Stresser

Stresser.java

import static java.util.concurrent.TimeUnit.SECONDS;

import java.time.LocalTime;
import java.util.Arrays;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

/**
 * A stress test to observe if the cache has a memory leak by not being able to drain the buffers
 * fast enough.
 *
 * @author ben.manes@gmail.com (Ben Manes)
 */
public final class Stresser {
  private static final int THREADS = 2 * Runtime.getRuntime().availableProcessors();
  private static final long STATUS_INTERVAL = 5;
  private static final int LENGTH = (1 << 20);
  private static final int MASK = LENGTH - 1;

  private final Cache<Integer, Integer> cache;
  private final Integer[] ints;
  private final long startTime;

  public Stresser() {
    Executors.newSingleThreadScheduledExecutor()
        .scheduleAtFixedRate(this::status, STATUS_INTERVAL, STATUS_INTERVAL, SECONDS);
    cache = CacheBuilder.newBuilder()
        .maximumSize(LENGTH)
        .build();

    startTime = System.nanoTime();
    ints = new Integer[LENGTH];
    Arrays.setAll(ints, key-> {
      cache.put(key, key);
      return key;
    });
    status();
  }

  public void run() throws InterruptedException {
    Runnable task = () -> {
      int index = ThreadLocalRandom.current().nextInt();
      for (;;) {
        cache.getIfPresent(ints[index++ & MASK]);
      }
    };
    Executor executor = Executors.newCachedThreadPool();
    for (int i = 0; i < THREADS; i++) {
      executor.execute(task);
    }
  }

  private void status() {
    long allocatedMemory = Runtime.getRuntime().totalMemory();
    long freeMemory = Runtime.getRuntime().freeMemory();
    long maxMemory = Runtime.getRuntime().maxMemory();

    long runningTime = TimeUnit.NANOSECONDS.toSeconds(System.nanoTime() - startTime);
    String elapsedTime = LocalTime.ofSecondOfDay(runningTime).toString();
    System.out.printf("---------- %s ----------%n", elapsedTime);
    System.out.printf("Allocated Memory = %,d bytes%n", allocatedMemory);
    System.out.printf("Free Memory = %,d bytes%n", freeMemory);
    System.out.printf("Max Memory = %,d bytes%n", maxMemory);
    System.out.println();
  }

  public static void main(String[] args) throws Exception {
    new Stresser().run();
  }
}

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