Xiao,
FileChannel.force is fsync on unix.
To force fsync on every message:
log.flush.interval.messages=1
You are looking at the time based fsync, which, naturally, as you say, is
time-based.
-Jay
On Fri, Mar 6, 2015 at 11:35 PM, Xiao <lixiao1...@gmail.com> wrote:
> Hi, Jay,
>
> Thank you for your answer.
>
> Sorry, I still do not understand your meaning.
>
> I guess the two parameters you mentioned are log.flush.interval and
> log.default.flush.interval.ms. However, these two parameters only control
> when Kafka issues a flush (i.e., calling FileChannel.force()).
>
> Fsync (fileOutputStream.getFD().sync()) is controlled by another parameter
> log.default.flush.scheduler.interval.ms.
>
> scheduler.schedule("kafka-recovery-point-checkpoint",
> checkpointRecoveryPointOffsets,
> delay = InitialTaskDelayMs,
> period = flushCheckpointMs,
> TimeUnit.MILLISECONDS)
>
> This thread is only time-controlled. It does not check the number of
> messages.
>
> Thank you,
>
> Xiao Li
>
>
> On Mar 5, 2015, at 11:59 AM, Jay Kreps <jay.kr...@gmail.com> wrote:
>
> > Hey Xiao,
> >
> > That's not quite right. Fsync is controlled by either a time based
> criteria
> > (flush every 30 seconds) or a number of messages criteria. So if you set
> > the number of messages to 1 the flush is synchronous with the write,
> which
> > I think is what you are looking for.
> >
> > -Jay
>
>
