RUBY-3743 Correctly implement srv_max_hosts option

[kyleburgess2025]

This finishes the implementation of the spec changes for DRIVERS-1519:

• Changes SRV monitoring to correctly use the srv_max_hosts option
• Fixes the bug that prevented the srv_max_hosts option in the Mongo client builder from being used
• Changes the default for raise_on_invalid in the SRV resolver to false to adhere to spec requirements

[Copilot]

Pull request overview

This PR implements spec changes from DRIVERS-1519 for SRV monitoring with srvMaxHosts support. The changes ensure that the srv_max_hosts parameter is properly passed through the monitoring system and that SRV resolution failures are handled according to specification requirements.

Key Changes:

• Modified SRV resolver to not raise errors on invalid domain verification per spec
• Updated SRV monitor and URI parser to pass through srv_max_hosts and srv_service_name options from both URI and client options
• Added comprehensive test coverage for srv_max_hosts functionality in the SRV monitor

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
spec/mongo/srv/monitor_spec.rb	Adds test cases verifying that srv_max_hosts limits cluster hosts and is correctly passed to the resolver
lib/mongo/uri/srv_protocol.rb	Changes resolver to use raise_on_invalid: false and adds fallback logic for srv_service_name and srv_max_hosts options
lib/mongo/srv/monitor.rb	Updates scan! method to pass srv_service_name and srv_max_hosts options to resolver

---

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[Copilot]

Removed trailing whitespace from lines 155 and 156.

Suggested change

	hostname,
	uri_options[:srv_service_name] || options[:srv_service_name],
	hostname,
	uri_options[:srv_service_name] || options[:srv_service_name],

[jamis]

Looks great! Optionally: cleaning up that line I mentioned in srv/resolver.rb, but that is clearly outside the scope of this ticket, so I'll leave that up to you.

[kyleburgess2025]

Locally tested these changes using the following script:

require 'logger'
require 'debug'

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  # gem 'mongoid', '~> 7.5.4'
  gem 'mongo', path: __dir__
end

Mongo::Logger.logger = Logger.new($stdout)
Mongo::Logger.logger.level = Logger::INFO

URL = 'mongodb+srv://test1.test.build.10gen.cc/?tls=false'

client = Mongo::Client.new(URL, connect_timeout: 5, server_selection_timeout: 10, socket_timeout: 5, srv_max_hosts: 1)
puts "==== size: #{client.cluster.addresses.size}"
sleep(5)
puts "==== size: #{client.cluster.addresses.size}"

URL_WITH_MAX_HOSTS = 'mongodb+srv://test1.test.build.10gen.cc/?tls=false&srvMaxHosts=1'
client2 = Mongo::Client.new(URL_WITH_MAX_HOSTS, connect_timeout: 5, server_selection_timeout: 10, socket_timeout: 5)
puts "==== size: #{client2.cluster.addresses.size}"
sleep(5)
puts "==== size: #{client2.cluster.addresses.size}"

Output:

W, [2026-01-05T10:44:44.023231 #72997]  WARN -- : MONGODB | Error checking localhost.test.build.10gen.cc:27017: Mongo::Error::SocketError: Errno::ECONNREFUSED: Connection refused - connect(2) for 127.0.0.1:27017 (for 127.0.0.1:27017 (no TLS)) (on localhost.test.build.10gen.cc:27017)
==== size: 1
==== size: 1
W, [2026-01-05T10:44:49.469193 #72997]  WARN -- : MONGODB | Error checking localhost.test.build.10gen.cc:27017: Mongo::Error::SocketError: Errno::ECONNREFUSED: Connection refused - connect(2) for 127.0.0.1:27017 (for 127.0.0.1:27017 (no TLS)) (on localhost.test.build.10gen.cc:27017)
==== size: 1
W, [2026-01-05T10:44:54.028700 #72997]  WARN -- : MONGODB | Error checking localhost.test.build.10gen.cc:27017: Mongo::Error::SocketError: Errno::ECONNREFUSED: Connection refused - connect(2) for 127.0.0.1:27017 (for 127.0.0.1:27017 (no TLS)) (on localhost.test.build.10gen.cc:27017)
==== size: 1