InputLocationTracker tracker) {
        if (!validateNotNull(prefix, fieldName, problems, severity, version, string, sourceHint, tracker)) {
            return false;
        }

        if (!string.isEmpty()) {
            return true;
        }

        addViolation(problems, severity, version, prefix + fieldName, sourceHint, "is missing.", tracker);

        return false;
    }

-   Our users' guide, [Guava Explained]
-   [A nice collection](https://www.tfnico.com/presentations/google-guava) of
    other helpful links

## Links

-   [GitHub project](https://github.com/google/guava)
-   [Issue tracker: Report a defect or feature request](https://github.com/google/guava/issues/new)
-   [StackOverflow: Ask "how-to" and "why-didn't-it-work" questions](https://stackoverflow.com/questions/ask?tags=guava+java)

	for i, b := range pd.QueuedBuckets {
		if b == bucket {
			// Bucket is done.
			pd.QueuedBuckets = append(pd.QueuedBuckets[:i], pd.QueuedBuckets[i+1:]...)
			// Clear tracker info.
			if pd.Bucket == bucket {
				pd.Bucket = "" // empty this out for next bucket
				pd.Prefix = "" // empty this out for the next bucket
				pd.Object = "" // empty this out for next object
			}

			}
		case <-p.mrfWorkerKillCh:
			return
		}
	}
}

// AddWorker adds a replication worker to the pool.
// An optional pointer to a tracker that will be atomically
// incremented when operations are running can be provided.
func (p *ReplicationPool) AddWorker(input <-chan ReplicationWorkerOperation, opTracker *int32) {
	for {
		select {