Analytics Message: "Cannot get flag for unregistered flag. SDK name, flag name: app_measurement, session_stitching_token_feature_enabled"

[SKuhlemann]

Description

When I create a new Xcode Project with an SwiftUI lifecycle and follow the integration tutorial for Firebase Analytics then I always see the following Debugger message multiple times.
For example when the app goes into inactive or background scenephase:
MyApp[4010:1178178] 10.6.0 - [FirebaseAnalytics][I-ACS800014] Cannot get flag for unregistered flag. SDK name, flag name: app_measurement, session_stitching_token_feature_enabled

This happens on simulator and real devices.

I added "-ObjC" as "Other Linking flags" for the target in XCode.
I also have Background modes enabled for the target:

• Background fetch
• Remote notifications
• Background processing

Below I attached the logging in debugging mode, but the above message also appear in "normal" logging mode.
I dont't see any problems with FirebaseAnalytics and everything seems to be logged fine when taking a look into the Firebase console on the website.
Nevertheless this message makes me suspicious that something is wrong.

Kind regards
Stefan

Reproducing the issue

• Create a new XCode project
• Follow the instruction tutorial form Firebase Analytics for an iOS SwiftUI App
• Run the app and put it into scenephase inactive or background

Firebase SDK Version

10.6.0

Xcode Version

14.2

Installation Method

Swift Package Manager

Firebase Product(s)

Analytics

Targeted Platforms

iOS

Relevant Log Output

2023-03-11 21:37:37.822985+0100 MyApp[10869:7635154] 10.6.0 - [FirebaseAnalytics][I-ACS023087] User property set. Name, value: lifetime_user_engagement (_lte), 92873658
2023-03-11 21:37:37.823493+0100 MyApp[10869:7635154] 10.6.0 - [FirebaseAnalytics][I-ACS023087] User property set. Name, value: session_user_engagement (_se), 5620
2023-03-11 21:37:37.823989+0100 MyApp[10869:7635154] 10.6.0 - [FirebaseAnalytics][I-ACS800014] Cannot get flag for unregistered flag. SDK name, flag name: app_measurement, session_stitching_token_feature_enabled
2023-03-11 21:37:37.824550+0100 MyApp[10869:7635154] 10.6.0 - [FirebaseAnalytics][I-ACS012018] Saving bundle. size (bytes): 546
2023-03-11 21:37:37.825096+0100 MyApp[10869:7635154] 10.6.0 - [FirebaseAnalytics][I-ACS023116] Bundle added to the upload queue. BundleID, timestamp (ms): 364, 1678567057698

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

{
  "pins" : [
    {
      "identity" : "abseil-cpp-swiftpm",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/abseil-cpp-SwiftPM.git",
      "state" : {
        "revision" : "583de9bd60f66b40e78d08599cc92036c2e7e4e1",
        "version" : "0.20220203.2"
      }
    },
    {
      "identity" : "boringssl-swiftpm",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/boringssl-SwiftPM.git",
      "state" : {
        "revision" : "dd3eda2b05a3f459fc3073695ad1b28659066eab",
        "version" : "0.9.1"
      }
    },
    {
      "identity" : "firebase-ios-sdk",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/firebase-ios-sdk.git",
      "state" : {
        "revision" : "60f9a33e7084482df67b48e16f315f4f7a6f5da9",
        "version" : "10.6.0"
      }
    },
    {
      "identity" : "googleappmeasurement",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleAppMeasurement.git",
      "state" : {
        "revision" : "04351180d4c757c6c16127cb57b685fff9ef260b",
        "version" : "10.6.0"
      }
    },
    {
      "identity" : "googledatatransport",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleDataTransport.git",
      "state" : {
        "revision" : "f6b558e3f801f2cac336b04f615ce111fa9ddaa0",
        "version" : "9.2.1"
      }
    },
    {
      "identity" : "googleutilities",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/GoogleUtilities.git",
      "state" : {
        "revision" : "0543562f85620b5b7c510c6bcbef75b562a5127b",
        "version" : "7.11.0"
      }
    },
    {
      "identity" : "grpc-ios",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/grpc/grpc-ios.git",
      "state" : {
        "revision" : "8440b914756e0d26d4f4d054a1c1581daedfc5b6",
        "version" : "1.44.3-grpc"
      }
    },
    {
      "identity" : "gtm-session-fetcher",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/gtm-session-fetcher.git",
      "state" : {
        "revision" : "96d7cc73a71ce950723aa3c50ce4fb275ae180b8",
        "version" : "3.1.0"
      }
    },
    {
      "identity" : "leveldb",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/leveldb.git",
      "state" : {
        "revision" : "0706abcc6b0bd9cedfbb015ba840e4a780b5159b",
        "version" : "1.22.2"
      }
    },
    {
      "identity" : "nanopb",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/nanopb.git",
      "state" : {
        "revision" : "819d0a2173aff699fb8c364b6fb906f7cdb1a692",
        "version" : "2.30909.0"
      }
    },
    {
      "identity" : "promises",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/google/promises.git",
      "state" : {
        "revision" : "ec957ccddbcc710ccc64c9dcbd4c7006fcf8b73a",
        "version" : "2.2.0"
      }
    },
    {
      "identity" : "swift-protobuf",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/apple/swift-protobuf.git",
      "state" : {
        "revision" : "0af9125c4eae12a4973fb66574c53a54962a9e1e",
        "version" : "1.21.0"
      }
    }
  ],
  "version" : 2
}

If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

Replace this line with the contents of your Podfile.lock!

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[SKuhlemann]

Additionally I saw in the logs, that there is always another message relating to "app_measurement" at app start:
MyApp[5322:1643932] 10.6.0 - [FirebaseAnalytics][I-ACS800023] No pending snapshot to activate. SDK name: app_measurement

Attached you find debug logs of a minimal reproducible example:
firebase-log.txt

[rizafran]

Thanks for reporting this, @SKuhlemann. I was able to reproduce the issue using the Analytics Quickstart. Let me consult this to the Analytics team, and I'll let you know once I got an update.

[tsunghung]

Thanks for the issue report.

• We will lower the log level of "[FirebaseAnalytics][I-ACS800014] Cannot get flag for unregistered flag..." to make it less spammy.
• "[FirebaseAnalytics][I-ACS800023] No pending snapshot to activate..." should only appear a few times after app install.

You can safely ignore these messages. They are expected and not harmful.

[SKuhlemann]

Thank you for the information.