Module: PG::Connection::Pollable

# File 'lib/pg/connection.rb', line 686

private def polling_loop(poll_meth)
	connect_timeout = conninfo_hash[:connect_timeout]
	if (timeo = connect_timeout.to_i) && timeo > 0
		host_count = (conninfo_hash[:hostaddr].to_s.empty? ? conninfo_hash[:host] : conninfo_hash[:hostaddr]).to_s.count(",") + 1
		stop_time = timeo * host_count + Process.clock_gettime(Process::CLOCK_MONOTONIC)
	end
	iopts = conninfo_hash.compact
	connection_errors = []
	poll_status = PG::PGRES_POLLING_WRITING

	until poll_status == PG::PGRES_POLLING_OK ||
			poll_status == PG::PGRES_POLLING_FAILED

		# Set single timeout to parameter "connect_timeout" but
		# don't exceed total connection time of number-of-hosts * connect_timeout.
		timeout = [timeo, stop_time - Process.clock_gettime(Process::CLOCK_MONOTONIC)].min if stop_time

		hostcnt = remove_current_host(iopts)

		event = if !timeout || timeout >= 0
			# If the socket needs to read, wait 'til it becomes readable to poll again
			case poll_status
			when PG::PGRES_POLLING_READING
				if defined?(IO::READABLE) # ruby-3.0+
					socket_io.wait(IO::READABLE | IO::PRIORITY, timeout)
				else
					IO.select([socket_io], nil, [socket_io], timeout)
				end

			# ...and the same for when the socket needs to write
			when PG::PGRES_POLLING_WRITING
				if defined?(IO::WRITABLE) # ruby-3.0+
					# Use wait instead of wait_readable, since connection errors are delivered as
					# exceptional/priority events on Windows.
					socket_io.wait(IO::WRITABLE | IO::PRIORITY, timeout)
				else
					# io#wait on ruby-2.x doesn't wait for priority, so fallback to IO.select
					IO.select(nil, [socket_io], [socket_io], timeout)
				end
			end
		end

		# connection to server at "localhost" (127.0.0.1), port 5433 failed: timeout expired (PG::ConnectionBad)
		# connection to server on socket "/var/run/postgresql/.s.PGSQL.5433" failed: No such file or directory
		unless event
			connection_errors << (error_message + "timeout expired")
			if hostcnt > 0
				reset_start2(self.class.parse_connect_args(iopts))
				# Restart polling with waiting for writable.
				# Otherwise "not connected" error is raised on Windows.
				poll_status = PG::PGRES_POLLING_WRITING
				next
			else
				finish
				raise PG::ConnectionBad.new(connection_errors.join("\n").b, connection: self)
			end
		end

		# Check to see if it's finished or failed yet
		poll_status = send( poll_meth )
	end

	unless status == PG::CONNECTION_OK
		msg = error_message
		finish
		raise PG::ConnectionBad.new(connection_errors.map{|e| e + "\n" }.join.b + msg, connection: self)
	end
end