DBD::Proxy man page on HP-UX

Man page or keyword search:  
man Server   10987 pages
apropos Keyword Search (all sections)
Output format
HP-UX logo
[printable version]

DBD::Proxy(3)	      User Contributed Perl Documentation	 DBD::Proxy(3)

       DBD::Proxy - A proxy driver for the DBI

	 use DBI;

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

	 # See the DBI module documentation for full details

       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 con‐
       necting 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 applica‐

       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/discon‐
       nect overhead which is typically much less.  Note that the con‐
       nect_cached method is new and still experimental.

       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 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 DBI 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:


       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 particu‐
	   lar it will contain colons. The dsn value may contain semicolons,
	   hence this key *must* be the last and it's value will be the com‐
	   plete remaining part of the dsn. Example:


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


	   (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 RPC::PlClient. Example:


	   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 userci‐
	   pher/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/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 redi‐
	   rected to stderr.  This is the default under Windows.


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


	   The DBD::Proxy driver supports this attribute (which is DBI stan‐
	   dard, 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 appli‐
	   cation 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 fin‐
	   ish() 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 be‐

	   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).

       Unproxied method calls

       If a method isn't being proxied, try declaring a stub sub in the appro‐
       priate package (DBD::Proxy::db for a dbh method, and DBD::Proxy::st for
       an sth method).	For example:

	   sub DBD::Proxy::db::selectall_arrayref;

       That will enable selectall_arrayref to be proxied.

       Currently many methods aren't explicitly proxied and so you get the
       DBI's default methods executed on the client.

       Some of those methods, like selectall_arrayref, may then call other
       methods that are proxied (selectall_arrayref calls fetchall_arrayref
       which calls fetch which is proxied). So things may appear to work but
       operate more slowly than the could.

       This may all change in a later version.

       Complex handle attributes

       Sometimes handles are having complex attributes like hash refs or array
       refs and not simple strings or integers. For example, with DBD::CSV,
       you would like to write something like

	 $dbh->{"csv_tables"}->{"passwd"} =
	       { "sep_char" => ":", "eol" => "\n";

       The above example would advice the CSV driver to assume the file
       "passwd" to be in the format of the /etc/passwd file: Colons as separa‐
       tors and a line feed without carriage return as line terminator.

       Surprisingly this example doesn't work with the proxy driver. To under‐
       stand the reasons, you should consider the following: The Perl compiler
       is executing the above example in two steps:

       1   The first step is fetching the value of the key "csv_tables" in the
	   handle $dbh. The value returned is complex, a hash ref.

       2   The second step is storing some value (the right hand side of the
	   assignment) as the key "passwd" in the hash ref from step 1.

       This becomes a little bit clearer, if we rewrite the above code:

	 $tables = $dbh->{"csv_tables"};
	 $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\n";

       While the examples work fine without the proxy, the fail due to a sub‐
       tile difference in step 1: By DBI magic, the hash ref
       $dbh->{'csv_tables'} is returned from the server to the client.	The
       client creates a local copy. This local copy is the result of step 1.
       In other words, step 2 modifies a local copy of the hash ref, but not
       the server's hash ref.

       The workaround is storing the modified local copy back to the server:

	 $tables = $dbh->{"csv_tables"};
	 $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\n";
	 $dbh->{"csv_tables"} = $tables;

       This module is Copyright (c) 1997, 1998

	   Jochen Wiedmann
	   Am Eisteich 9
	   72555 Metzingen

	   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.

       DBI, RPC::PlClient, Storable

perl v5.8.8			  2007-05-13			 DBD::Proxy(3)

List of man pages available for HP-UX

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net