DocExpirationUpdateProcessorFactory not deleting records

[S.L]

I am trying to use the DocExpirationUpdateProcessorFactoryfactory in Solr
4.10.1 version.

I have included the following in my solrconfig.xml

    <updateRequestProcessorChain default="true">
        <processor class="solr.UUIDUpdateProcessorFactory">
            <str name="fieldName">id</str>
        </processor>

        <processor class="solr.TimestampUpdateProcessorFactory">
            <str name="fieldName">timestamp</str>
        </processor>
        <processor
class="solr.processor.DocExpirationUpdateProcessorFactory">
            <int name="autoDeletePeriodSeconds">30</int>
            <str name="ttlFieldName">ttl</str>
            <str name="expirationFieldName">expire_at</str>
        </processor>
        <processor class="solr.LogUpdateProcessorFactory" />
        <processor class="solr.RunUpdateProcessorFactory" />
    </updateRequestProcessorChain>

And I have included the following in my schema.xml

        <field name="timestamp" type="date" indexed="true" stored="true"
default="NOW" multiValued="false"/>
        <field name="ttl" type="date" indexed="true" stored="true"
default="NOW+60SECONDS" multiValued="false"/>
        <field name="expire_at" type="date" indexed="true" stored="true"
multiValued="false"/>

As you can see I am setting the time to live to be 60 seconds and checking
to delete every 30 seconds, when I insert a document , and check after a
minute or couple or an hour it never gets deleted.

This is  what I see in the indexed document , can you please let me know
what might be the issue here ? Please note that the expire_at field is
never getting generated in the Solr document as can be seen below.



    "id": "3888a8ac-fbc4-437a-8248-132384753c00",
    "timestamp": "2015-02-04T04:09:21.29Z",
    "_version_": 1492147724740460500,
    "ttl": "2015-02-04T04:10:21.29Z"