MySQL client is not connected

[kuldeepaggarwal]

Hi team, during the testing I found a very unusual behaviour of Toxiproxy#down method. The following snippet causes the MySQL client is not connected error:

test "#record_create throws a SQL exception if mysql_master database is down" do
  record = Record.new(attributes)
  Toxiproxy[:mysql_master].down do
    assert_raises(ActiveRecord::ConnectionNotEstablished, ActiveRecord::StatementInvalid) do
       create_record(record)
    end
  end
  Record.first # => raising an error, i.e. "ActiveRecord::ConnectionNotEstablished: MySQL client is not connected"
end

[miry]

@kuldeepaggarwal can you provide your expectations?

[DougEdey]

@kuldeepaggarwal the issue is that ActiveRecord caches the connection, after you've taken down the DB and run a query it breaks the connection that's cached, you need to do an ActiveRecord::Base.connection.reset! (or there's probably a better equivalent) to reset the cached connection.

I've got a ToxiproxyHelper module in my apps that sets this up as a teardown:

 def self.included(base)
    return unless base.ancestors.include?(ActiveSupport::TestCase)

    base.class_eval do
      teardown do
        Toxiproxy.reset
        # Rails caches the connection which we may have broken
        ActiveRecord::Base.connection.reset!
      end
    end
  end