NIFI-8964 Add Cluster Firewall Configuration to Admin Guide

[exceptionfactory]

Description of PR

NIFI-8964 Adds a Cluster Firewall Configuration section under the general Clustering Configuration heading in the NiFi System Adminstrator's Guide. The section includes an example configuration file showing supported file syntax.

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[markobean]

Could you add more info on what "standard hostname resolution" means? For example, I believe NiFi has no inherent ability to resolve an IP address. This capability relies on that of the host.

[exceptionfactory]

What do you think about changing it to read as follows?

NiFi uses standard Java host name resolution to convert names to IP addresses. Java host name resolution leverages a combination of local machine configuration and network services, such as DNS.

[markobean]

Yes, that looks good. Thanks.

[exceptionfactory]

Thanks, I appreciate the feedback!

[markobean]

Good examples, particularly showing how comments can be used

[markobean]

It may require a separate JIRA ticket for tracking purposes, but I happen to notice just now that the Admin Guide states nifi.provenance.repository.rollover.time is 30 secs, but in reality it appears to be 10 mins (in the default nifi.properties file.)
Do you want to add it here while updating the guide? If not, let me know, and I'll create a separate JIRA ticket.

[exceptionfactory]

It may require a separate JIRA ticket for tracking purposes, but I happen to notice just now that the Admin Guide states nifi.provenance.repository.rollover.time is 30 secs, but in reality it appears to be 10 mins (in the default nifi.properties file.)
Do you want to add it here while updating the guide? If not, let me know, and I'll create a separate JIRA ticket.

Thanks for catching that additional detail and for the feedback on this PR. Given the current scope, I think it would be better to address that in a separate Jira issue with additional context and focus.

[markobean]

Built and installed this branch to confirm the Admin Guide renders as expected. Looks good.
The only nit-pick is not mentioning that text after a # character (even if not the first character of the line) are considered a comment and ignored. It is only mentioned that lines beginning with # are ignored. However, the example illustrates this behavior, so I won't belabor the point.
Other than that optional suggestion, +1

[markap14]

Thanks @exceptionfactory for the update to the admin guide! And thanks for reviewing @markobean. I'm a +1 as well. Merged to main.