NAME

DBD::Proxy - A proxy driver for the DBI

SYNOPSIS

use DBI;

$dbh = DBI->connect("dbi:Proxy:hostname=$host;port=$port;dsn=$db",
                    $user, $passwd);

# See the DBI module documentation for full details

DESCRIPTION

DBD::Proxy is a Perl module for connecting to a database via a remote DBI driver. This is of course not needed for DBI drivers which already support connecting to a remote database, but there are engines which don't offer network connectivity. Another application is offering database access through a firewall, as the driver offers query based restrictions. For example you can restrict queries to exactly those that are used in a given CGI application.

CONNECTING TO THE DATABASE

Before connecting to a remote database, you must ensure, that a Proxy server is running on the remote machine. There's no default port, so you have to ask your system administrator for the port number. See DBI::ProxyServer(3) for details.

Say, your Proxy server is running on machine "alpha", port 3334, and you'd like to connect to an ODBC database called "mydb" as user "joe" with password "hello". When using DBD::ODBC directly, you'd do a

$dbh = DBI->connect("DBI:ODBC:mydb", "joe", "hello");

With DBD::Proxy this becomes

$dsn = "DBI:Proxy:hostname=alpha;port=3334;dsn=DBI:ODBC:mydb";
$dbh = DBI->connect($dsn, "joe", "hello");

You see, this is mainly the same. The DBD::Proxy module will create a connection to the Proxy server on "alpha" which in turn will connect to the ODBC database.

DBD::Proxy's DSN string has the format

$dsn = "DBI:Proxy:key1=val1; ... ;keyN=valN;dsn=valDSN";

In other words, it is a collection of key/value pairs. The following keys are recognized:

hostname

port

Hostname and port of the Proxy server; these keys must be present, no defaults. Example:

hostname=alpha;port=3334

dsn

The value of this attribute will be used as a dsn name by the Proxy server. Thus it must have the format DBI:driver:..., in particular it will contain colons. The dsn value may contain semicolons, hence this key *must* be the last and it's value will be the complete remaining part of the dsn. Example:

dsn=DBI:ODBC:mydb

cipher

key

usercipher

userkey

By using these fields you can enable encryption. If you set, for example,

cipher=$class:key=$key

then DBD::Proxy will create a new cipher object by executing

$cipherRef = $class->new(pack("H*", $key));

and pass this object to the RPC::pClient module when creating a client. See RPC::pClient(3). Example:

cipher=IDEA:key=97cd2375efa329aceef2098babdc9721

The usercipher/userkey attributes allow you to use two phase encryption: The cipher/key encryption will be used in the login and authorisation phase. Once the client is authorised, he will change to usercipher/userkey encryption. Thus the cipher/key pair is a host based secret, typically less secure than the usercipher/userkey secret and readable by anyone. The usercipher/userkey secret is your private secret.

Of course encryption requires an appropriately configured server. See <DBD::ProxyServer(3)/CONFIGURATION FILE>.

debug

Turn on debugging mode

proxy_cache_rows

The DBI supports only fetching one or all rows at a time. This is not appropriate for an application using DBD::Proxy, as one network packet per result column may slow down things drastically.

Thus the driver is usually fetching a certain number of rows via the network and caches it for you. By default the value 20 is used, but you can override it with the proxy_cache_rows attribute. This is a database handle attribute, but it is inherited and overridable for the statement handles: Say, you have a table with large blobs, then you might prefer something like this:

$sth->prepare("SELECT * FROM images");
$sth->{'proxy_cache_rows'} = 1;            # Disable caching

proxy_no_finish

This attribute is another attempt to reduce network traffic: If the application is calling $sth->finish() or destroys the statement handle, then the proxy tells the server to finish or destroy the remote statement handle. Of course this slows down things quite a lot, but is prefectly well for avoiding memory leaks with persistent connections.

However, if you set the proxy_no_finish attribute to a TRUE value, either in the database handle or in the statement handle, then the finish() or DESTROY() calls will be supressed. This is what you want, for example, in small and fast CGI applications.

AUTHOR AND COPYRIGHT

This module is Copyright (c) 1997, 1998

Jochen Wiedmann
Am Eisteich 9
72555 Metzingen
Germany

Email: joe@ispsoft.de
Phone: +49 7123 14887

The DBD::Proxy module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. In particular permission is granted to Tim Bunce for distributing this as a part of the DBI.

SEE ALSO

DBI(3), RPC::pClient(3), Storable(3)