SOLR 4.8.0 Master/Slave Replication Issues

[Pouliot, Scott]

So we've been having oddball replication issues between master and slave (Not 
SOLRCloud) for a few weeks now.  Some days...everything lines up just fine.  
Other days things are off by a small amount between master and slave.

Here is the config on the MASTER server replication config:

<!-- ReplicationHandler -->
  <requestHandler name="/replication" class="solr.ReplicationHandler" >
    <lst name="master">
      <!--Replicate on 'startup' and 'commit'. 'optimize' is also a valid value 
for replicateAfter. -->
      <str name="replicateAfter">startup</str>
      <str name="replicateAfter">commit</str>

      <!--The default value of reservation is 10 secs.See the documentation 
below . Normally , you should not need to specify this -->
      <str name="commitReserveDuration">00:00:10</str>
    </lst>
    <!-- keep only 1 backup.  Using this parameter precludes using the 
"numberToKeep" request parameter. (Solr3.6 / Solr4.0)-->
    <!-- (For this to work in conjunction with "backupAfter" with Solr 3.6.0, 
see bug fix https://issues.apache.org/jira/browse/SOLR-3361 )-->
    <str name="maxNumberOfBackups">1</str>
  </requestHandler>    

Here is the SLAVE server replication config:

<requestHandler name="/replication" class="solr.ReplicationHandler" >
    <lst name="slave">

      <!--fully qualified url to the master core. It is possible to pass on 
this as a request param for the fetchindex command-->
      <str name="masterUrl">http://server01:8080/solr/${solr.core.name}</str>

      <!--Interval in which the slave should poll master .Format is HH:mm:ss . 
If this is absent slave does not poll automatically.
         But a fetchindex can be triggered from the admin or the http API -->
      <str name="pollInterval">00:01:00</str>
    </lst>
  </requestHandler>  

It seems very sporadic at best.  Sometimes I can manually click "Replicate Now" 
from the replication page in the SOLR UI and it will work, sometimes it does 
nothing.  Sometimes I can go to the master server, and if the "Optimize" button 
is available and I click it....it will replicate as soon as the Optimization is 
done.

Is this a bug in SOLR?  Could we possibly have some settings out of whack here? 
 I've been digging around online for a bit and not finding much info here.

This is on an older version of SOLR though, so wondering if maybe it used to be 
a bug?

Thanks!

Scott