@Override
    public String toString() {
        return "LockMetrics{" +
                "acquireCount=" + acquireCount +
                ", acquireFailedCount=" + acquireFailedCount +
                ", acquireTimedOutCount=" + acquireTimedOutCount +
                ", acquireSucceededCount=" + acquireSucceededCount +
                ", releaseCount=" + releaseCount +
                ", releaseFailedCount=" + releaseFailedCount +
                ", reentryCount=" + reentryCount +
                ", cumulativeAcquireCount=" + cumulativeAcquireCount +
                ", cumulativeAcquireFailedCount=" + cumulativeAcquireFailedCount +
                ", cumulativeAcquireTimedOutCount=" + cumulativeAcquireTimedOutCount +
                ", cumulativeAcquireSucceededCount=" + cumulativeAcquireSucceededCount +
                ", cumulativeReleaseCount=" + cumulativeReleaseCount +
                ", cumulativeReleaseFailedCount=" + cumulativeReleaseFailedCount +
                ", cumulativeReentryCount=" + cumulativeReentryCount +
                ", acquireStats=" + acquireStats +
                ", lockedStats=" + lockedStats +
                '}';
    }
Returns a Runnable that must be invoked when the acquire() finishes.
zkfacade/src/main/java/com/yahoo/vespa/curator/stats/LockMetrics.java