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Apache::RPC::Status(3pUser Contributed Perl DocumentatApache::RPC::Status(3pm)

NAME
       Apache::RPC::Status - A status monitor similar to Apache::Status for
       RPC

SYNOPSIS
	   # In httpd.conf:
	   </Location /rpc-status>
	       SetHandler perl-script
	       PerlHandler Apache::RPC::Status
	   </Location>

	   # In the start-up Perl file:
	   use Apache::RPC::Status;

DESCRIPTION
       The Apache::RPC::Status package is provided as a simple status monitor
       for XML-RPC servers running in a mod_perl environment, using the
       Apache::RPC::Server class (or derivative of). Patterned after the
       status system provided with mod_perl itself, information is broken down
       into a series of screens providing information ranging from the RPC
       servers currently configured down to the individual methods provided by
       the servers.

   Information Screens
       There are three basic screens provided by the stock Apache::RPC::Status
       package:

       Main: Listing of Servers
	   This screen is the first screen that comes up when the location for
	   which this class was assigned as a handler is invoked. It lists the
	   server objects that this running Apache process knows of. Note that
	   if the servers are defined in such a way as to mean on-demand
	   creation, then a given child process may not have all the
	   configured servers in memory. This is by design, it is not a bug.
	   See "Usage Within <Perl> Sections" in Apache::RPC::Server for
	   details on configuring the RPC servers such that they are pre-
	   loaded into all child processes.

       Server: Details of a Server
	   Each of the known servers in the main screen links to this screen,
	   which provides details on the specific server. Information such as
	   when the server was started (which usually matches the time that
	   Apache was started), when the specific child was started (which may
	   not be the same), number of requests servered, and so forth is
	   provided. Additionally, each of the methods that the server
	   provides is listed in alphanumeric order, with a link to the next
	   screen.

       Method: Details of a Specific Method
	   For each of the known methods published by a server, this screen
	   summarizes all that is known about the method itself. The
	   signatures, help text and hidden status (whether the method is
	   visible to the introspection API that is shipped with
	   RPC::XML::Server) are all shown. Some optional information is shown
	   if available: if the method has a version number associated with
	   it, that is displayed. If the method was loaded from an external
	   XPL file, the file path and modification-time are also displayed.

       The primary purpose of this status system is to allow for checking the
       availability and sanity of the RPC servers themselves. For example, if
       a server is configured to auto-load methods, and automatically check
       for updates, the status system could confirm that a method is available
       or is at the correct version.

       (Note that auto-loading and auto-updating are done on demand, when a
       call is made to the method in question. Thus, the status might not
       reflect changes until at least one call has been made. Further, if
       there are very many child processes handling the RPC servers, several
       calls may be necessary to ensure that the child process answering the
       status request also has the most up-to-date impression of the server.)

SUBCLASSING AND EXTENDING
       This package is implemented as a method handler for Apache/mod_perl.
       This means that is should be relatively easy to subclass this package
       to implement an extended version of status reporting, or to provide
       handlers for phases of the request lifecycle not otherwise addressed.

   Class Methods
       There are three class methods defined in this package. One is the
       constructor, the other two are handlers for specific phases in the
       Apache request lifecycle.

       new(CLASS, ARGS)
	   This creates a new object of this class and returns a reference to
	   it. The first argument is the class being created into, the
	   remaining arguments are treated as key/value pairs (note: not a
	   hash reference). At present, the only additional argument
	   recognized is:

	   serverclass
		   This is used when the status monitor is being used with a
		   server class other than Apache::RPC::Server directly.
		   Because several methods from that class are invoked, it is
		   presumed that the class named here is a subclass of
		   Apache::RPC::Server. If not, the status monitor may not
		   work correctly, or at all. In the absence of this value,
		   "Apache::RPC::Server" is assumed. This value may also be
		   set with the mod_perl PerlSetVar directive. See the
		   documentation for "init_handler", below.

       handler(CLASS, REQUEST)
	   This is the primary entry-point for the package. This is the
	   handler defined for assignment to "PerlHandler" in a location
	   configuration block. It is invoked by mod_perl as a method handler,
	   thus the first argument is either the name of the class (in the
	   case of class-method, or static, invocation) or the object
	   configured as the handler. The second argument is the Apache
	   request object itself.

	   This method derives the query parameters for the request from the
	   Apache object, and treats them according to the type of information
	   screen requested:

	   screen  This specifies which screen of the status monitor is to be
		   displayed. In absence, the value defaults to "main", which
		   is the internal identifier for the primary screen of the
		   status monitor system. If the value of this parameter does
		   not match a known interface hook, then the handler will
		   signify to mod_perl that it cannot handler the request, by
		   replying with the "DECLINED" response code.

	   server  When the screen parameter is set to "server", the monitor
		   displays the server detail screen. In that case, this
		   parameter specifies which server should be displayed.
		   Servers are given unique identifiers when they are created,
		   usually derived from the URL path that they are attached
		   to. If the value here does not match any known servers, a
		   warning is sent to the browser.

	   method  When the screen parameter is set to "method", this calls
		   for the method detail screen. The provided interface hook
		   to deal with these requests looks for both the server
		   parameter above and this one, which specifies by name the
		   method to be laid out in detail. As with the server
		   parameter, if the value in this parameter does not match
		   any known data, an error is reported to the browser.

	   Any additional parameters will be preserved by make_url call
	   detailed below. These are merely the specific ones recognized by
	   the status monitor as written.

       init_handler(CLASS, REQUEST)
	   This is a very simple handler designed for the PerlChildInitHandler
	   phase. At present, it only does one simple task (and thus makes no
	   direct use of either parameter passed to it by mod_perl). However,
	   it is included mainly as a placeholder for possible future
	   expansion. The current behavior is to check for the existence of
	   directory-configuration item called "ServerClass", and record the
	   value if it is set. This is used to specifiy the class from which
	   the RPC server objects are created, if something other than
	   Apache::RPC::Server. If this information is passed via the
	   "serverclass" parameter to the new method above, that value
	   overrides any value here. However, that requires actually creating
	   an object to use as the handler, whereas this handler may be used
	   directly, as a static handler. It would be configured outside of
	   any <Location> blocks, a requirement for the PerlChildInitHandler
	   phase. It is designed to stack cleanly with any other handlers for
	   that phase, provided your mod_perl installation supports stacked
	   handlers.

   Additional Methods
       In addition to the class methods above, the following are provided. In
       most cases, these do not rely on any data contained within the actual
       object itself. Many may also be called as static methods (these are so
       noted). They are provided as a utility, implemented as methods so as to
       avoid namespace issues:

       version
	   (May be called as a static method.) Returns the current version of
	   this module.

       apache_status_attach
	   Attach the Apache::RPC::Status module to the main screen of the
	   Apache::Status display.

       default_object
	   (May be called as a static method.) Returns a default
	   Apache::RPC::Status instance when called as a static method.
	   Returns the calling reference itself, otherwise.

       header(REQUEST, TITLE)
	   Produces the HTML header for a page. Uses the passed-in title
	   parameter to give the page a title, and extracts any request-
	   specific information from the Apache request object passed as the
	   first parameter.

       footer(REQUEST)
	   Produces the HTML footer.

       make_url(QUERY|REQUEST, FLAG)
	   (May be called as a static method.) This creates a URL string for
	   use as a hyperlink. It makes certain to preserve all parameters in
	   a CGI-like fashion. Additionally, it can make the URL in such a
	   fashion as to allow better integration with the Apache::Status
	   package. If the "FLAG" parameter is passed and is any true value,
	   then the resulting URL will be tailored for use with
	   Apache::Status. The first argument must be either the original
	   request object as passed by mod_perl, or a reference to a CGI
	   object created from the request (see CGI for more on the CGI
	   class).

       main_screen(REQUEST, QUERY, INTERNAL)
	   Renders the HTML (minus the header and footer) for the main screen.
	   The arguments are the Apache request object, a CGI query object
	   created from the request, and a boolean flag indicating whether the
	   call into this method was made from within this module or made from
	   the Apache::Status page.

       server_summary(SERVER)
	   Creates an HTML snippet to provide a summary for the server passed
	   in as an argument. The passed-in value should be the server object,
	   not the name.

       server_detail(REQUEST, QUERY, INTERNAL)
	   Renders the HTML (minus header and footer) for a screen describing
	   a server instance in detail. The server is specified by name in the
	   query parameters.  The arguments are the same as for "main_screen".

       method_summary(SERVER, METHOD, BASEURL)
	   Creates and HTML snippet to provide a summary for the specified
	   method of the specified server. The third argument is a base-URL to
	   use for making links to the detailed method page.

       method_detail(REQUEST, QUERY, INTERNAL)
	   Renders the HTML (minus header and footer) for a screen describing
	   a method on a specific server instance, in detail. The method and
	   server are specified by name in the query parameters. The arguments
	   are the same as for "main_screen".

   Use and Extension Within Perl Sections
       Some extension may be done without necessarily subclassing this
       package. The class object are implemented simply as hash references.
       When a request is received, the screen parameter (see above) is
       extracted, and used to look up in the hash table. If there is a value
       for that key, the value is assumed to be a hash reference with at least
       two keys (described below). If it does not exist, the handler routine
       declines to handle the request. Thus, some degree of extension may be
       done without the need for developing a new class, if the configuration
       and manipulation are done within <Perl> configuration blocks.

       Adding a new screen means writing a routine to handle the requests, and
       then adding a hook into that routine to the object that is the handler
       for the Apache location that serves RPC status requests. The routines
       that are written to handle a request should expect four arguments (in
       order):

       The object reference for the location handler
       The Apache request object reference
       A query object reference (see below)
       A flag that is only passed when called from Apache::Status

       The routines are given both the original request object and a query
       object reference for sake of ease. The query object is already
       available prior to the dispatch, so there is no reason to have each
       hook routine write the same few lines to derive a query object from an
       Apache request. At the same time, the hooks themselves may need the
       Apache object to call methods on. The query object is an instance of
       CGI. The flag parameter is passed by the linkage from this status
       package to Apache::Status. The primary use for it is to pass to
       routines such as make_url that are sensitive to the Apache::Status
       context.

       The return value from these routines must be a reference to a list of
       lines of text. It is passed to the print method of the Apache class.
       This is necessary for compatibility with the Apache::Status
       environment.

       To add a new hook, merely assign it to the object directly. The key is
       the value of the "screen" parameter defined above, and the value is a
       hash reference with two keys:

       title
	   A string that is incorporated into the HTML title for the page.

       call
	   A reference to a subroutine or closure that implements the hook,
	   and conforms to the conventions described above.

       A sample addition:

	   $stat_obj->{dbi} = {
				  title => 'RPC-side DBI Pool',
				  call	=> \&show_dbi_pool
			      };

INTEGRATION WITH Apache::Status
       This package is designed to integrate with the Apache::Status package
       that is a part of mod_perl. However, this is not currently functional.
       When this has been debugged, the details will be presented here.

CAVEATS
       This is the newest part of the RPC-XML package. While the package as a
       whole is now considered beta, this piece may yet undergo some alpha-
       like enhancements to the interface and such. However, the design and
       planning of this were carefully considered, so any such changes should
       be minimal.

BUGS
       Please report any bugs or feature requests to "bug-rpc-xml at
       rt.cpan.org", or through the web interface at
       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=RPC-XML>. I will be
       notified, and then you'll automatically be notified of progress on your
       bug as I make changes.

SUPPORT
       ·   RT: CPAN's request tracker

	   <http://rt.cpan.org/NoAuth/Bugs.html?Dist=RPC-XML>

       ·   AnnoCPAN: Annotated CPAN documentation

	   <http://annocpan.org/dist/RPC-XML>

       ·   CPAN Ratings

	   <http://cpanratings.perl.org/d/RPC-XML>

       ·   Search CPAN

	   <http://search.cpan.org/dist/RPC-XML>

       ·   Source code on GitHub

	   <http://github.com/rjray/rpc-xml>

COPYRIGHT & LICENSE
       This file and the code within are copyright (c) 2009 by Randy J. Ray.

       Copying and distribution are permitted under the terms of the Artistic
       License 2.0
       (<http://www.opensource.org/licenses/artistic-license-2.0.php>) or the
       GNU LGPL 2.1 (<http://www.opensource.org/licenses/lgpl-2.1.php>).

CREDITS
       The XML-RPC standard is Copyright (c) 1998-2001, UserLand Software,
       Inc.  See <http://www.xmlrpc.com> for more information about the XML-
       RPC specification.

SEE ALSO
       Apache::Status, Apache::RPC::Server, RPC::XML::Method

AUTHOR
       Randy J. Ray <rjray@blackperl.com>

perl v5.10.0			  2009-12-07	      Apache::RPC::Status(3pm)
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