Intermediate changes

Author: robot-piglet

yt/yt/core/misc/fair_scheduler-inl.h

@@ -34,12 +34,14 @@ class TFairScheduler
         bucket->Tasks.push(std::move(task));
     }
 
-    TTask Dequeue() override
+    std::optional<TTask> TryDequeue() override
     {
         auto guard = Guard(Lock_);
 
         while (true) {
-            YT_VERIFY(!BucketHeap_.empty());
+            if (BucketHeap_.empty()) {
+                return std::nullopt;
+            }
 
             auto* bucket = BucketHeap_.front();
             YT_ASSERT(bucket->InHeap);
@@ -77,13 +79,6 @@ class TFairScheduler
         YT_ABORT();
     }
 
-    bool IsEmpty() const override
-    {
-        auto guard = Guard(Lock_);
-
-        return BucketHeap_.empty();
-    }
-
     void ChargeUser(const std::string& user, TDuration time) override
     {
         auto guard = Guard(Lock_);

yt/yt/core/misc/fair_scheduler.h

@@ -11,9 +11,7 @@ struct IFairScheduler
     : public TRefCounted
 {
     virtual void Enqueue(TTask task, const std::string& user) = 0;
-    virtual TTask Dequeue() = 0;
-
-    virtual bool IsEmpty() const = 0;
+    virtual std::optional<TTask> TryDequeue() = 0;
 
     virtual void ChargeUser(const std::string& user, TDuration time) = 0;
 };

yt/yt/core/misc/unittests/fair_scheduler_ut.cpp

@@ -13,19 +13,17 @@ class TFairSchedulerTest
     : public ::testing::Test
 {
 protected:
-    IFairSchedulerPtr<TString> Scheduler_ = CreateFairScheduler<TString>();
+    const IFairSchedulerPtr<TString> Scheduler_ = CreateFairScheduler<TString>();
 };
 
 TEST_F(TFairSchedulerTest, Simple)
 {
     Scheduler_->Enqueue("T1", "John");
     Scheduler_->Enqueue("T2", "John");
 
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "T1");
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "T2");
-    EXPECT_TRUE(Scheduler_->IsEmpty());
+    EXPECT_EQ(Scheduler_->TryDequeue(), "T1");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "T2");
+    EXPECT_EQ(Scheduler_->TryDequeue(), std::nullopt);
 }
 
 TEST_F(TFairSchedulerTest, Fairness1)
@@ -36,19 +34,15 @@ TEST_F(TFairSchedulerTest, Fairness1)
     Scheduler_->Enqueue("B1", "Bob");
     Scheduler_->Enqueue("B2", "Bob");
 
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "A1");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "A1");
     Scheduler_->ChargeUser("Alice", TDuration::Seconds(2));
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "B1");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "B1");
     Scheduler_->ChargeUser("Bob", TDuration::Seconds(2));
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "A2");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "A2");
     Scheduler_->ChargeUser("Alice", TDuration::Seconds(2));
-    EXPECT_FALSE(Scheduler_->IsEmpty());
-    EXPECT_EQ(Scheduler_->Dequeue(), "B2");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "B2");
     Scheduler_->ChargeUser("Bob", TDuration::Seconds(2));
-    EXPECT_TRUE(Scheduler_->IsEmpty());
+    EXPECT_EQ(Scheduler_->TryDequeue(), std::nullopt);
 }
 
 TEST_F(TFairSchedulerTest, Fairness2)
@@ -59,16 +53,16 @@ TEST_F(TFairSchedulerTest, Fairness2)
         Scheduler_->Enqueue(Format("B%v", index), "Bob");
     }
 
-    EXPECT_EQ(Scheduler_->Dequeue(), "A1");
+    EXPECT_EQ(Scheduler_->TryDequeue(), "A1");
     Scheduler_->ChargeUser("Alice", TDuration::Seconds(100500));
 
     for (int index = 1; index <= 10; ++index) {
-        EXPECT_EQ(Scheduler_->Dequeue(), Format("B%v", index));
+        EXPECT_EQ(Scheduler_->TryDequeue(), Format("B%v", index));
         Scheduler_->ChargeUser("Bob", TDuration::Seconds(1));
     }
 
     for (int index = 2; index <= 10; ++index) {
-        EXPECT_EQ(Scheduler_->Dequeue(), Format("A%v", index));
+        EXPECT_EQ(Scheduler_->TryDequeue(), Format("A%v", index));
     }
 }