Pinging a closed connection shouldn't be considered a failure

[casperisfine]

When reconnecting, Active Record's MySQL2Adapter closes the old connection, but keep the old connection around:

      def active?
        !!@raw_connection&.ping
      end
# ....
        def connect
          @raw_connection = self.class.new_client(@connection_parameters)
        end

        def reconnect
          @raw_connection&.close
          connect
        end

So if that reconnection attempts fail, we are left with a closed connection in @raw_connection.

The problem is that if the circuit breaker was open, before closing again we move to half-open state, meaning we open again on the first failure.

Since before reconnecting Mysql2Adapter does try to ping the existing connection, we end up reopening the CB immediately because we called ping on a closed connection.

Either way it makes no sense to report a failure in such case, as a closed connection is no indication of a resource having a problem.

@bmansoob @eileencodes @miry

[miry]

Tested successfully in shopstatus.

[miry]

Suggested change

	assert_equal(false, client.ping)
	refute(client.ping)

[casperisfine]

Hum, I changed it, but I totally disagree with that code, refute check for falsey, not just false. I meant to make sure it was false not just nil.

But whatever.

[miry]

Feel free to disable this cop.

I am also don't prefer to use refute.