On 4/9/2015 11:20 AM, Ted Cao wrote:
> This may not be an issue with most people but here is my finding and
> way of reproducing this:
>
> Download 4.5 solr, using the collections1 sample, turn on 15 seconds
> auto commit (with or without transaction logs) on with
> <nrtMode>true</nrtMode> which is default, update/add to solr
> constantly every second for 3 minutes, hard crash and bring solr back
> up, everything works perfectly with no data loss. Now turn nrtMode
> (near real time mode) = false, and do the same test, you will find
> data loss, data are not consistently written to disk, I lose lots of
> adds/updates.
>
> I read from this ticket
> https://issues.apache.org/jira/browse/SOLR-6897
> that nrtMode was really mainly for testing and removed in later
> version (unlike in the comments where it said it should be false in
> master/slave), so I assume nrtMode should always be true, even with a
> write only master with autocommit turned on
>
> so,
> 1) is the "bug"/"behavior" I am reporting plausible? It's very easy to
> reproduce as I noted above
> 2) Is it OK to always set nrtMode=true in solr 4.5, what other
> negative consequence could there be?

Since nrtMode is gone in 5.0, this should not be a problem in that
version.  The 4.x code is in maintenance mode, which means that we don't
backport a change unless it fixes a major bug without a workaround or it
is a trivial change that makes a large difference in usability and
doesn't break any existing functionality.  These are loose requirements,
not rules, but we try *really* hard to only make changes in that branch
that we think are completely safe.

This particular bug is in a feature that wasn't really intended to be
used by the public, it has a workaround, and it does not affect the
current stable branch.  That does not meet the loose requirements for a
change to the previous stable branch in maintenance mode.

Based on the discussion in SOLR-6897, I think it is perfectly acceptable
to always use nrtMode=true, and negative consequences are not likely.  I
personally would remove the nrtMode config entirely, since default
behavior is acceptable.

Thanks,
Shawn


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