Add mcrouter runtime features for ODSL

Summary: Support to dynamically turn on/off features via routing config. Used initially for ODSL feature.

Reviewed By: djvaporize

Differential Revision: D53374529

fbshipit-source-id: c927a3e2a67382477ca60d83823ae2644d62df76

mcrouter/CarbonRouterInstanceBase.h

@@ -243,6 +243,16 @@ class CarbonRouterInstanceBase {
     axonProxyClientFactory_ = std::move(clientFactory);
   }
 
+  /**
+   * Runtime features that can be enabled from runtime_features block
+   * in routing config
+   */
+  struct RuntimeFeatures {
+    std::atomic<bool> enableOdslScuba = false;
+    std::atomic<bool> enableOdslODS = false;
+  };
+  RuntimeFeatures runtimeFeatures_;
+
  protected:
   void resetMetadata() {
     metadata_.reset();

mcrouter/ProxyConfig-inl.h

@@ -128,6 +128,11 @@ ProxyConfig<RouterInfo>::ProxyConfig(
 
   bool enableAsyncDlBroadcast = readBool("enable_async_dl_broadcast", false);
 
+  proxy.router().runtimeFeatures_.enableOdslScuba =
+      readBool("enable_odsl_scuba", false);
+  proxy.router().runtimeFeatures_.enableOdslODS =
+      readBool("enable_odsl_ods", false);
+
   proxyRoute_ = std::make_shared<ProxyRoute<RouterInfo>>(
       proxy,
       routeSelectors,