Join Custom Audience Delegation

The fetchAndJoinCustomAudience API allows buyers to delegate joining a custom audience by leveraging the on-device presence of their partner MMPs or SSPs.

Overview

A general overview of how this works is that the on-device caller (whether that be an MMP or an SSP SDK) creates a fetchAndJoinCustomAudienceRequest that looks like the following:

Kotlin

/**
 * @param fetchUri The URL to retrieve the CA from.
 * (optional)@param name The name of the CA to join.
 * (optional)@param activationTime The time when the CA will activate.
 * (optional)@param expirationTime The time when the CA will expire,
    must be a time in the future otherwise this will fail
 * (optional)@param userBiddingSignals The user bidding signals used at auction.
*/

val request = FetchAndJoinCustomAudienceRequest.Builder(fetchUri)
    .setName(name)
    .setActivationTime(activationTime)
    .setExpirationTime(expirationTime)
    .setUserBiddingSignals(userBiddingSignals)
    .build()

Java

/**
 * @param fetchUri The URL to retrieve the CA from.
 * (optional)@param name The name of the CA to join.
 * (optional)@param activationTime The time when the CA will activate.
 * (optional)@param expirationTime The time when the CA will expire,
    must be a time in the future otherwise this will fail
 * (optional)@param userBiddingSignals The user bidding signals used at auction.
*/

FetchAndJoinCustomAudienceRequest request =
 new FetchAndJoinCustomAudienceRequest.Builder(fetchUri)
  .setName(name) //Optional
  .setActivationTime(activationTime) //Optional
  .setExpirationTime(expirationTime) //Optional
  .setUserBiddingSignals(userBiddingSignals) //Optional
  .build();

An important note about all of the optional parameters is that if they are set inside of the fetch request, their data cannot be overridden by what is returned from the Buyer, giving the on-device caller additional controls over what custom audience is persisted.

The fetchUri should point to a server endpoint operated by the Buyer which will return a Custom Audience JSON object that matches the format seen here:

//Return a 200 response with data matching the format of the following in the body
{
  "daily_update_uri": "https://js.example.com/bidding/daily",
  "bidding_logic_uri": "https://js.example.com/bidding",
  "user_bidding_signals": {
    "valid": true,
    "arbitrary": "yes"
  },
  "trusted_bidding_data": {
    "trusted_bidding_uri": "https://js.example.com/bidding/trusted",
    "trusted_bidding_keys": [
      "key1",
      "key2"
    ]
  },
  "ads": [
    {
      "render_uri": "https://js.example.com/render/fetch_and_join_ad1",
      "metadata": {
        "valid": 1
      }
    },
    {
      "render_uri": "https://js.example.com/render/fetch_and_join_ad2",
      "metadata": {
        "valid": 2
      }
    }
  ]
}

Further information about how this resolves on the API side can be found in the Design Proposal for Join CA Delegation.

Testing

Once you've implemented the Fetch call inside of the client code and have an endpoint set up on the DSP side to return the Custom Audience Data, you can test delegation of joining a Custom Audience. Before running your app, you will need to run the following command to open up the UI to enable the Privacy Sandbox:

adb shell am start -n com.google.android.adservices.api/com.android.adservices.ui.settings.activities.AdServicesSettingsMainActivity

Once the UI pops up, make sure that you toggle to enable the Privacy Sandbox, then run the following ADB commands to finish setting up the device for testing:

adb shell device_config set_sync_disabled_for_tests persistent
adb shell device_config put adservices ppapi_app_signature_allow_list \"\*\"
adb shell device_config put adservices ppapi_app_allow_list \"\*\"
adb shell device_config put adservices adservice_system_service_enabled true
adb shell device_config put adservices adservice_enabled true
adb shell device_config put adservices adservice_enable_status true
adb shell device_config put adservices global_kill_switch false
adb shell device_config put adservices fledge_js_isolate_enforce_max_heap_size false
adb shell device_config put adservices fledge_custom_audience_service_kill_switch false
adb shell device_config put adservices fledge_select_ads_kill_switch false
adb shell device_config put adservices adid_kill_switch false
adb shell setprop debug.adservices.disable_fledge_enrollment_check true
adb shell device_config put adservices fledge_fetch_custom_audience_enabled true

Once you've run these commands, you should be able to start successfully making calls using the Fetch API.

To see an example of this flow, fetch calls have been added to the developer preview branch of the Privacy Sandbox Samples repository on Github.