collecting custom metrics

Hi Guys,

Apart from standard metrics I would like to gather body length. For instance, if I request for an image, besides a response time, I would also like to know the size of the image.
This data would be stored in influxDB later on.

Apparently in Gatling 2.3 extraInfoExtractor was used for this purpose, but it has been removed in Gatling 3.0.

How can I extract body size and add it to symulation.log?

Thank you in advance for any help.