Feature Toggle — 基本、スイッチの種類、応用

const config = require("./config.json");

const toggles = {
    get(name) {
        return config.features[name] ?? false;
    },
    isEnabled(name, context) {
        const toggle = config.features[name];
        if (!toggle) return false;
        if (toggle.enabled === true) return true;
        if (toggle.percentage && context.userId) {
            return hashCode(context.userId) % 100 < toggle.percentage;
        }
        return false;
    }
};

const app = express();

app.use("/api/checkout", (req, res, next) => {
    if (toggles.isEnabled("new_checkout", req)) {
        return newCheckoutHandler(req, res);
    }
    return legacyCheckoutHandler(req, res);
});

package toggles

type Toggle struct {
    Name      string
    Enabled   bool
    Owner     string
    CreatedAt time.Time
    TTL       time.Duration
}

type ToggleManager struct {
    store map[string]*Toggle
}

func NewToggleManager() *ToggleManager {
    return &ToggleManager{store: make(map[string]*Toggle)}
}

func (m *ToggleManager) IsEnabled(name string) bool {
    t, ok := m.store[name]
    if !ok {
        return false
    }
    return t.Enabled
}

func (m *ToggleManager) GetStaleToggles() []string {
    var stale []string
    for name, t := range m.store {
        if t.Enabled && time.Since(t.CreatedAt) > t.TTL {
            stale = append(stale, name)
        }
    }
    return stale
}