[improve][broker] Support showing client ip address in client stats while using reverse proxy

[rdhabalia]

Motivation

In Apache Pulsar, the broker enables producers and consumers to connect to a topic and provides an API to retrieve topic statistics. These stats include a list of connected producers and consumers, along with their IP addresses and connection times. This information is particularly valuable when dealing with a large number of producers and consumers from various client hosts, as it helps troubleshoot issues such as:

Identifying which client host has an active consumer
Detecting if a client host has stopped consuming messages
Diagnosing message backlogs
Thus, mapping the client host IP to the corresponding producer or consumer is crucial.

The Issue with Reverse Proxies
However, this mapping breaks when a reverse proxy is used between the client and broker. In such cases, the broker records only the proxy's IP address for all connected producers and consumers, making it difficult to identify the actual client host. Apache Pulsar supports multiple proxy solutions, such as Pulsar-Proxy and SNI Proxy, which further complicates troubleshooting by obscuring client IPs.

To resolve this, this PR ensures that when a client library connects to a broker via a proxy, it sends the actual client IP address. The broker then correctly identifies and records this IP in the stats API, mapping it to the appropriate producer or consumer. This approach abstracts the proxy layer from users, allowing them to see accurate client IPs without any additional effort.

This PR doesn't change client-broker protocol, API definition or configuration.

Modifications

Client lib sends an ip-address property when client lib detects a proxy, and the broker shows it in the client stats.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.71429% with 3 lines in your changes missing coverage. Please review.

Project coverage is 74.30%. Comparing base (bbc6224) to head (17c830e).
Report is 917 commits behind head on master.

Files with missing lines	Patch %	Lines
...ava/org/apache/pulsar/broker/service/Consumer.java	50.00%	0 Missing and 1 partial ⚠️
...va/org/apache/pulsar/client/impl/ConsumerImpl.java	85.71%	0 Missing and 1 partial ⚠️
...va/org/apache/pulsar/client/impl/ProducerImpl.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #23974      +/-   ##
============================================
+ Coverage     73.57%   74.30%   +0.73%     
+ Complexity    32624    32311     -313     
============================================
  Files          1877     1853      -24     
  Lines        139502   143862    +4360     
  Branches      15299    16347    +1048     
============================================
+ Hits         102638   106902    +4264     
+ Misses        28908    28575     -333     
- Partials       7956     8385     +429     

Flag	Coverage Δ
inttests	26.79% <61.90%> (+2.20%)	⬆️
systests	23.26% <57.14%> (-1.06%)	⬇️
unittests	73.84% <85.71%> (+0.99%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ava/org/apache/pulsar/broker/service/Producer.java	80.90% <100.00%> (+0.52%)	⬆️
.../java/org/apache/pulsar/client/impl/ClientCnx.java	73.23% <100.00%> (+1.45%)	⬆️
...java/org/apache/pulsar/common/naming/Metadata.java	80.00% <ø> (ø)
...ava/org/apache/pulsar/broker/service/Consumer.java	85.00% <50.00%> (-1.67%)	⬇️
...va/org/apache/pulsar/client/impl/ConsumerImpl.java	80.51% <85.71%> (+2.94%)	⬆️
...va/org/apache/pulsar/client/impl/ProducerImpl.java	84.25% <85.71%> (+0.66%)	⬆️

... and 1038 files with indirect coverage changes