Solr "replicateAfter optimize" is specified, but replication starts also on commits and master startup (tested on solr 5.5.2)

[Alessandro Bon]

Hi everyone,
I am experiencing a replication issue on a master/slave configuration,

Issue: Full index replicas occur sometimes on master startup and after commits, 
despite only the <str name="replicateAfter">optimize</str> directive is 
specified. In the case of replica on commit, it occurs only for sufficiently 
big commits. Replica correctly starts again at the end of my indexing job, 
after the optimization phase. As result of this behaviour I get incomplete 
indexes on slaves during the indexing process.
Solr version: 5.5.2
Configuration:

<config>
    
<abortOnConfigurationError>${solr.abortOnConfigurationError:true}</abortOnConfigurationError>

    <luceneMatchVersion>5.5.1</luceneMatchVersion>

    <dataDir>${solr.data.dir:}</dataDir>

    <directoryFactory name="DirectoryFactory"
                      
class="${solr.directoryFactory:solr.StandardDirectoryFactory}"/>

    <indexConfig>
        <writeLockTimeout>1000</writeLockTimeout>
        <useCompoundFile>false</useCompoundFile>
        <ramBufferSizeMB>32</ramBufferSizeMB>
        <mergePolicyFactory 
class="org.apache.solr.index.TieredMergePolicyFactory">
           <int name="maxMergeAtOnce">10</int>
           <int name="segmentsPerTier">10</int>
        </mergePolicyFactory>
        <lockType>native</lockType>
        <reopenReaders>true</reopenReaders>
        <deletionPolicy class="solr.SolrDeletionPolicy">
            <str name="maxCommitsToKeep">1</str>
            <str name="maxOptimizedCommitsToKeep">0</str>
        </deletionPolicy>
        <maxFieldLength>100000</maxFieldLength>
        <infoStream file="INFOSTREAM.txt">false</infoStream>
    </indexConfig>

    <jmx />

    <updateHandler class="solr.DirectUpdateHandler2">
        <autoCommit>
            <maxDocs>10000</maxDocs> <!-- maximum uncommited docs before 
autocommit triggered -->
            <maxTime>600000</maxTime> <!-- maximum time (in MS) after adding a 
doc before an autocommit is triggered -->
            <openSearcher>false</openSearcher>
        </autoCommit>
    </updateHandler>

    [...]

    <!--Replication from the Solr Master to the Slaves. The Job 
SrsIndexUpdateJob will create the index on the master which will be replicated 
on the slaves.-->
    <requestHandler name="/replication" class="solr.ReplicationHandler">
        <lst name="master">
            <str name="enable">${solr.master.enable:false}</str>
            <str name="replicateAfter">optimize</str>
            <str name="backupAfter">optimize</str>
        </lst>
        <str name="maxNumberOfBackups">${solr.numberOfVersionToKeep:3}</str>
        <lst name="slave">
            <str name="enable">${solr.slave.enable:false}</str>
            <str name="masterUrl">${solr.master.url:}/replication</str>
            <str 
name="pollInterval">${solr.replication.pollInterval:00:00:30}</str>
        </lst>
    </requestHandler>

    [...]

    </config>


Any idea on how to solve this issue would be greatly appreciated.

Many thanks,
Alessandro