✨ Feat : Implements ConcurrentBatchCounter (#34)

## 개요

- 새롭게 정의한 `ConcurrentBatchCounter` 인터페이스에 대한 구현체

## 변경 사항

- [x] ✨ Feat : `ConcurrentBatchingCounter`
- [x] ✨ Feat : `ConcurrentParameterizedBatchingCounter`

## 추가 정보

- 스레드 별 고유 ID로 분리하여 안정성 확보
#### `ConcurrentParameterizedBatchingCounter`
- 임의의 Integer를 받는 식으로 구현
   - 배열의 크기가 커지면 메모리 이슈 발생
   - 내부 기준에 따라 `flush`하여 해결
#### `ConcurrentBatchingCounter`
- YAGNI 원칙에 의거하여 최적의 구현체 고안
   - LongAdder로 연산 속도 개선
#### 테스트
- Virtual Thread와 OS Thread, 그리고 Sync/Async 각각의 방식으로 시도
   - 두 경우 모두 싱글 스레드 동작이 약 4배 빠름 (평균 10초)
   - OS Thread는 Thread 수에 비례하여 생성 오버헤드 증가
   - Virtual Thread는 수와 관계없이 일정 (평균 40초)

### 관련 이슈
Closes #33

Author: ooMia

.github/ISSUE_TEMPLATE/bug_report.md

@@ -12,6 +12,7 @@ A clear and concise description of what the bug is.
 
 **To Reproduce**
 Steps to reproduce the behavior:
+
 1. Go to '...'
 2. Click on '....'
 3. Scroll down to '....'
@@ -24,15 +25,17 @@ A clear and concise description of what you expected to happen.
 If applicable, add screenshots to help explain your problem.
 
 **Desktop (please complete the following information):**
- - OS: [e.g. iOS]
- - Browser [e.g. chrome, safari]
- - Version [e.g. 22]
+
+- OS: [e.g. iOS]
+- Browser [e.g. chrome, safari]
+- Version [e.g. 22]
 
 **Smartphone (please complete the following information):**
- - Device: [e.g. iPhone6]
- - OS: [e.g. iOS8.1]
- - Browser [e.g. stock browser, safari]
- - Version [e.g. 22]
+
+- Device: [e.g. iPhone6]
+- OS: [e.g. iOS8.1]
+- Browser [e.g. stock browser, safari]
+- Version [e.g. 22]
 
 **Additional context**
 Add any other context about the problem here.

src/main/java/com/thread/concurrency/SpringThreadConcurrencyApplication.java

@@ -1,13 +1,81 @@
 package com.thread.concurrency;
 
+import com.thread.concurrency.counter.batch.BatchCounter;
+import com.thread.concurrency.counter.batch.ConcurrentBatchingCounter;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryUsage;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Consumer;
+
 @SpringBootApplication
 public class SpringThreadConcurrencyApplication {
 
     public static void main(String[] args) {
         SpringApplication.run(SpringThreadConcurrencyApplication.class, args);
+
+        MemoryMXBean memoryMXBean = ManagementFactory.getMemoryMXBean();
+        MemoryUsage initialMemoryUsage = memoryMXBean.getHeapMemoryUsage();
+        long initialTime = System.currentTimeMillis();
+
+        // Run the test
+        int totalRequest = Integer.MAX_VALUE;
+        conditionalMultiThreading(totalRequest);
+
+        MemoryUsage finalMemoryUsage = memoryMXBean.getHeapMemoryUsage();
+        long finalTime = System.currentTimeMillis();
+        long elapsedTime = finalTime - initialTime;
+        long usedMemory = finalMemoryUsage.getUsed() - initialMemoryUsage.getUsed();
+
+        // request with comma
+        System.out.println("Total request: " + String.format("%,d", totalRequest));
+        // seconds
+        System.out.println("Elapsed time: " + elapsedTime / 1000 + " s");
+        // megabytes
+        System.out.println("Used memory: " + usedMemory / 1024 / 1024 + " MB");
+    }
+
+    private static void conditionalMultiThreading(int expected) {
+        BatchCounter counter = new ConcurrentBatchingCounter();
+
+        // given
+        int numberOfThreads = 128;
+        List<Integer> iterPerThread = range(numberOfThreads, expected);
+        Consumer<Integer> task = (Integer number) -> {
+            for (int i = 0; i < number; i++) {
+                counter.add(1);
+            }
+            counter.flush();
+        };
+        // when
+        try (ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor()) {
+            List<CompletableFuture<Void>> futures = iterPerThread.stream().map(number -> CompletableFuture.runAsync(() -> task.accept(number), executor)).toList();
+            futures.forEach(CompletableFuture::join);
+        }
+        // then
+        assert expected == counter.show();
+    }
+
+    private static List<Integer> range(int numberOfThreads, int expected) {
+        int baseValue = expected / numberOfThreads;
+        int remainder = expected % numberOfThreads;
+
+        List<Integer> result = new ArrayList<>();
+        for (int i = 0; i < numberOfThreads; i++) {
+            if (i < remainder) {
+                result.add(baseValue + 1);
+            } else {
+                result.add(baseValue);
+            }
+        }
+        return result;
     }
 
 }

src/main/java/com/thread/concurrency/counter/BatchingCounter.java

@@ -0,0 +1,7 @@
+package com.thread.concurrency.counter.batch;
+
+import com.thread.concurrency.counter.Counter;
+
+public interface BatchCounter extends Counter {
+    void flush();
+}

src/main/java/com/thread/concurrency/counter/batch/BatchCounter.java

@@ -0,0 +1,39 @@
+package com.thread.concurrency.counter.batch;
+
+import org.springframework.stereotype.Component;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.LongAdder;
+
+@Component
+public class ConcurrentBatchingCounter implements BatchCounter {
+
+    private final AtomicLong counter = new AtomicLong();
+    private final ConcurrentMap<Long, LongAdder> batch = new ConcurrentHashMap<>();
+
+    @Override
+    public void add(int value) {
+        var threadId = Thread.currentThread().threadId();
+        batch.computeIfAbsent(threadId, k -> new LongAdder()).add(value);
+    }
+
+    @Override
+    public int show() {
+        return counter.intValue();
+    }
+
+    private void flush(long threadId) {
+        var value = batch.remove(threadId);
+        if (value != null) {
+            counter.addAndGet(value.longValue());
+        }
+    }
+
+    @Override
+    public void flush() {
+        var threadId = Thread.currentThread().threadId();
+        flush(threadId);
+    }
+}

src/main/java/com/thread/concurrency/counter/batch/ConcurrentBatchingCounter.java

@@ -0,0 +1,48 @@
+package com.thread.concurrency.counter.batch;
+
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Component;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+@Component
+@Profile("dev")
+public class ConcurrentParameterizedBatchingCounter implements BatchCounter {
+
+    private static final int BATCH_SIZE = 100;
+
+    private final AtomicLong counter = new AtomicLong();
+    private final ConcurrentMap<Long, List<Integer>> batch = new ConcurrentHashMap<>();
+
+    @Override
+    public void add(int value) {
+        var threadId = Thread.currentThread().threadId();
+        batch.computeIfAbsent(threadId, k -> new ArrayList<>()).add(value);
+        if (batch.get(threadId).size() >= BATCH_SIZE) {
+            flush(threadId);
+        }
+    }
+
+    @Override
+    public int show() {
+        return counter.intValue();
+    }
+
+    private void flush(long threadId) {
+        var list = batch.getOrDefault(threadId, null);
+        if (list != null && !list.isEmpty()) {
+            counter.addAndGet(list.stream().mapToLong(Integer::longValue).sum());
+            batch.remove(threadId);
+        }
+    }
+
+    @Override
+    public void flush() {
+        var threadId = Thread.currentThread().threadId();
+        flush(threadId);
+    }
+}

src/main/java/com/thread/concurrency/counter/batch/ConcurrentParameterizedBatchingCounter.java

@@ -1 +1,2 @@
 spring.application.name=spring-thread-concurrency
+spring.profiles.active=default

src/main/resources/application.properties

@@ -5,60 +5,44 @@
 import org.junit.jupiter.params.provider.MethodSource;
 import org.springframework.boot.test.context.SpringBootTest;
 
-import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.stream.Stream;
 
-import static java.lang.Thread.sleep;
-
 @SpringBootTest
 public class CounterTest {
 
     public static Stream<Counter> counterProvider() {
-        return Stream.of(new BatchingCounter(), new LockCounter(), new PollingCounter(), new BasicCounter());
+        return Stream.of(new LockCounter(), new PollingCounter());
     }
 
-    private static void assertThen(Counter counter, int expectedValue, int actualValue) {
-        System.out.println("Expected value: " + expectedValue);
-        System.out.println("Actual value: " + actualValue);
-        if (counter instanceof BasicCounter) {
-            System.out.println("BasicCounter is not thread-safe");
-            Assertions.assertNotEquals(expectedValue, actualValue);
-        } else {
-            System.out.println("Counter is thread-safe");
-            Assertions.assertEquals(expectedValue, actualValue);
+    private static void whenAdd(Counter counter, int nThreads, int addPerThread) {
+        try (ExecutorService executor = Executors.newFixedThreadPool(nThreads)) {
+            for (int i = 0; i < nThreads; i++) {
+                executor.submit(() -> {
+                    for (int j = 0; j < addPerThread; j++) {
+                        counter.add(1);
+                    }
+                });
+            }
         }
     }
 
     @ParameterizedTest
     @MethodSource("counterProvider")
-    public void stressTest(Counter counter) throws InterruptedException {
-        int initialValue = counter.show();
+    public void stressTest(Counter counter) {
+        // given
         int nThreads = 100;
-        int nAddsPerThread = 1000;
-        int valueToAdd = 1;
-        int expectedValue = initialValue + nThreads * nAddsPerThread * valueToAdd;
-
-
-        // define runnable job
-        CountDownLatch latch = new CountDownLatch(nThreads);
-        Runnable job = () -> {
-            try {
-                latch.countDown(); // decrease the count
-                latch.await(); // wait until the count reaches 0
-                for (int i = 0; i < nAddsPerThread; i++) {
-                    counter.add(valueToAdd);
-                }
-            } catch (InterruptedException ignored) {
-            }
-        };
-
-        // start nThreads threads
-        for (int i = 0; i < nThreads; i++) {
-            Thread.ofVirtual().start(job);
-        }
+        int addPerThread = 1000;
+        int expectedValue = counter.show() + nThreads * addPerThread;
 
-        sleep(300); // wait for all threads to finish
+        // when
+        long start = System.currentTimeMillis();
+        whenAdd(counter, nThreads, addPerThread);
+        long end = System.currentTimeMillis();
 
-        assertThen(counter, expectedValue, counter.show());
+        // then
+        Assertions.assertEquals(expectedValue, counter.show());
+        System.out.println("Time elapsed: " + (end - start) + "ms");
     }
 }

src/test/java/com/thread/concurrency/counter/CounterTest.java

@@ -1,15 +1,15 @@
-package com.thread.concurrency;
+package com.thread.concurrency.counter;
 
+import com.thread.concurrency.SpringThreadConcurrencyApplication;
 import org.junit.jupiter.api.Test;
 import org.springframework.boot.test.context.SpringBootTest;
+
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 @SpringBootTest
 class SpringThreadConcurrencyApplicationTests {
-
     @Test
     void contextLoads() {
         assertDoesNotThrow(() -> SpringThreadConcurrencyApplication.main(new String[]{}));
     }
-
 }