Deadlock-like behavior when new IndexWriter created

[Andrii Berezhynskyi]

Hi,

I have solr5.2.1 set up in master-slave configuration. Very often it
happens that solr slave starts replicating (I can see it in admin panel)
but it is getting stuck at 0% and never proceeds further. Usually restart
of slave helps.

Relevant logs from slave:

INFO  - 2015-08-11 07:56:00.184; org.apache.solr.handler.IndexFetcher;
Master's generation: 26
INFO  - 2015-08-11 07:56:00.188; org.apache.solr.handler.IndexFetcher;
Slave's generation: 25
INFO  - 2015-08-11 07:56:00.189; org.apache.solr.handler.IndexFetcher;
Starting replication process
INFO  - 2015-08-11 07:56:00.205; org.apache.solr.handler.IndexFetcher;
Number of files in latest index in master: 10
INFO  - 2015-08-11 07:56:00.209;
org.apache.solr.core.CachingDirectoryFactory; return new directory for
/var/solr/data/catalog_article_1_de_DE/data/index.20150811075600209
*INFO  - 2015-08-11 07:56:00.212;
org.apache.solr.update.DefaultSolrCoreState; Creating new IndexWriter...*
*INFO  - 2015-08-11 07:56:00.221;
org.apache.solr.update.DefaultSolrCoreState; Waiting until IndexWriter is
unused... core=catalog_article_1_de_DE*
INFO  - 2015-08-11 07:56:00.522; org.apache.solr.core.SolrCore;
[catalog_article_1_de_DE] webapp=/solr path=/select params={} hits=0
status=0 QTime=1
INFO  - 2015-08-11 07:56:03.654; org.apache.solr.core.SolrCore;
[catalog_article_1_de_DE] webapp=/solr path=/select params={} hits=0
status=0 QTime=1
....

here is relevant solrconfig.xml entries:

<updateHandler class="solr.DirectUpdateHandler2">
    <updateLog>
      <str name="dir">${solr.catalog_article_1_de_DE.data.dir:}</str>
    </updateLog>

    <autoCommit>
      <maxDocs>10000</maxDocs>
      <maxTime>300000</maxTime>
      <openSearcher>false</openSearcher>
    </autoCommit>
    <autoSoftCommit>
         <maxTime>15000</maxTime>
     </autoSoftCommit>
  </updateHandler>

<requestHandler name="/replication" class="solr.ReplicationHandler">
      <lst name="master">
        <str name="enable">${enable.master:false}</str>
        <str name="replicateAfter">optimize</str>
        <str name="confFiles">schema.xml,solrconfig.xml</str>
      </lst>
      <lst name="slave">
        <str name="enable">${enable.slave:false}</str>
        <str name="masterUrl">${master.url:127.0.0.1:8983}/${solr.core.name
}</str>
        <str name="pollInterval">00:01:00</str>
      </lst>
    </requestHandler>

Has anybody faced the same problem?
Is it master's or slave's issue?
How can I debug/fix the problem?

Thanks
Andrii