Based on the current version of Splunk, there are 3 types of Forwarder configuration:
The universal forwarder is a streamlined, dedicated version of Splunk that contains only the essential components needed to forward data to receivers.
A heavy forwarder is a full Splunk instance, with some features disabled to achieve a smaller footprint.
A light forwarder is also a full Splunk instance, with most features disabled to achieve as small a footprint as possible.
The lightweight forwarder type is typically used to support previous versions of Splunk, and likely should not be needed in new installations. Now you simply need to decide if you need a heavy or Universal forwarder, and that decision usually comes down to whether or not you need to filter or route data from the forwarder.
In your example above, tagging source and hostname are actually part of the Splunk metadata - these elements are typically attached to your event data by default. In this case, you can use the Universal Forwarder.
If you plan to route event data to multiple hosts, or if you want to limit (filter) the data from the Forwarder to the indexer, then you'll need a heavy forwarder.
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