I haven't previously seen this 'feature' and I've only seen it now because it's not working properly.
Some of my AWS Cloudwatch logs have the host name set to the literal string $decideOnStartup. From other Answers, I gather this was supposed to have been fixed in Splunk 5. Well, this is Splunk 6.2.2 and AWS TA 1.1.1 so it isn't.
I noticed during the setup for the AWS TA that $decideOnStartup was the suggestion for the host name, and assumed -- silly me -- that Splunk would go ahead and figure it out.
How is this supposed to work, and is it a problem with Splunk or the TA?
please open a support ticket so we can diagnose.