topic How to tell if Splunk is dropping packets? in Knowledge Management

How to tell if Splunk is dropping packets?

rmcdougal — Wed, 05 Sep 2012 15:06:21 GMT

Simple question, We are forwarding a large amount of traffic to our indexer on port 514 and want to know if any packets are being dropped. Is there any easy way to do this? We are running our indexer on Windows 2008 R2

Re: How to tell if Splunk is dropping packets?

Drainy — Wed, 05 Sep 2012 20:57:23 GMT

Well they could be dropped before Splunk event knows about them assuming you're using UDP. Only sure way to tell would be to run a packet capture on either end.

In terms of Splunkyness, if its internal queues block far enough back it can cause it to drop packets as it cannot accept them. Easiest way to tell is to run a search for

index=_internal *blocked*

The best way would be to install the Splunk on Splunk (SoS) app though 🙂 Its excellent, it provides dashboards for all diagnostic purposes so you can monitor for problems.

If you are worried about data not arriving then you'd be better off using syslog over TCP or just installing a Splunk Universal Forwarder and sending it through that.

Re: How to tell if Splunk is dropping packets?

jonuwz — Wed, 05 Sep 2012 21:28:23 GMT

netstat -s

There's a line for 'Received Packets Discarded'

This is an indicator that the application isn't reading the traffic fast enough, the buffers are filling, and the kernel is discarding the extra packets.

disclaimer - i'm not on a windows machine at the moment, I cant remember if this covers udp packets on windows - it does on unix.

experiment with some of the other nestat options (keeping -s) to limit it to udp (maybe -p udp )