private void messageSent(int size, long sendTimeNanos, Exception exception) {
        if (exception != null) {
            stats.messageFailed();
        } else {
            stats.messageSent(size, sendTimeNanos);
        }
    }
Partitions that are ready to be consumed.
Only used during the initial topic readiness check, which is, {@link #preparing} is true.
tools/src/main/java/org/apache/kafka/tools/automq/PerfCommand.java