      }
+      setWriterEnabledValue(true, directRoute)
+      return
+    }
+
+    if (error) {
+      logger.debug('FFE Writer disabled - error getting local receiver info: %s', error.message)
+    }
+    warnExposureDeliveryUnavailable()
+    setWriterEnabledValue(false)
+  })
+}
+
+/**
+ * Applies the exposure-delivery strategy for the configured Feature Flags source.
+ *
+ * @param {import('../../config')} config - Tracer configuration object
+ * @param {Function} setWriterEnabledValue - Callback to set the writer enabled state
+ * @returns {void}
+ */
+function setExposureDeliveryStrategy (config, setWriterEnabledValue) {
+  if (config.featureFlags?.DD_FEATURE_FLAGS_CONFIGURATION_SOURCE === 'agentless') {
+    setAgentlessStrategy(config, setWriterEnabledValue)
+    return
+  }
+
+  setAgentStrategy(config, setWriterEnabledValue)
 }
+
+module.exports = { setExposureDeliveryStrategy }

packages/dd-trace/test/openfeature/index.spec.js

@@ -14,7 +14,7 @@ describe('OpenFeature Module', () => {
   let openfeatureModule
   let mockWriter
   let ExposuresWriterStub
-  let setAgentStrategyStub
+  let setExposureDeliveryStrategyStub
 
   beforeEach(() => {
     config = {
@@ -30,11 +30,11 @@ describe('OpenFeature Module', () => {
     }
 
     ExposuresWriterStub = sinon.stub().returns(mockWriter)
-    setAgentStrategyStub = sinon.stub()
+    setExposureDeliveryStrategyStub = sinon.stub()
 
     openfeatureModule = proxyquire('../../src/openfeature', {
       './writers/exposures': ExposuresWriterStub,
-      './writers/util': { setAgentStrategy: setAgentStrategyStub },
+      './writers/util': { setExposureDeliveryStrategy: setExposureDeliveryStrategyStub },
     })
   })
 
@@ -52,17 +52,17 @@ describe('OpenFeature Module', () => {
       openfeatureModule.enable(config)
 
       sinon.assert.calledOnceWithExactly(ExposuresWriterStub, config)
-      sinon.assert.calledOnce(setAgentStrategyStub)
+      sinon.assert.calledOnce(setExposureDeliveryStrategyStub)
     })
 
-    it('passes the discovered route to the writer', () => {
+    it('configures the writer with the selected exposure route', () => {
+      openfeatureModule.enable(config)
+      const setWriterEnabled = setExposureDeliveryStrategyStub.firstCall.args[1]
       const route = {
-        url: new URL('http://localhost:8126'),
-        basePath: '/evp_proxy/v2',
+        url: new URL('http://serverless-init:8126'),
+        basePath: '/evp_proxy/v4',
       }
-      setAgentStrategyStub.callsArgWith(1, true, route)
-
-      openfeatureModule.enable(config)
+      setWriterEnabled(true, route)
 
       sinon.assert.calledOnceWithExactly(mockWriter.setEnabled, true, route)
     })
@@ -85,10 +85,10 @@ describe('OpenFeature Module', () => {
       ExposuresWriterStub.onSecondCall().returns(replacementWriter)
 
       openfeatureModule.enable(config)
-      const staleCallback = setAgentStrategyStub.firstCall.args[1]
+      const staleCallback = setExposureDeliveryStrategyStub.firstCall.args[1]
       openfeatureModule.disable()
       openfeatureModule.enable(config)
-      const currentCallback = setAgentStrategyStub.secondCall.args[1]
+      const currentCallback = setExposureDeliveryStrategyStub.secondCall.args[1]
 
       staleCallback(true, staleRoute)
       sinon.assert.notCalled(replacementWriter.setEnabled)