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From Erick Erickson <>
Subject Re: Legacy replication slave node full sync
Date Thu, 22 Mar 2018 22:17:40 GMT
1a> Replication pulls down changed segments, which includes _changed_
segments. Say I have 10 segments in my index and they all get merged
into a single segment that now contains the entire index. Then the
changed segment is replicated.

1b> If you're polling interval is such that all the segments get
replaced between synchronizations, then the entire index will be fetch
at the next poll.

2> You can turn on infoStream logging, see the reference guide.
WARNING: this will produce a _lot_ of output.

Why is this important? It's expected that occasionally a replication
may pull down the entire index, doing a forceMerge on the master for
instance. If you're saying that occasionally replication _replaces
existing segments_ with fresh ones of the same name from the master,
then that's a mystery. If you're saying that occasionally all the
segments are pulled from the master and all the old segments are
deleted from the slave, then that's expected, in this case there will
be no segments in common.


On Thu, Mar 22, 2018 at 11:10 AM, Yunee Lee <> wrote:
> Hi,
> I have two questions regarding legacy master /slave node replication architecture.
> We noticed that slave node does full sync time to time.
>   1.  What type of  event or configuration does trigger the full sync in slave node?
> I can not locate exact time and frequency from the logs. Please let me know.
>   2.  If  master nodes’  index merges  is related to trigger the full sync replication,
 then how can I find the index merge logging in solr log from master node?
> Please share the documentation if I can reference.
> Thanks.

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