[Experimental] Minimum support for Rails 6.1

[sergiogomez]

This PR is only replacing failing methods (only the detected ones) with new classes and methods from Rails 6.1.

[calos0921]

This PR is only replacing failing methods (only the detected ones) with new classes and methods from Rails 6.1.

But I use passenger have some errors.
I think the passenger have call ActiveRecord::Base.clear_all_connections!

undefined method `clear' for nil:NilClass (NoMethodError)
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:832:in `block in with_new_connections_blocked'
  /usr/local/rvm/rubies/ruby-2.7.8/lib/ruby/2.7.0/monitor.rb:202:in `synchronize'
  /usr/local/rvm/rubies/ruby-2.7.8/lib/ruby/2.7.0/monitor.rb:202:in `mon_synchronize'
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:828:in `ensure in with_new_connections_blocked'
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:845:in `with_new_connections_blocked'
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:747:in `with_exclusively_acquired_all_connections'
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:494:in `disconnect'
  /usr/local/rvm/gems/ruby-2.7.8/gems/activerecord-6.1.7.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:516:in `disconnect!'
  /usr/local/rvm/gems/ruby-2.7.8/bundler/gems/octopus-263b1b729079/lib/octopus/proxy.rb:256:in `block in with_each_healthy_shard'
  /usr/local/rvm/gems/ruby-2.7.8/bundler/gems/octopus-263b1b729079/lib/octopus/proxy.rb:254:in `each'
  /usr/local/rvm/gems/ruby-2.7.8/bundler/gems/octopus-263b1b729079/lib/octopus/proxy.rb:254:in `with_each_healthy_shard'
  /usr/local/rvm/gems/ruby-2.7.8/bundler/gems/octopus-263b1b729079/lib/octopus/proxy.rb:175:in `clear_all_connections!'
  /usr/local/rvm/gems/ruby-2.7.8/bundler/gems/octopus-263b1b729079/lib/octopus/model.rb:187:in `clear_all_connections_with_octopus!'
  /usr/local/rvm/gems/ruby-2.7.8/gems/passenger-6.0.14/src/ruby_supportlib/phusion_passenger/loader_shared_helpers.rb:319:in `before_handling_requests'

[calos0921]

I fix the error, to add

active_connection = v.active_connection? rescue false
yield(v) if active_connection

lib/octopus/proxy.rb

  def with_each_healthy_shard
      shards.each do |shard_name, v|
        begin
          active_connection = v.active_connection? rescue false
          yield(v) if active_connection
        rescue => e
          if Octopus.robust_environment?
            Octopus.logger.error "Error on shard #{shard_name}: #{e.message}"