feat(flags): Attach requestId to $feature_flag_called if present in /decide response (#418)

Author: havenbarnes

posthog-core/src/index.ts

@@ -335,21 +335,28 @@ export abstract class PostHogCoreStateless {
     personProperties: Record<string, string> = {},
     groupProperties: Record<string, Record<string, string>> = {},
     disableGeoip?: boolean
-  ): Promise<boolean | string | undefined> {
+  ): Promise<{
+    response: boolean | string | undefined
+    requestId: string | undefined
+  }> {
     await this._initPromise
 
-    const featureFlags = await this.getFeatureFlagsStateless(
+    const decideResponse = await this.getFeatureFlagsStateless(
       distinctId,
       groups,
       personProperties,
       groupProperties,
       disableGeoip,
       [key]
     )
+    const featureFlags = decideResponse.flags
 
     if (!featureFlags) {
       // If we haven't loaded flags yet, or errored out, we respond with undefined
-      return undefined
+      return {
+        response: undefined,
+        requestId: undefined,
+      }
     }
 
     let response = featureFlags[key]
@@ -361,7 +368,10 @@ export abstract class PostHogCoreStateless {
     }
 
     // If we have flags we either return the value (true or string) or false
-    return response
+    return {
+      response,
+      requestId: decideResponse.requestId,
+    }
   }
 
   protected async getFeatureFlagPayloadStateless(
@@ -436,19 +446,21 @@ export abstract class PostHogCoreStateless {
     groupProperties: Record<string, Record<string, string>> = {},
     disableGeoip?: boolean,
     flagKeysToEvaluate?: string[]
-  ): Promise<PostHogDecideResponse['featureFlags'] | undefined> {
+  ): Promise<{
+    flags: PostHogDecideResponse['featureFlags'] | undefined
+    payloads: PostHogDecideResponse['featureFlagPayloads'] | undefined
+    requestId: PostHogDecideResponse['requestId'] | undefined
+  }> {
     await this._initPromise
 
-    return (
-      await this.getFeatureFlagsAndPayloadsStateless(
-        distinctId,
-        groups,
-        personProperties,
-        groupProperties,
-        disableGeoip,
-        flagKeysToEvaluate
-      )
-    ).flags
+    return await this.getFeatureFlagsAndPayloadsStateless(
+      distinctId,
+      groups,
+      personProperties,
+      groupProperties,
+      disableGeoip,
+      flagKeysToEvaluate
+    )
   }
 
   protected async getFeatureFlagsAndPayloadsStateless(
@@ -461,6 +473,7 @@ export abstract class PostHogCoreStateless {
   ): Promise<{
     flags: PostHogDecideResponse['featureFlags'] | undefined
     payloads: PostHogDecideResponse['featureFlagPayloads'] | undefined
+    requestId: PostHogDecideResponse['requestId'] | undefined
   }> {
     await this._initPromise
 
@@ -481,6 +494,7 @@ export abstract class PostHogCoreStateless {
       return {
         flags: undefined,
         payloads: undefined,
+        requestId: decideResponse?.requestId,
       }
     }
 
@@ -496,6 +510,7 @@ export abstract class PostHogCoreStateless {
     return {
       flags,
       payloads: parsedPayloads,
+      requestId: decideResponse?.requestId,
     }
   }
 

posthog-core/src/types.ts

@@ -126,6 +126,7 @@ export type PostHogDecideResponse = {
     | {
         [key: string]: JsonType
       }
+  requestId?: string
 }
 
 export type PostHogFlagsAndPayloadsResponse = {

posthog-node/CHANGELOG.md

@@ -1,5 +1,9 @@
 # Next
 
+# 4.10.0 – 2025-03-06
+
+1. Attach requestId to $feature_flag_called if present in /decide response
+
 # 4.9.0 – 2025-03-04
 
 1. Allow feature flags to be evaluated individually when local evaluation is not being used

posthog-node/package.json

@@ -1,6 +1,6 @@
 {
   "name": "posthog-node",
-  "version": "4.9.0",
+  "version": "4.10.0",
   "description": "PostHog Node.js integration",
   "repository": {
     "type": "git",

posthog-node/src/posthog-node.ts

@@ -130,12 +130,12 @@ export class PostHog extends PostHogCoreStateless implements PostHogNodeV1 {
       super.captureStateless(distinctId, event, props, { timestamp, disableGeoip, uuid })
     }
 
-    const _getFlags = (
+    const _getFlags = async (
       distinctId: EventMessage['distinctId'],
       groups: EventMessage['groups'],
       disableGeoip: EventMessage['disableGeoip']
     ): Promise<PostHogDecideResponse['featureFlags'] | undefined> => {
-      return super.getFeatureFlagsStateless(distinctId, groups, undefined, undefined, disableGeoip)
+      return (await super.getFeatureFlagsStateless(distinctId, groups, undefined, undefined, disableGeoip)).flags
     }
 
     // :TRICKY: If we flush, or need to shut down, to not lose events we want this promise to resolve before we flush
@@ -260,16 +260,18 @@ export class PostHog extends PostHogCoreStateless implements PostHogNodeV1 {
     )
 
     const flagWasLocallyEvaluated = response !== undefined
-
+    let requestId = undefined
     if (!flagWasLocallyEvaluated && !onlyEvaluateLocally) {
-      response = await super.getFeatureFlagStateless(
+      const remoteResponse = await super.getFeatureFlagStateless(
         key,
         distinctId,
         groups,
         personProperties,
         groupProperties,
         disableGeoip
       )
+      response = remoteResponse.response
+      requestId = remoteResponse.requestId
     }
 
     const featureFlagReportedKey = `${key}_${response}`
@@ -295,6 +297,7 @@ export class PostHog extends PostHogCoreStateless implements PostHogNodeV1 {
           $feature_flag_response: response,
           locally_evaluated: flagWasLocallyEvaluated,
           [`$feature/${key}`]: response,
+          $feature_flag_request_id: requestId,
         },
         groups,
         disableGeoip,