If time is not specified explicitly for point - current time in millis is used. So if several points having the same measurement name are generated one right after another - they will have same time field. And InfluxDB will save only last of them

The current workaround with sleep between generating points looks too slow for cases with a big number of points.

I suggest next fix. Time should be defaulted for every point built by abstract generator class with value of
builder.time(timeGenerator.getTimeNanos(), TimeUnit.NANOSECONDS);

where timeGenerator is a member of generator having class :

// generates unique nano timestamps

private static class TimeGenerator {
private final long nanoTimeShift;
private long lastReportedTime = 0;

TimeGenerator() {
nanoTimeShift = System.currentTimeMillis() * 1000000 - System.nanoTime();
}

long getTimeNanos() {
long timeToReport = System.nanoTime() + nanoTimeShift;
if (timeToReport <= lastReportedTime) {
timeToReport = lastReportedTime + 1;
}
lastReportedTime = timeToReport;
return timeToReport;
}
}