Well, the docs state that you would need two machines, 1 online and 1 offline. Prepare the pack on the online machine then copy the pack over to the offline machine and install it. You have to have some access to the offline machine in order to copy the
gem file to it surely.
A major problem with using the
gem file method is that, if the gem has dependencies it needs it will try to download them and fail. This is not a Logstash problem per se, this is how the Ruby Gem ecosystem works.
We switched to using the offline pack method because the online install will install deps on the local machine and then they are available in the pack.
PS. you need not be so disparaging - you are using a free-of-charge open source project that is using other FOC OS projects to do a lot of the infrastructure stuff like managing plugins, talking to kafka, netflow, jdbc, AWS S3 etc.