Snappy cannot encode records larger than ~3.7 GB and will panic if an encoding is attempted. Check to make sure that the record is smaller than this before encoding. In the future, we could improve this behavior to still compress large records (or break them up into smaller records), but this avoids the panic for users with very large single scrape targets. Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>