Fix compatibility with connection_pool 2.4+

[casperisfine]

Fix: mperham/connection_pool#172
Ref: mperham/connection_pool#166

ConnectionPool descendants must accept checking(force: true).

When it's called, all the cached connection should be checked back in, and the Thread.current state reset.

Additionally, making Connection respond to close allow them to be automatically closed on fork.

@drbrain @tenderlove

[tisba]

The breaking tests seem to be quite unrelated to your change, @casperisfine 🤔

[tenderworks]

Looks like an error message was changed. @casperisfine would you mind updating the test to an assert_match or something?

[tisba]

@tenderworks @tenderlove I found it #145, can you trigger the build?

[tisba]

I was reproducing related issue we had in prod because of the issues that's been fixed here, and I thought I share how this case can be reproduced. Happy to confirm that 4.0.2 does indeed fix the issue.

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  
  gem "parallel", "1.22.1"
  gem "connection_pool", "2.4.0"

  # bad
  gem "net-http-persistent", "4.0.1"

  # good
  # gem "net-http-persistent", "4.0.2"
end

require "parallel"
require "net/http/persistent"

Net::HTTP::Persistent.new(name: "my_app_name").request(URI('http://example.com/awesome/web/service'))

puts "Parent: #{Process.pid}"
Parallel.map([42], in_processes: 1) do
  puts "Child: #{Process.pid}"
  sleep 0.1
end

This will crash with 4.0.1.