Feature flags - decentraland/unity-explorer GitHub Wiki

The client fetches the information configured at https://features.decentraland.systems/ This process occurs at the start of the application, before the plugins are initialized, so we ensure that we get the data as soon as possible.

We make a call IFeatureFlagsProvider.GetAsync(options, ct). This finally triggers an http request like:

curl --location 'https://feature-flags.decentraland.org/explorer.json' \
--header 'X-Address-Hash: 0x..usrAddr' \
--header 'X-Debug: false' \
--header 'referer: https://decentraland.org' \

We require to set the FeatureFlagOptions options param:

• UserId: the user that is requesting the data. This is required by flags configured with strategy https://gh.getunleash.io/reference/activation-strategies#userids
• URL: decentraland systems uses either https://feature-flags.decentraland.org or https://feature-flags.decentraland.zone
• AppName: refers to the application concept: https://docs.getunleash.io/reference/applications. explorer is set by default
• Hostname: Applies for application hostname strategy: https://gh.getunleash.io/reference/activation-strategies#hostnames. ie: decentraland.org, decentraland.zone, localhost

--feature-flags-url: represents the options.URL param to use different servers.

--feature-flags-hostname: represents the options.Hostname param as it is required to provide the configuration either for org, zone or local development.

An example if you want to set local development mode:

#!/bin/bash
./Decentraland.app --feature-flags-url https://feature-flags.decentraland.zone --feature-flags-hostname localhost

Another example if you want to set it on zone (dev):

#!/bin/bash
./Decentraland.app --feature-flags-url https://feature-flags.decentraland.zone --feature-flags-hostname https://decentraland.zone

The flag names in https://features.decentraland.systems/ should use the explorer-alfa prefix, e.g., explorer-alfa-your-feature. This convention helps differentiate feature flags from the old client.

When received by the client, the explorer prefix will be removed, and feature flags will follow the format alfa-your-feature.

In the codebase, we should also name these flags using the alfa prefix, e.g., alfa-your-feature.

The feature flag configuration is set into FeatureFlagsCache.

private readonly FeatureFlagsCache featureFlagsCache;

public MyClass(FeatureFlagsCache featureFlagsCache)
{
    this.featureFlagsCache = featureFlagsCache;
}

public void DoStuff()
{
    if (!featureFlagsCache.Configuration.IsEnabled("any-feature")) return;
    // Do your feature stuff
}

Refer to: https://gh.getunleash.io/reference/strategy-variants#what-are-strategy-variants

This is how you check if the variant is enabled:

if (!featureFlagsCache.Configuration.IsEnabled("any-feature", "my-variant")) return;

You can get the content in three different formats depending on how its configured: string, json or csv.

private readonly FeatureFlagsCache featureFlagsCache;

public MyClass(FeatureFlagsCache featureFlagsCache)
{
    this.featureFlagsCache = featureFlagsCache;
}

public void DoStringStuff()
{
    if (!featureFlagsCache.Configuration.IsEnabled("any-feature", "string-variant")) return;
    if (!featureFlagsCache.Configuration..TryGetTextPayload("any-feature", "string-variant", out string? str))

    // Do your feature stuff
}

public void DoCsvStuff()
{
    if (!featureFlagsCache.Configuration.IsEnabled("any-feature", "csv-variant")) return;
    if (!featureFlagsCache.Configuration.TryGetCsvPayload("user-allow-list", "csv-variant", out List<List<string>>? csv)) return;
    
    foreach (string value in csv[0])
    {
        // ...
    }
}

[Serializable]
struct MyJsonDto
{
    public string foo;
    public int bar;
}

public void DoJsonStuff()
{
    if (!featureFlagsCache.Configuration.IsEnabled("any-feature", "json-variant")) return;
    if (!featureFlagsCache.Configuration.TryGetCsvPayload("user-allow-list", "json-variant", out MyJsonDto? json)) return;
    
    // Do your feature stuff
}

The FF alfa-temporal-loading-screen-tip has a main variant that allows to enable/disable some loading screens based on the current date/time. A configuration example could be the following:

{
    "displayed": [
        {
            "name": "Summer Sale",
            "startDate": "2024-06-01",
            "endDate": "2024-08-31"
        },
        {
            "name": "Help Center"
        },
        {
            "name": "Holiday Special",
            "startDate": "2024-12-01",
            "endDate": "2024-12-25T12:34"
        }
    ]
}

Notice that:

1. not specifying the dates means "always active"
2. dates only are valid (time will be 00:00:00)
3. dates with time are also valid
4. dates must be in ISO format and expressed in UTC
5. both date bounds must be specified or the config won't be temporal