[Transactions] Add pulsar-admin commands to lookup Coordinators

[eolivelli]

Search before asking

• I searched in the issues and found nothing similar.

Motivation

Actually there is no way using pulsar-admin to get the list of coordinators and to know which broker is running them.

I am using this command
bin/pulsar-admin topics partitioned-lookup pulsar/system/transaction_coordinator_assign

There are a few problems:

• it is basically impossible to users to know that you can do it (I had to look at Pulsar code)
• it returns information about only topics that are currently owned

Also I have observed that listing the topics inside pulsar/system returns an empty list even while disabling authn/authz
This should be unblocked in order to allow troubleshooting

Solution

Add a new command
pulsar-admin transactions list-coordinators

the command should list:

• the coordinator
• the coordinator id (used by other commands)
• the broker that is running the service

Alternatives

No response

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[michaeljmarshall]

What kind of authorization will pulsar-admin transactions list-coordinators require?

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