Add logging for Adaptive Concurrency Controller configuration event (…

…2/2)

Summary: Adds the ability to set a callback on the AdaptiveConcurrencyController that fires when the internal Config changes (e.g. via a Configerator update). ThriftServer utilizes this callback mechanism to log a new THRIFT_SERVER_EVENT (ACC_enabled) if the AdaptiveConcurrencyController has been enabled by the Config change.

Reviewed By: ycking21

Differential Revision: D35603212

fbshipit-source-id: 3b411b79a83545d9d5c5eea53ad4218465ba7dec

thrift/lib/cpp2/server/AdaptiveConcurrency.cpp

@@ -52,6 +52,9 @@ AdaptiveConcurrencyController::AdaptiveConcurrencyController(
       concurrencyLimit_(config().minConcurrency) {
   rttRecalcStart_ = config().isEnabled() ? Clock::now() : kZero;
   enablingCallback_ = config_.addCallback([this](auto snapshot) {
+    if (this->configUpdateCallback_) {
+      this->configUpdateCallback_(snapshot);
+    }
     rttRecalcStart_ = snapshot->isEnabled() ? Clock::now() : kZero;
     // reset all the state
     maxRequests_.store(0, std::memory_order_relaxed);
@@ -222,5 +225,11 @@ size_t AdaptiveConcurrencyController::getConcurrency() const {
   return concurrencyLimit_.load(std::memory_order_relaxed);
 }
 
+void AdaptiveConcurrencyController::setConfigUpdateCallback(
+    std::function<void(folly::observer::Snapshot<Config>)> callback) {
+  callback(*config_);
+  configUpdateCallback_ = std::move(callback);
+}
+
 } // namespace thrift
 } // namespace apache

thrift/lib/cpp2/server/AdaptiveConcurrency.h

@@ -119,6 +119,9 @@ class AdaptiveConcurrencyController {
   // to minConcurrency when controller is in the rtt calibration state.
   size_t getConcurrency() const;
 
+  void setConfigUpdateCallback(
+      std::function<void(folly::observer::Snapshot<Config>)> callback);
+
  private:
   // testing helpers
   friend class AdaptiveConcurrencyTestHelper;
@@ -148,6 +151,7 @@ class AdaptiveConcurrencyController {
   folly::observer::Observer<Config> config_;
   folly::observer::Observer<uint32_t> maxRequestsLimit_;
   folly::observer::CallbackHandle enablingCallback_;
+  std::function<void(folly::observer::Snapshot<Config>)> configUpdateCallback_;
 
   std::atomic<Duration> targetRtt_{Duration{}};
   std::atomic<Duration> minRtt_{Duration{}};

thrift/lib/cpp2/server/ThriftServer.cpp

@@ -224,6 +224,12 @@ ThriftServer::ThriftServer()
   setMonitoringInterface(std::move(extraInterfaces.monitoring));
   setStatusInterface(std::move(extraInterfaces.status));
   setControlInterface(std::move(extraInterfaces.control));
+  getAdaptiveConcurrencyController().setConfigUpdateCallback(
+      [this](auto snapshot) {
+        if (snapshot->isEnabled()) {
+          THRIFT_SERVER_EVENT(ACC_enabled).log(*this);
+        }
+      });
 }
 
 ThriftServer::ThriftServer(