Unleash Android SDK is not sending mandatory appName for frontend metrics

[andreaobitz]

Describe the bug

When integrating the Unleash Android SDK into an Android (Kotlin) project, the SDK automatically sends HTTP POST requests to the /client/metrics endpoint. These requests include the header:

Content-Type: application/json;charset=utf-8

This header is set internally by the SDK and includes the charset=utf-8 parameter by default. I couldn't find any configuration option in the SDK to modify or remove the charset=utf-8 part from the Content-Type header.

Steps to reproduce the bug

1. Add the Unleash Android SDK to an Android project
2. Run the app and observe network traffic via a proxy tool such as Proxyman
3. Notice POST requests to /client/metrics with header Content-Type: application/json;charset=utf-8
4. Attempt to find SDK configuration to change this header — none available

Expected behavior

It should be possible to customize or remove the charset=utf-8 parameter from the Content-Type header in the metrics requests, as some backend servers or proxies may reject or mishandle this header

Logs, error output, etc.

Screenshots

Additional context

Unleash Android SDK version: io.getunleash:unleash-android version 2.0.1
Android Studio version:
Android Studio Meerkat Feature Drop | 2024.3.2
Build #AI-243.25659.59.2432.13423653, built on April 29, 2025
Runtime version: 21.0.6+-13368085-b895.109 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.awt.windows.WToolkit
Windows 11.0
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 2048M
Cores: 28
Registry:
ide.experimental.ui=true
io.getunleash:unleash-android
Android device: Motorola moto g34 5G, Android 15
Network proxy tool: Proxyman

Unleash version

2.0.1

Subscription type

None

Hosting type

None

SDK information (language and version)

No response

[gastonfournier]

Hi @andreaobitz this is indeed unexpected. We'll check it out

[gastonfournier]

@andreaobitz looking at it again, should it be a problem of Android? I think utf-8 in the header is not the problem and actually edge (which seems to be what you're integrating against) should be able to handle this header...

[gastonfournier]

Ok, it does seem to be a problem with the SDK (either Android or Java), but it's not due to the charset=utf-8.

The problem is the one stated in the response body: appName is missing in the body and it seems to be mandatory for frontend APIs.

I checked running Unleash and edge locally and they both accept ; charset=utf-8, but both fails when the appName is removed from the payload:

$ curl -w "%{http_code}"  -X POST -H'Content-Type: application/json;charset=utf-8' -H'Authorization: *:development.unleash-insecure-frontend-api-token' localhost:3063/api/frontend/client/metrics -d '{
  "platformName": "curl",
  "platformVersion": "1",
  "sdkVersion": "0.0.1",
  "yggdrasilVersion": "0.0.5",
  "appName": "mycurl",
  "bucket": {
    "start": "2025-05-28T14:15:22Z",
    "stop": "2025-05-28T14:20:22Z",
    "toggles": {
      "property1": {
        "no": 1,
        "variants": {
          "property1": 1,
          "property2": 1
        },
        "yes": 2
      },
      "property2": {
        "no": 5,
        "variants": {
          "property1": 2,
          "property2": 3
        },
        "yes": 0
      }
    }
  },
  "connectionId": "xyz",
  "environment": "development",
  "instanceId": "my-instance"
}'
202 

While removing the appName property would result in:

Json deserialize error: missing field `appName` at line 31 column 1400

[gastonfournier]

I ran the sample app and it's sending metrics properly, would you mind checking the body of your request? Please, reopen if you find more details about it

This is what I got when running it through a proxy with (application/json;charset=utf-8 header):

[andreaobitz]

@gastonfournier

The problem is the one stated in the response body: appName is missing in the body and it seems to be mandatory for frontend APIs.

I checked again and even when there is appName in the body I am still getting error 400:

removing charset=utf-8 from content-type solves my problem 🤔

PS. I cannot reopen this issue as I don't have necessary permissions

[gastonfournier]

Hi, @andreaobitz is there a specific version of edge you're using? I tested the latest and it works fine. Also, could it be something else? Maybe you're using a custom http client or perhaps it's something in the network layer (ingress controller or something). Edge should not be failing and Android SDK accepts the charset utf-8... I tested using: https://github.com/Unleash/unleash-android/blob/main/app/src/main/java/io/getunleash/unleashandroid/MainActivity.kt can you try to reproduce it there?

Also, can you copy the request as a curl statement? You can remove host and other details