gofer.pm

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

        }
        # set error/warn/info (after more_results as that'll clear err)
        DBD::Gofer::set_err_from_response($sth, $response);

        return $response->rv;
    }


    sub bind_param {
        my ($sth, $param, $value, $attr) = @_;
        $sth->{ParamValues}{$param} = $value;
        $sth->{ParamAttr}{$param}   = $attr
            if defined $attr; # attr is sticky if not explicitly set
        return 1;
    }


    sub execute {
        my $sth = shift;
        $sth->bind_param($_, $_[$_-1]) for (1..@_);
        push @{ $sth->{go_method_calls} }, [ 'execute' ];
        my $meta = { go_last_insert_id_args => $sth->{go_last_insert_id_args} };
        return $sth->go_sth_method($meta);
    }


    sub more_results {
        my $sth = shift;

        $sth->finish;

        my $response = $sth->{go_response} or do {
            # e.g., we haven't sent a request yet (ie prepare then more_results)
            $sth->trace_msg("    No response object present", 3);
            return;
        };

        my $resultset_list = $response->sth_resultsets
            or return $sth->set_err($DBI::stderr, "No sth_resultsets");

        my $meta = shift @$resultset_list
            or return undef; # no more result sets
        #warn "more_results: ".Data::Dumper::Dumper($meta);

        # pull out the special non-atributes first
        my ($rowset, $err, $errstr, $state)
            = delete @{$meta}{qw(rowset err errstr state)};

        # copy meta attributes into attribute cache
        my $NUM_OF_FIELDS = delete $meta->{NUM_OF_FIELDS};
        $sth->STORE('NUM_OF_FIELDS', $NUM_OF_FIELDS);
        # XXX need to use STORE for some?
        $sth->{$_} = $meta->{$_} for keys %$meta;

        if (($NUM_OF_FIELDS||0) > 0) {
            $sth->{go_rows}           = ($rowset) ? @$rowset : -1;
            $sth->{go_current_rowset} = $rowset;
            $sth->{go_current_rowset_err} = [ $err, $errstr, $state ]
                if defined $err;
            $sth->STORE(Active => 1) if $rowset;
        }

        return $sth;
    }


    sub go_clone_sth {
        my ($sth1) = @_;
        # clone an (un-fetched-from) sth - effectively undoes the initial more_results
        # not 100% so just for use in caching returned sth e.g. table_info
        my $sth2 = $sth1->{Database}->prepare($sth1->{Statement}, { go_skip_prepare_check => 1 });
        $sth2->STORE($_, $sth1->{$_}) for qw(NUM_OF_FIELDS Active);
        my $sth2_inner = tied %$sth2;
        $sth2_inner->{$_} = $sth1->{$_} for qw(NUM_OF_PARAMS FetchHashKeyName);
        die "not fully implemented yet";
        return $sth2;
    }


    sub fetchrow_arrayref {
        my ($sth) = @_;
        my $resultset = $sth->{go_current_rowset} || do {
            # should only happen if fetch called after execute failed
            my $rowset_err = $sth->{go_current_rowset_err}
                || [ 1, 'no result set (did execute fail)' ];
            return $sth->set_err( @$rowset_err );
        };
        return $sth->_set_fbav(shift @$resultset) if @$resultset;
        $sth->finish;     # no more data so finish
        return undef;
    }
    *fetch = \&fetchrow_arrayref; # alias


    sub fetchall_arrayref {
        my ($sth, $slice, $max_rows) = @_;
        my $resultset = $sth->{go_current_rowset} || do {
            # should only happen if fetch called after execute failed
            my $rowset_err = $sth->{go_current_rowset_err}
                || [ 1, 'no result set (did execute fail)' ];
            return $sth->set_err( @$rowset_err );
        };
        my $mode = ref($slice) || 'ARRAY';
        return $sth->SUPER::fetchall_arrayref($slice, $max_rows)
            if ref($slice) or defined $max_rows;
        $sth->finish;     # no more data after this so finish
        return $resultset;
    }


    sub rows {
        return shift->{go_rows};
    }


    sub STORE {
        my ($sth, $attrib, $value) = @_;

        return $sth->SUPER::STORE($attrib => $value)
            if $sth_local_store_attrib{$attrib} # handle locally
            # or it's a private_ (application) attribute
            or $attrib =~ /^private_/;

        # otherwise warn but do it anyway
        # this will probably need refining later
        my $msg = "Altering \$sth->{$attrib} won't affect proxied handle";
        Carp::carp($msg) if $sth->FETCH('Warn');

        # XXX could perhaps do
        #   push @{ $sth->{go_method_calls} }, [ 'STORE', $attrib, $value ]
        #       if not $sth->FETCH('Executed');
        # but how to handle repeat executions? How to we know when an
        # attribute is being set to affect the current resultset or the
        # next execution?
        # Could just always use go_method_calls I guess.

        # do the store locally anyway, just in case
        $sth->SUPER::STORE($attrib => $value);

        return $sth->set_err($DBI::stderr, $msg);
    }

    # sub bind_param_array
    # we use DBI's default, which sets $sth->{ParamArrays}{$param} = $value
    # and calls bind_param($param, undef, $attr) if $attr.

    sub execute_array {
        my $sth = shift;
        my $attr = shift;
        $sth->bind_param_array($_, $_[$_-1]) for (1..@_);
        push @{ $sth->{go_method_calls} }, [ 'execute_array', $attr ];
        return $sth->go_sth_method($attr);
    }

    *go_cache = \&DBD::Gofer::go_cache;
}

1;

__END__

=head1 NAME

DBD::Gofer - A stateless-proxy driver for communicating with a remote DBI

=head1 SYNOPSIS

  use DBI;

  $original_dsn = "dbi:..."; # your original DBI Data Source Name

  $dbh = DBI->connect("dbi:Gofer:transport=$transport;...;dsn=$original_dsn",
                      $user, $passwd, \%attributes);

  ... use $dbh as if it was connected to $original_dsn ...


The C<transport=$transport> part specifies the name of the module to use to
transport the requests to the remote DBI. If $transport doesn't contain any
double colons then it's prefixed with C<DBD::Gofer::Transport::>.

The C<dsn=$original_dsn> part I<must be the last element> of the DSN because
everything after C<dsn=> is assumed to be the DSN that the remote DBI should
use.

The C<...> represents attributes that influence the operation of the Gofer
driver or transport. These are described below or in the documentation of the
transport module being used.

=head1 DESCRIPTION

DBD::Gofer is a DBI database driver that forwards requests to another DBI
driver, usually in a seperate process, often on a separate machine. It tries to
be as transparent as possible so it appears that you are using the remote
driver directly.

DBD::Gofer is very similar to DBD::Proxy. The major difference is that with
DBD::Gofer no state is maintained on the remote end. That means every
request contains all the information needed to create the required state. (So,
for example, every request includes the DSN to connect to.) Each request can be
sent to any available server. The server executes the request and returns a
single response that includes all the data.

This is very similar to the way http works as a stateless protocol for the web.
Each request from your web browser can be handled by a different web server process.

=head2 Use Cases

This may seem like pointless overhead but there are situations where this is a
very good thing. Let's consider a specific case.

Imagine using DBD::Gofer with an http transport. Your application calls
connect(), prepare("select * from table where foo=?"), bind_param(), and execute().
At this point DBD::Gofer builds a request containing all the information
about the method calls. It then uses the httpd transport to send that request
to an apache web server.

This 'dbi execute' web server executes the request (using DBI::Gofer::Execute
and related modules) and builds a response that contains all the rows of data,
if the statement returned any, along with all the attributes that describe the
results, such as $sth->{NAME}. This response is sent back to DBD::Gofer which
unpacks it and presents it to the application as if it had executed the
statement itself.

=head2 Advantages

Okay, but you still don't see the point? Well let's consider what we've gained:

=head3 Connection Pooling and Throttling

The 'dbi execute' web server leverages all the functionality of web
infrastructure in terms of load balancing, high-availability, firewalls, access
management, proxying, caching.

At its most basic level you get a configurable pool of persistent database connections.

=head3 Simple Scaling

Got thousands of processes all trying to connect to the database? You can use
DBD::Gofer to connect them to your smaller pool of 'dbi execute' web servers instead.

=head3 Caching

Client-side caching is as simple as adding "C<cache=1>" to the DSN.
This feature alone can be worth using DBD::Gofer for.

=head3 Fewer Network Round-trips

DBD::Gofer sends as few requests as possible (dependent on the policy being used).

=head3 Thin Clients / Unsupported Platforms

You no longer need drivers for your database on every system.  DBD::Gofer is pure perl.

=head1 CONSTRAINTS

There are some natural constraints imposed by the DBD::Gofer 'stateless' approach.
But not many:

=head2 You can't change database handle attributes after connect()

You can't change database handle attributes after you've connected.
Use the connect() call to specify all the attribute settings you want.

This is because it's critical that when a request is complete the database
handle is left in the same state it was when first connected.

An exception is made for attributes with names starting "C<private_>":
They can be set after connect() but the change is only applied locally.

=head2 You can't change statement handle attributes after prepare()

You can't change statment handle attributes after prepare.

An exception is made for attributes with names starting "C<private_>":
They can be set after prepare() but the change is only applied locally.

=head2 You can't use transactions

AutoCommit only. Transactions aren't supported.

(In theory transactions could be supported when using a transport that
maintains a connection, like C<stream> does. If you're interested in this
please get in touch via [e-mail])

=head2 You can't call driver-private sth methods

But that's rarely needed anyway.

=head1 GENERAL CAVEATS

A few important things to keep in mind when using DBD::Gofer:

=head2 Temporary tables, locks, and other per-connection persistent state

You shouldn't expect any per-session state to persist between requests.
This includes locks and temporary tables.

Because the server-side may execute your requests via a different
database connections, you can't rely on any per-connection persistent state,
such as temporary tables, being available from one request to the next.

This is an easy trap to fall into. A good way to check for this is to test your
code with a Gofer policy package that sets the C<connect_method> policy to
'connect' to force a new connection for each request. The C<pedantic> policy does this.

=head2 Driver-private Database Handle Attributes

Some driver-private dbh attributes may not be available if the driver has not
implemented the private_attribute_info() method (added in DBI 1.54).

=head2 Driver-private Statement Handle Attributes

Driver-private sth attributes can be set in the prepare() call. TODO

Some driver-private dbh attributes may not be available if the driver has not
implemented the private_attribute_info() method (added in DBI 1.54).

=head2 Multiple Resultsets