feat(openfeature): support agentless feature flag configuration (#9397)

Feature flag configuration can now be delivered from the agentless endpoint while keeping startup lazy and polling cancellable. The source retains the last known-good response when polling fails and avoids assembling unrelated JSON fields during streaming responses.

Author: leoromanovsky

.github/CODEOWNERS

@@ -370,6 +370,8 @@
 /packages/dd-trace/src/bootstrap.js @DataDog/lang-platform-js
 /packages/dd-trace/src/feature-registry.js @DataDog/lang-platform-js
 /packages/dd-trace/src/exporters/common/ @DataDog/lang-platform-js
+/packages/dd-trace/src/exporters/common/client-library-headers.js @DataDog/lang-platform-js @DataDog/feature-flagging-and-experimentation-sdk
+/packages/dd-trace/src/proxy.js @DataDog/lang-platform-js
 /packages/dd-trace/test/agent/ @DataDog/lang-platform-js
 /packages/dd-trace/test/dd-trace.spec.js @DataDog/lang-platform-js
 /packages/dd-trace/test/dogstatsd.spec.js @DataDog/lang-platform-js

index.d.ts

@@ -156,12 +156,12 @@ interface Tracer extends opentracing.Tracer {
   llmobs: tracer.llmobs.LLMObs;
 
   /**
-   * OpenFeature Provider with Remote Config integration.
+   * OpenFeature Provider with agentless and Agent Remote Config delivery.
    *
-   * Extends DatadogNodeServerProvider with Remote Config integration for dynamic flag configuration.
-   * Enable with DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED=true.
+   * Agentless delivery is enabled by default and starts when the provider is first accessed.
    *
-   * @env DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED
+   * @env DD_FEATURE_FLAGS_ENABLED
+   * @env DD_FEATURE_FLAGS_CONFIGURATION_SOURCE
    * @beta This feature is in preview and not ready for production use
    */
   openfeature: tracer.OpenFeatureProvider;
@@ -799,9 +799,9 @@ declare namespace tracer {
        */
       flaggingProvider?: {
         /**
-         * Whether to enable the feature flagging provider.
-         * Requires Remote Config to be properly configured.
-         * Can be configured via DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED environment variable.
+         * Legacy feature flagging provider switch.
+         * When the stable Feature Flags configuration is unset, true selects Agent Remote Config and false disables
+         * the provider.
          *
          * @default false
          * @env DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED
@@ -1620,7 +1620,7 @@ declare namespace tracer {
   /**
    * Flagging Provider (OpenFeature-compatible).
    *
-   * Wraps @datadog/openfeature-node-server with Remote Config integration for dynamic flag configuration.
+   * Wraps @datadog/openfeature-node-server with agentless and Agent Remote Config delivery.
    * Implements the OpenFeature Provider interface for flag evaluation.
    *
    * @beta This feature is in preview and not ready for production use

index.d.v5.ts

@@ -156,12 +156,12 @@ interface Tracer extends opentracing.Tracer {
   llmobs: tracer.llmobs.LLMObs;
 
   /**
-   * OpenFeature Provider with Remote Config integration.
+   * OpenFeature Provider with agentless and Agent Remote Config delivery.
    *
-   * Extends DatadogNodeServerProvider with Remote Config integration for dynamic flag configuration.
-   * Enable with DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED=true.
+   * Agentless delivery is enabled by default and starts when the provider is first accessed.
    *
-   * @env DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED
+   * @env DD_FEATURE_FLAGS_ENABLED
+   * @env DD_FEATURE_FLAGS_CONFIGURATION_SOURCE
    * @beta This feature is in preview and not ready for production use
    */
   openfeature: tracer.OpenFeatureProvider;
@@ -869,9 +869,9 @@ declare namespace tracer {
        */
       flaggingProvider?: {
         /**
-         * Whether to enable the feature flagging provider.
-         * Requires Remote Config to be properly configured.
-         * Can be configured via DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED environment variable.
+         * Legacy feature flagging provider switch.
+         * When the stable Feature Flags configuration is unset, true selects Agent Remote Config and false disables
+         * the provider.
          *
          * @default false
          * @env DD_EXPERIMENTAL_FLAGGING_PROVIDER_ENABLED
@@ -1732,7 +1732,7 @@ declare namespace tracer {
   /**
    * Flagging Provider (OpenFeature-compatible).
    *
-   * Wraps @datadog/openfeature-node-server with Remote Config integration for dynamic flag configuration.
+   * Wraps @datadog/openfeature-node-server with agentless and Agent Remote Config delivery.
    * Implements the OpenFeature Provider interface for flag evaluation.
    *
    * @beta This feature is in preview and not ready for production use

integration-tests/openfeature/app/configuration-source-evaluation.js

@@ -0,0 +1,79 @@
+'use strict'
+
+const tracer = require('dd-trace')
+
+const { once } = require('node:events')
+const http = require('node:http')
+
+const { OpenFeature } = require('@openfeature/server-sdk')
+
+const {
+  TEST_DEFAULT_VALUE,
+  TEST_FLAG_KEY,
+  TEST_SERVICE,
+  TEST_TARGETING_KEY,
+} = process.env
+
+tracer.init({
+  env: 'integration',
+  flushInterval: 0,
+  service: TEST_SERVICE,
+})
+
+let client
+
+/**
+ * @param {object} message
+ * @param {'access'|'evaluate'|'trace'} message.command
+ * @param {string} [message.spanName]
+ * @param {string} [message.url]
+ * @param {boolean} [message.waitForReady]
+ */
+async function handleMessage (message) {
+  try {
+    if (message.command === 'access') {
+      const provider = tracer.openfeature
+      if (message.waitForReady) {
+        await OpenFeature.setProviderAndWait(provider)
+      } else {
+        OpenFeature.setProvider(provider)
+      }
+      client = OpenFeature.getClient()
+      send({ accessed: true })
+      return
+    }
+
+    if (message.command === 'evaluate') {
+      const details = await client.getStringDetails(TEST_FLAG_KEY, TEST_DEFAULT_VALUE, {
+        targetingKey: TEST_TARGETING_KEY,
+        userId: TEST_TARGETING_KEY,
+      })
+      send({ details })
+      return
+    }
+
+    if (message.command === 'trace') {
+      await tracer.trace(message.spanName, async () => {
+        if (message.url) {
+          const request = http.get(message.url)
+          const [response] = await once(request, 'response')
+          response.resume()
+          await once(response, 'end')
+        }
+      })
+      send({ traced: true })
+    }
+  } catch (error) {
+    send({ error: error.stack || error.message })
+  }
+}
+
+/**
+ * @param {object} message
+ */
+function send (message) {
+  process.send?.({ port: 0, ...message })
+}
+
+process.on('message', handleMessage)
+send({ ready: true })