perlbal::manual::highpriority(3pm) [debian man page]
Perlbal::Manual::HighPriority(3pm) User Contributed Perl Documentation Perlbal::Manual::HighPriority(3pm) NAME
Perlbal::Manual::HighPriority - Perlbal's high/low priority queueing system. VERSION Perlbal 1.78. DESCRIPTION This document describes Perlbal's high/low priority queueing system. Queuing system Perlbal has three queues: normal, high priority and low priority. As their names suggest, this means that usually requests get to the normal queue and are dispatched in FIFO order, with high priority requests going to a different queue that gets ahead of the normal one and a low priority queue that only gets done when the high and normal queues are empty. In a nutshell, whenever Perlbal needs to select which request to take care of next, it first looks for requests in the high priority queue; if that one is empty, it then looks into the normal queue; and, if the normal queue is empty too, it finally looks in the low priority queue. High priority with cookies Perlbal can use cookies to determine if a request should go to the high priority queue (configurable). The parameters to configure this are "high_priority_cookie" and "high_priority_cookie_contents"; the first defines the name of the field to check for on the cookie and the second one defines the content in that field that will trigger the request going to the fast queue: SET myservice.high_priority_cookie = name_of_the_field SET myservice.high_priority_cookie_contents = required_content_on_that_field Here's a clearer example: SET myservice.high_priority_cookie = highpriority SET myservice.high_priority_cookie_contents = yes High priority with plugins The plugin Perlbal::Plugin::Highpri supports making requests high priority by URI or Host. Also check "make_high_priority" under Perlbal::Manual::Hooks. Queue relief Sometimes if the high priority queue is really busy, the standard queue will suffer from resource starvation. The queue relief system helps prevent this. When there are "queue_relief_size" or more connections in the standard queue, newly available backends have a "queue_relief_chance" percent chance of taking a request from the standard priority queue instead of the high priority queue. SET web_proxy.queue_relief_size = 2000 SET web_proxy.queue_relief_chance = 30 # 0-100, in percent SEE ALSO "make_high_priority" and "make_low_priority" in Perlbal::Manual::Hooks, Perlbal::Plugin::HighPriority. perl v5.14.2 2011-01-23 Perlbal::Manual::HighPriority(3pm)
Check Out this Related Man Page
Perlbal::Plugin::Cgilike(3pm) User Contributed Perl Documentation Perlbal::Plugin::Cgilike(3pm) NAME
Perlbal::Plugin::Cgilike - Handle Perlbal requests with a Perl subroutine DESCRIPTION
This module allows responses to be handled with a simple API that's similar in principle to CGI, mod_perl response handlers, etc. It does not, however, come anywhere close to conforming to the CGI "standard". It's actually more like mod_perl in usage, though there are several differences. Most notably, Perlbal is single-process and single-threaded, and handlers run inside the Perlbal process and must therefore return quickly and not do any blocking operations. As it currently stands, this is very bare-bones and has only really been used with basic GET requests. It lacks a nice API for handling the body of a POST or PUT request. It is not recommended to use this for extensive applications. Perlbal is first and foremost a load balancer, so if you're doing something at all complicated you're probably better off using something like Apache mod_perl and then putting Perlbal in front if it if necessary. However, this plugin may prove useful for simple handlers or perhaps embedding a simple HTTP service into another application that uses "Danga::Socket". SYNOPSIS
This module provides a Perlbal plugin which can be loaded and used as follows. LOAD cgilike PERLREQUIRE = MyPackage CREATE SERVICE cgilike SET role = web_server SET listen = 127.0.0.1:80 SET plugins = cgilike PERLHANDLER = MyPackage::handler ENABLE cgilike With this plugin loaded into a particular service, the plugin will then be called for all requests for that service. Set cgilike.handler to the name of a subroutine that will handle requests. This subroutine will receive an object which allows interaction with the Perlbal service. package MyPackage sub handler { my ($r) = @_; if ($r->uri eq '/') { print "<p>Hello, world</p>"; return Perlbal::Plugin::Cgilike::HANDLED; } else { return 404; } } Return "Perlbal::Plugin::Cgilike::HANDLED" to indicate that the request has been handled, or return some HTTP error code to produce a predefined error message. You may also return "Perlbal::Plugin::Cgilike::DECLINED" if you do not wish to handle the request, in which case Perlbal will be allowed to handle the request in whatever way it would have done without Cgilike loaded. If your handler returns any non-success value, it MUST NOT produce any output. If you produce output before returning such a value, the response to the client is likely to be utter nonsense. You may also return "Perlbal::Plugin::Cgilike::POSTPONE_RESPONSE", which is equivalent to returning zero except that the HTTP connection will be left open once you return. It is your responsibility to later call "$r->end_response()" when you have completed the response. This style is necessary when you need to perform some long operation before you can return a response; you'll need to use some appropriate method to set a callback to run when the operation completes and then do your response in the callback. Once you've called "end_response", you must not call any further methods on $r; it's probably safest to just return immediately afterwards to avoid any mishaps. API DOCUMENTATION
TODO: Write this TODO
Currently there is no API for dealing with the body of a POST or PUT request. Ideally it'd be able to do automatic decoding of application/x-www-form-urlencoded data, too. The POSTPONE_RESPONSE functionality has not been tested extensively and is probably buggy. COPYRIGHT AND LICENSE
Copyright 2007 Martin Atkins <mart@degeneration.co.uk> and Six Apart Ltd. This module is part of the Perlbal distribution, and as such can be distributed under the same licence terms as the rest of Perlbal. perl v5.14.2 2010-12-20 Perlbal::Plugin::Cgilike(3pm)