Add the ability to provide a list of hosts for a connection

[javanthropus]

This change adds the ability to provide a list of hosts to try when opening a connection while maintaining backward compatibility with existing code. If a list is provided, it overrides the individual host and port settings; otherwise, the individual settings are used as a single element list.

The host list is a simple object that responds to each and provides a hostname and port pair to a block. This allows for users to use any mechanism they need to provide a list of potential hosts. For instance, a randomized ordering for a static list could be used, or a list based on SRV record lookups could be provided.

In either case, failure of all servers is required in order to fail opening a connection. A Net::LDAP::Error instance that summarizes all of the server failures is raised in this case. If any server succeeds, usage proceeds as usual. This includes setting up encryption if requested.

[javanthropus]

I forgot to mention that this PR provides a way to tackle #191 that avoids pulling in any additional dependencies into this project.

I also have another change ready to go that DRYs up some of the connection creation and error handling logic between when sockets are given as opposed to host-port pairs. I didn't include it here because it changes the messages of the error messages a bit, basically just wraps the original exception messages when raising Net::LDAP::Error and Net::LDAP::ConnectionRefusedError for them rather than include custom messages.

I can either add that commit here or apply it as a separate PR that builds on the result of accepting this PR so that it can be considered independently. Let me know.

[jch]

Why to_enum here? hosts is already an iterable object?

[javanthropus]

That was a late night edit, I think. I was trying to make sure that the
object passed in only responded to the each method so that the test
enforces the contract and doesn't allow the code to start using other
methods.

For now, I'll probably just chuck the to_enum calls unless you would
prefer the enforcement. It shouldn't too hard to make a simple wrapper
class to mask out the other methods though.

On Mon, Sep 28, 2015, 15:12 Jerry Cheung notifications@github.com wrote:

In test/test_ldap_connection.rb
#223 (comment)
:

@@ -9,6 +9,44 @@ def capture_stderr
$stderr = stderr
end

• def test_list_of_hosts_with_first_host_successful
• hosts = [

•          ['test.mocked.com', 636],
  

•          ['test2.mocked.com', 636],
  

•          ['test3.mocked.com', 636],
  

•        ]
  

• flexmock(TCPSocket).should_receive(:new).ordered.with(*hosts[0]).once.and_return(nil)
• flexmock(TCPSocket).should_receive(:new).ordered.never
• Net::LDAP::Connection.new(:hosts => hosts.to_enum(:each))

Why to_enum here? hosts is already an iterable object?

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[jch]

Looking good. Thanks for getting this started!

[jch]

🎉