lib::DBD::Proxy(3)

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.

Speaking of CGI, another application is (or rather, will be) to reduce the database connect/disconnect overhead from CGI scripts by using proxying the connect_cached method. The proxy server will hold the database connections open in a cache. The CGI script then trades the database connect/disconnect overhead for the DBD::Proxy connect/disconnect overhead which is typically much less. Note that the connect_cached method is new and still experimental.

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 the DBI::ProxyServer(3) manpage 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.

Refer to the the DBI(3) manpage documentation on the connect method for a way to automatically use DBD::Proxy without having to change your code.

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

    hostname=alpha;port=3334
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
By using these fields you can enable encryption. If you set, for example,

    cipher=$class;key=$key
(note the semicolon) then DBD::Proxy will create a new cipher object by executing

    $cipherRef = $class->new(pack("H*", $key));
and pass this object to the RPC::PlClient module when creating a client. See the RPC::PlClient(3) manpage. 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>. Turn on debugging mode This attribute will set the corresponding attribute of the RPC::PlClient object, thus logging will not use syslog(), but redirected to stderr. This is the default under Windows.

    stderr=1
Similar to the stderr attribute, but output will be redirected to the given file.

    logfile=/dev/null
The DBD::Proxy driver supports this attribute (which is DBI standard, as of DBI 1.02). It's used to reduce network round-trips by fetching multiple rows in one go. The current default value is 20, but this may change. This attribute can be used to reduce network traffic: If the application is calling $sth->finish() then the proxy tells the server to finish the remote statement handle. Of course this slows down things quite a lot, but is prefectly good for reducing memory usage 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 finish() calls will be supressed. This is what you want, for example, in small and fast CGI applications. This attribute can be used to reduce network traffic: By default calls to $dbh->quote() are passed to the remote driver. Of course this slows down things quite a lot, but is the safest default behaviour.

However, if you set the proxy_quote attribute to the value 'local' either in the database handle or in the statement handle, and the call to quote has only one parameter, then the local default DBI quote method will be used (which will be faster but may be wrong).

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
the DBI(3) manpage, the RPC::PlClient(3) manpage, the Storable(3) manpage