Where's my time going mysteriously? - ruby

Question

I have a ruby script that uses rsolr rubygem to generate XMLs and POST them to Apache Solr (javadoc Update Command) surfaced by Jetty Server. My script logs certain time using the following code
405 unless docs.empty?
406 begin
407 log.info("Adding to solr")
408 response = solr.add(docs)
409 log.info("#{(id_2*100.0)/last_id}% Done")
410 if response['responseHeader']['status'] != 0
411 log.fatal("Document ids not sent")
412 #log.fatal(Solr::Request::AddDocument.new(docs_single).to_s)
413 log.close
414 exit
415 end
416 log.info("#{Time.now.to_f - starttime}s to feed Solr. #{id_1} to #{id_2}")
417 rescue Exception => e
418 log.fatal("Document ids not sent => ")
419 #log.fatal(Solr::Request::AddDocument.new(docs_single).to_s)
420 #log.fatal(docs)
421 log.close
422 exit
423 end
The log generated goes like
I, [2011-10-09T15:03:42.617048 #30092] INFO -- : Executing - SELECT * FROM solr_feeddata_2 WHERE id >= 5879999 AND id < 5881999
I, [2011-10-09T15:03:44.086661 #30092] INFO -- : External Data1 fetch time: 1.45462989807129
I, [2011-10-09T15:03:44.109514 #30092] INFO -- : External Data2 fetch time: 0.0226790904998779
I, [2011-10-09T15:03:44.109611 #30092] INFO -- : 1.49255704879761s to fetch details from database. 5879999 to 5881999
I, [2011-10-09T15:03:44.109702 #30092] INFO -- : Adding data1, data2, building docs
I, [2011-10-09T15:03:45.912603 #30092] INFO -- : 3.29554414749146s to build documents. 5879999 to 5881999
I, [2011-10-09T15:03:45.912730 #30092] INFO -- : Adding to solr
I, [2011-10-09T15:04:24.797620 #30092] INFO -- : 61.180855194502% Done
I, [2011-10-09T15:04:24.797744 #30092] INFO -- : 42.180694103241s to feed Solr. 5879999 to 5881999
According to this log, Solr took (42.18 - 3.29 - 1.49 - 2) 35.4s to respond. (See below comment)
At the same time my Solr log for this particular update goes like
INFO: {add=[5879999, 5880000, 5880001, 5880002, 5880003, 5880004, 5880005, 5880007, ... (1468 adds)]} 0 5780
Oct 9, 2011 3:04:24 PM org.apache.solr.core.SolrCore execute
INFO: [core0] webapp=/solr path=/update params={wt=ruby} status=0 QTime=5780
Oct 9, 2011 3:04:42 PM org.apache.solr.update.processor.LogUpdateProcessor finish
This clearly shows that Solr took 5.78s to add the docs, initiate response send and closed the log updater.
Both the services run on same machine, inside the network, and their ping summary is
rtt min/avg/max/mdev = 0.008/0.010/0.022/0.006 ms
This pattern is clearly visible for every batch data processed. Despite my sincere efforts to get this mystery out, I am not able to get the reason for this behavior.
My Solr mergeFactor is 10, autoCommit is off.