in impl/src/main/java/org/apache/rocketmq/remoting/internal/UIDGenerator.java [84:95]
public String createUID() {
long current = System.currentTimeMillis();
if (current >= nextStartTime) {
setStartTime(current);
}
buffer.position(0);
sb.setLength(basePos);
buffer.putInt((int) (System.currentTimeMillis() - startTime));
buffer.putShort(counter++);
sb.append(ByteUtils.toHexString(buffer.array()));
return sb.toString();
}