@Weak final Monitor monitor;
    final Condition condition;

    @GuardedBy("monitor.lock")
    int waiterCount = 0;

    /** The next active guard */
    @GuardedBy("monitor.lock")
    @CheckForNull
    Guard next;

    protected Guard(Monitor monitor) {
      this.monitor = checkNotNull(monitor, "monitor");
      this.condition = monitor.lock.newCondition();
    }

    /**

    if (e == null) throw new NullPointerException();
    final Monitor monitor = this.monitor;
    monitor.enterWhen(notFull);
    try {
      insert(e);
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable E poll() {
    final Monitor monitor = this.monitor;
    if (monitor.enterIf(notEmpty)) {
      try {
        return extract();

      @Override
      protected void runTest() throws Throwable {
        Monitor monitor = new Monitor(fair);
        FlagGuard guard = new FlagGuard(monitor);
        Object[] arguments =
            (timed ? new Object[] {guard, 0L, TimeUnit.MILLISECONDS} : new Object[] {guard});
        try {
          method.invoke(monitor, arguments);
          fail("expected IllegalMonitorStateException");

        return "stopping({from = " + from + "})";
      }
    };
  }

  private final Monitor monitor = new Monitor();

  private final Guard isStartable = new IsStartableGuard();

  @WeakOuter
  private final class IsStartableGuard extends Guard {
    IsStartableGuard() {
      super(AbstractService.this.monitor);
    }

    @Override
    public boolean isSatisfied() {
      return state() == NEW;

        }
      }
    }
  }

  /** A guard that encapsulates a simple, mutable boolean flag. */
  static class FlagGuard extends Monitor.Guard {

    private boolean satisfied;

    protected FlagGuard(Monitor monitor) {
      super(monitor);
    }

    @Override
    public boolean isSatisfied() {
      return satisfied;
    }

    public void setSatisfied(boolean satisfied) {

  @Override
  public <T> T[] toArray(T[] a) {
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return q.toArray(a);
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public String toString() {
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return q.toString();

import org.opensearch.monitor.jvm.JvmStats;
import org.opensearch.monitor.jvm.JvmStats.BufferPool;
import org.opensearch.monitor.jvm.JvmStats.Classes;
import org.opensearch.monitor.jvm.JvmStats.GarbageCollectors;
import org.opensearch.monitor.jvm.JvmStats.Mem;
import org.opensearch.monitor.jvm.JvmStats.Threads;
import org.opensearch.monitor.os.OsProbe;
import org.opensearch.monitor.os.OsStats;

    if (e == null) throw new NullPointerException();
    final Monitor monitor = this.monitor;
    monitor.enterWhen(notFull);
    try {
      insert(e);
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable E poll() {
    final Monitor monitor = this.monitor;
    if (monitor.enterIf(notEmpty)) {
      try {
        return extract();

  @Override
  public <T> T[] toArray(T[] a) {
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return q.toArray(a);
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public String toString() {
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return q.toString();

  private static final class ServiceManagerState {
    final Monitor monitor = new Monitor();

    @GuardedBy("monitor")
    final SetMultimap<State, Service> servicesByState =
        MultimapBuilder.enumKeys(State.class).linkedHashSetValues().build();

    @GuardedBy("monitor")
    final Multiset<State> states = servicesByState.keys();

    @GuardedBy("monitor")