Only observe lag on tasks with Thrift's folly::RequestContext attached to it.

Reviewed By: andriigrynenko

Differential Revision: D25814958

fbshipit-source-id: abc2448bf93c5016411629936a8c7f06bb0033e6

folly/concurrency/QueueObserver.h

@@ -24,11 +24,13 @@
 
 namespace folly {
 
+class RequestContext;
+
 class QueueObserver {
  public:
   virtual ~QueueObserver() {}
 
-  virtual intptr_t onEnqueued() = 0;
+  virtual intptr_t onEnqueued(const RequestContext*) = 0;
   virtual void onDequeued(intptr_t) = 0;
 };
 

folly/executors/CPUThreadPoolExecutor.cpp

@@ -170,7 +170,8 @@ void CPUThreadPoolExecutor::add(
     Func expireCallback) {
   CPUTask task{std::move(func), expiration, std::move(expireCallback), 0};
   if (auto queueObserver = getQueueObserver(0)) {
-    task.queueObserverPayload() = queueObserver->onEnqueued();
+    task.queueObserverPayload() =
+        queueObserver->onEnqueued(task.context_.get());
   }
   auto result = taskQueue_->add(std::move(task));
   if (!result.reusedThread) {
@@ -191,7 +192,8 @@ void CPUThreadPoolExecutor::add(
   CPUTask task(
       std::move(func), expiration, std::move(expireCallback), priority);
   if (auto queueObserver = getQueueObserver(priority)) {
-    task.queueObserverPayload() = queueObserver->onEnqueued();
+    task.queueObserverPayload() =
+        queueObserver->onEnqueued(task.context_.get());
   }
   auto result = taskQueue_->addWithPriority(std::move(task), priority);
   if (!result.reusedThread) {