private synchronized void completeTickThreadStage() {
        // This is expected behavior with nested stages; can just no-op
        if (tickThreadStage == null)
            return;

        log.trace("Completing current tick thread stage; was {}", tickThreadStage);

        tickThreadStage.complete(time.milliseconds());
        tickThreadStage = null;
    }
Checks a given {@link InternalRequestSignature request signature} for validity and adds an exception
to the given {@link Callback} if any errors are found.

@param requestSignature the request signature to validate
@param callback callback to report invalid signature errors to
@return true if the signature was not valid
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java