NIFI-6740: Add configuration options to specify NiFi/Bootstrap communication ports

[stevedlawrence]

Description of PR

The NiFi and NiFi Bootstrap processes both bind to random ephemeral
ports to allow for inter-process communication (e.g. shutdown, port,
ping, etc.). However, the randomness of these ephemeral ports can pose
challenges for some security policies and firewall rules.

This adds two configuration options, nifi.bootstrap.listen.port and
nifi.listener.bootstrap.port, that allow an administrator to define
which ports the two processes should bind to for this communication,
making it easier to define security policies. The options default to
zero to maintain the current ephemeral port behavior.

fixes bug NIFI-6740

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[mattyb149]

This always has to match the one in bootstrap, right? It will get sent to the NiFi process when the bootstrap starts it, so I don't think we need the property on the NiFi side.

[stevedlawrence]

My understanding is that they must be different.

Bootstrap will start and listen on nifi.bootstrap.listen.port. It will then start the main NiFi process and pass an argument that tells that main NiFi process what port Bootstrap is listening on.

Then when NiFi starts, it will start listening on nifi.listener.bootstrap.port, and send a message to Bootstrap (to the port bootstrap is listening on, i.e. nifi.bootstrap.listen.port) telling it what this port it started listening on. At this point, each process is listening on a different port and knows which port the other is listening on to send commands.

By default these ports are random ephemeral ports, hence this communication needed to tell each other what the ports the other is listening on. This patch just makes it so you can optionally specify non-random ports.

[mattyb149]

Ah I conflated the names nifi.bootstrap.listen.port and nifi.listener.bootstrap.port, my bad

[mattyb149]

Maybe more detail in the comment about what the port property means/does?

[stevedlawrence]

Yeah, the names are a bit confusing, I'm open to other suggestions that might be more clear.

I've added a comment as suggested.

[mattyb149]

+1 LGTM, verified the expected behavior. Thanks for the improvement! Merged to main