On Apache
Under GNU General Public License
2012-05-19 16:23 @38.107.179.239 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)
Apache::RPC::Status(3pm) User Contributed Perl Documentation Apache::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.
LICENSE
This module and the code within are released under the terms of the Artistic License 2.0
(http://www.opensource.org/licenses/artistic-license-2.0.php). This code may be
redistributed under either the Artistic License or the GNU Lesser General Public License
(LGPL) version 2.1 (http://www.opensource.org/licenses/lgpl-license.php).
SEE ALSO
Apache::Status, Apache::RPC::Server, RPC::XML::Method
AUTHOR
Randy J. Ray <rjray AT blackperl.com>
perl v5.10.0 2008-04-09 Apache::RPC::Status(3pm)
Generated by $Id: phpMan.php,v 4.49 2006/02/26 13:18:18 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2012-05-19 16:23 @38.107.179.239 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)