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From Nawab Zada Asad Iqbal <khi...@gmail.com>
Subject Re: TLog for non-Solrcloud scenario
Date Mon, 29 May 2017 19:47:23 GMT
Thanks Erick,

I have read different documents in this area and I am getting confused due
to overloaded/"reused" terms.

E.g., in that lucidworks page, the flow for an indexing request is
explained as follows. This makes me think that at the time of soft-commit,
the documents in preceding update requests are already flushed (might not
be on the disk yet, but JVM has handed over the responsibility to Operating
system). (even if we don't do it as part of soft-commit)

"After all the leaders have responded, the originating node replies to the
client. At this point,

*all documents have been flushed to the tlog for all the nodes in the
cluster!"*

On Mon, May 29, 2017 at 7:57 AM, Erick Erickson <erickerickson@gmail.com>
wrote:

> There's a long post here on this that might help:
>
> https://lucidworks.com/2013/08/23/understanding-
> transaction-logs-softcommit-and-commit-in-sorlcloud/
>
> Short form: soft commit doesn't flush tlogs, does not start a new
> tlog, does not close segments, does not open new segments.
>
> Hard commit does all of these things.
>
> Best,
> Erick
>
> On Sun, May 28, 2017 at 3:59 PM, Nawab Zada Asad Iqbal <khichi@gmail.com>
> wrote:
> > Hi,
> >
> > SolrCloud document <https://wiki.apache.org/solr/NewSolrCloudDesign>
> > mentions:
> >
> > "The sync can be tunable e.g. flush vs fsync by default can protect
> against
> > JVM crashes but not against power failure and can be much faster "
> >
> > Does it mean that flush protects against JVM crash but not power failure?
> > While fsync will protect against both scenarios.
> >
> >
> > Also, this NRT help
> > <https://cwiki.apache.org/confluence/display/solr/Near+
> Real+Time+Searching>
> > explains soft commit as:
> > "A *soft commit* is much faster since it only makes index changes visible
> > and does not fsync index files or write a new index descriptor. If the
> JVM
> > crashes or there is a loss of power, changes that occurred after the
> last *hard
> > commit* will be lost."
> >
> > This is little confusing, as a soft-commit will only happen after a tlog
> > entry is flushed. Isn't it? Or doesn't tlog work differently for
> solrcloud
> > and non-solrCloud configurations.
> >
> >
> > Thanks
> > Nawab
>

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