Spring Boot 微服务中的 Feature Toggle 实战：OpenFeature Property Provider + K8s ConfigMap 热更新

@ConfigurationProperties(prefix = "shop.features")
public class FeatureToggleProperties {

    private Map<String, Boolean> flags = new LinkedHashMap<>();

    public Map<String, Boolean> getFlags() { return flags; }
    public void setFlags(Map<String, Boolean> flags) {
        this.flags = flags == null ? new LinkedHashMap<>() : new LinkedHashMap<>(flags);
    }
    public boolean contains(String key) { return flags.containsKey(key); }
    public Boolean get(String key) { return flags.get(key); }
}

public class OpenFeaturePropertyProvider implements FeatureProvider {

    private static final Metadata METADATA = () -> "shop-k8s-property-provider";

    private final FeatureToggleProperties properties;

    @Override
    public Metadata getMetadata() { return METADATA; }

    @Override
    public ProviderEvaluation<Boolean> getBooleanEvaluation(
            String key, Boolean defaultValue, EvaluationContext context) {
        if (!properties.contains(key)) {
            return missing(key, defaultValue);
        }
        Boolean value = properties.get(key);
        return ProviderEvaluation.<Boolean>builder()
                .value(value)
                .variant(Boolean.TRUE.equals(value) ? "enabled" : "disabled")
                .reason("STATIC")
                .flagMetadata(ImmutableMetadata.builder()
                        .addString("source", "spring-config")
                        .addString("key", key)
                        .build())
                .build();
    }

    @Override
    public ProviderEvaluation<String> getStringEvaluation(...) {
        return typeMismatch(key, defaultValue);
    }
    // ... getIntegerEvaluation / getDoubleEvaluation / getObjectEvaluation
}

@AutoConfiguration
@EnableConfigurationProperties(FeatureToggleProperties.class)
public class FeatureToggleAutoConfiguration {

    static final String OPENFEATURE_DOMAIN = "shop-platform";

    @Bean
    OpenFeaturePropertyProvider openFeaturePropertyProvider(FeatureToggleProperties properties) {
        return new OpenFeaturePropertyProvider(properties);
    }

    @Bean
    Client featureToggleClient(OpenFeaturePropertyProvider provider) {
        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
        api.setProvider(OPENFEATURE_DOMAIN, provider);
        return api.getClient(OPENFEATURE_DOMAIN);
    }

    @Bean
    FeatureToggleService featureToggleService(Client client) {
        return new FeatureToggleService(client);
    }

    @Bean
    DisposableBean openFeatureShutdownHook() {
        return () -> OpenFeatureAPI.getInstance().shutdown();
    }
}

public class FeatureToggleService {

    private final Client client;

    public FeatureToggleService(Client client) {
        this.client = client;
    }

    public boolean isEnabled(String flagKey, boolean defaultValue) {
        return client.getBooleanValue(flagKey, defaultValue);
    }

    public void requireEnabled(String flagKey, boolean defaultValue, String message) {
        if (!isEnabled(flagKey, defaultValue)) {
            throw new BusinessException(CommonErrorCode.FEATURE_DISABLED, message);
        }
    }
}

public final class SearchFeatureFlags {

    public static final String AUTOCOMPLETE = "search-autocomplete";
    public static final String TRENDING = "search-trending";
    public static final String LOCALE_AWARE_SEARCH = "search-locale-aware";

    private SearchFeatureFlags() {}
}

@GetMapping(SearchApi.SEARCH_PRODUCT_SUGGESTIONS)
public ApiResponse<SearchApi.SearchSuggestionsResponse> suggestProducts(
        @RequestParam String q,
        @RequestParam(defaultValue = "8") int limit,
        @RequestParam(required = false) List<String> locales) {
    featureToggleService.requireEnabled(
            SearchFeatureFlags.AUTOCOMPLETE,
            true,
            "Search autocomplete is disabled");
    return ApiResponse.success(searchService.suggest(q, limit, locales));
}

@GetMapping(SearchApi.TRENDING_QUERIES)
public ApiResponse<SearchApi.TrendingQueriesResponse> trendingQueries(
        @RequestParam(defaultValue = "10") int limit) {
    featureToggleService.requireEnabled(
            SearchFeatureFlags.TRENDING,
            true,
            "Trending search queries are disabled");
    return ApiResponse.success(searchService.trending(limit));
}

@GetMapping(SearchApi.SEARCH_PRODUCTS)
public ApiResponse<SearchApi.SearchProductsResponse> searchProducts(
        @RequestParam(required = false) String q,
        @RequestParam(required = false) String categoryId,
        @RequestParam(required = false) String sort,
        @RequestParam(defaultValue = "1") int page,
        @RequestParam(defaultValue = "20") int hitsPerPage,
        @RequestParam(required = false) List<String> locales) {
    List<String> effectiveLocales = locales;
    if (locales != null && !locales.isEmpty()
            && !featureToggleService.isEnabled(
                    SearchFeatureFlags.LOCALE_AWARE_SEARCH, true)) {
        effectiveLocales = List.of();
    }
    var request = new SearchApi.SearchProductsRequest(
            q, categoryId, sort, page, hitsPerPage, effectiveLocales);
    return ApiResponse.success(searchService.search(request));
}

apiVersion: v1
kind: ConfigMap
metadata:
  name: search-service-feature-toggles
  namespace: shop
  labels:
    spring.cloud.kubernetes.config: "true"
  annotations:
    spring.cloud.kubernetes.configmap.apps: search-service
data:
  feature-toggles.yaml: |
    shop:
      features:
        flags:
          search-autocomplete: true
          search-trending: true
          search-locale-aware: true    

spec:
  containers:
    - name: search-service
      volumeMounts:
        - name: search-feature-toggles
          mountPath: /workspace/config/feature-toggles
          readOnly: true
  volumes:
    - name: search-feature-toggles
      configMap:
        name: search-service-feature-toggles

# 只需替换 Provider 实现，大部分业务代码不动
@Bean
Client flagdClient() {
    OpenFeatureAPI api = OpenFeatureAPI.getInstance();
    api.setProvider(new FlagdProvider());  // 替代 OpenFeaturePropertyProvider
    return api.getClient();
}

// 业务调用面通常不变，主要替换 Provider
api.setProvider(new UnleashProvider(unleashConfig));
// 或
api.setProvider(new LaunchDarklyProvider(ldClient));

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: configmap-reader
  namespace: shop
rules:
  - apiGroups: [""]
    resources: ["configmaps"]
    verbs: ["get", "list", "watch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: configmap-reader-binding
  namespace: shop
subjects:
  - kind: ServiceAccount
    name: search-service
    namespace: shop
roleRef:
  kind: Role
  name: configmap-reader
  apiGroup: rbac.authorization.k8s.io