@Override
        public void onCompletion(RecordMetadata metadata, Exception exception) {
            long now = Time.SYSTEM.milliseconds();
            long durationMs = now - startMs;
            sendRecords.recordDuration(durationMs);
            if (exception != null) {
                log.error("SendRecordsCallback: error", exception);
            }
        }
This workload allows for customized and even variable configurations in terms of messages per second, message size,
batch size, key size, and even the ability to target a specific partition out of a topic.

See `ConfigurableProducerSpec` for a more detailed description.
trogdor/src/main/java/org/apache/kafka/trogdor/workload/ConfigurableProducerWorker.java