Firebase Remote Config provides lots of flexibility for how and when to
fetch new values from the server and activate them in your app, allowing you to
ensure a quality end user experience by controlling the timing of any visible
configuration changes. You can fetch new values on application launch using
fetchAndActivate(), and use
real-time Remote Config
as a complementary method to automatically fetch the latest parameter values
after a new version of your Remote Config is published.
This guide looks at a few loading strategies and discusses key considerations for picking the best option for your app.
Strategy 1: Fetch and activate on load
In this strategy, your app would call fetchAndActivate() when your app first
starts up to fetch new values from Remote Config and activate them as soon
as they are done loading. This simple approach works well for configuration
changes that don't cause
any dramatic visual changes in your UI. It should be
avoided in any situation where your UI could change noticeably
while users are in the middle of using it.
After your app calls fetchAndActivate(), it can start listening for parameter
value updates in real time by calling addOnConfigUpdateListener. This method
starts listening for any server-side updates to parameter values, fetches them
automatically, then calls the listener. A simple strategy is to activate the new
values in the listener. However, as mentioned for fetchAndActivate(),
activating immediately should be avoided for sensitive UIs.
Strategy 2: Activate behind loading screen
As a remedy to the potential UI issue encountered in strategy 1, you could rely
on a loading screen. Instead of starting up your app right away, show a loading
screen and call fetchAndActivate in your completion handler.
Then right after that — again using a callback or a notification
— dismiss the loading screen and allow the user to start interacting with
your app.
If you use this strategy, it's recommended to add a timeout to the loading screen. Remote Config's one-minute timeout may be too long for a quality app startup experience for users.
Listening for real-time Remote Config updates by calling
addOnConfigUpdateListener works well with this strategy. Add the listener when
the loading screen is displayed, then use activate() at one or more points in
your app where Remote Config values won't cause dramatic visual changes.
Strategy 3: Load new values for next startup
An effective strategy is to load new configuration values to activate on your app's next startup. In this strategy, your app activates fetched values on startup before attempting to fetch new ones, operating on the assumption that it may have already fetched — but not yet activated — new configuration values. The order of operations for this strategy is:
- On startup, immediately activate previously fetched values. This applies any values you've downloaded from the server in a previous session, and is nearly instantaneous.
- While the user interacts with your app, kick off an asynchronous call to fetch new values according to the default minimum fetch interval and add a real-time config update listener. The real-time listener will automatically fetch any values that are published on the server while your app is running. Real-time updates bypass the minimum fetch interval setting.
- In the completion handler or callback for the fetch call, do nothing. Your app will keep the downloaded values until you activate them the next time the app starts.
With this strategy, user wait time is greatly minimized. Combining the fetch
and real-time listener strategies with activate() calls as needed in the app lifecycle makes sure users
have the latest values from Remote Config as they interact with your app.
Loading anti-strategies
As you may have understood from the above discussion of loading pros and cons, there are a couple of usage patterns to avoid.
- Don't update or switch aspects of the UI while the user is viewing or interacting with it — unless you have strong app or business reasons for doing so, like removing options related to a promotion that has just ended.
- Don't send mass numbers of simultaneous fetch requests, which could result in the server throttling your app. If you need to fetch updates frequently, use real-time Remote Config. While the risk of throttling is low in most production scenarios, it can be an issue during active development—and real-time Remote Config is designed for this use case. Check out the throttling guidance.
- Don't rely on network connectivity to obtain Remote Config values. Do set in-app default parameter values so that your app always behaves as expected. You can periodically keep app and Remote Config backend default values in sync using downloaded template defaults.
Next steps
These three basic strategies do not by any means comprise a complete list of the ways to load configuration values. Depending on your needs, you could devise much more sophisticated strategies.
Check out the API reference for your platform to learn more about the specific calls for fetching and activating configuration values.