module PG::Connection::Pollable

Private Instance Methods

polling_loop(poll_meth) click to toggle source

Track the progress of the connection, waiting for the socket to become readable/writable before polling it.

Connecting to multiple hosts is done like so:

All hosts are passed to PG::Connection.connect_start
As soon as the host is tried to connect the related host is removed from the hosts list
When the polling status changes to ‘PG::PGRES_POLLING_OK` the connection is returned and ready to use.
When the polling status changes to ‘PG::PGRES_POLLING_FAILED` connecting is aborted and a PG::ConnectionBad is raised with details to all connection attepts.
When a timeout occurs, connecting is restarted with the remaining hosts.

The downside is that this connects only once to hosts which are listed twice when they timeout.

# File lib/pg/connection.rb, line 685
        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

remove_current_host(iopts) click to toggle source

Remove the host to which the connection is currently established from the option hash. Affected options are:

:host
:hostaddr
:port

Return the number of remaining hosts.

# File lib/pg/connection.rb, line 761
        def remove_current_host(iopts)
        ihosts = iopts[:host]&.split(",", -1)
        ihostaddrs = iopts[:hostaddr]&.split(",", -1)
        iports = iopts[:port]&.split(",", -1)
        iports = iports * (ihosts || ihostaddrs || [1]).size if iports&.size == 1

        idx = (ihosts || ihostaddrs || iports).index.with_index do |_, i|
                (ihosts ? ihosts[i] == host : true) &&
                (ihostaddrs && respond_to?(:hostaddr, true) ? ihostaddrs[i] == hostaddr : true) &&
                (iports ? iports[i].to_i == port : true)
        end

        if idx
                ihosts&.delete_at(idx)
                ihostaddrs&.delete_at(idx)
                iports&.delete_at(idx)

                iopts.merge!(
                        host: ihosts.join(",")) if ihosts
                iopts.merge!(
                        hostaddr: ihostaddrs.join(",")) if ihostaddrs
                iopts.merge!(
                        port: iports.join(",")) if iports
        end

        (ihosts || ihostaddrs || iports).size
end