Perlbal::Manual::Roles(3pm) User Contributed Perl Documentation Perlbal::Manual::Roles(3pm)NAME
Perlbal::Manual::Roles - Roles supported by Perlbal
VERSION
Perlbal 1.78.
DESCRIPTION
Brief description of Perlbal's roles.
Available Roles
management
Used to set a management service (a port you can telnet to and issue configuration/debugging commands to).
See Perlbal::Manual::Management for more information.
reverse_proxy
Used for reverse proxy and load balancing.
See Perlbal::Manual::LoadBalancer and Perlbal::Manual::ReverseProxy for more information.
selector
A virtual service that maps onto other services.
See Perlbal::Manual::Selector for more information.
web_server
Used to set Perlbal as a web server.
See Perlbal::Manual::WebServer for more information.
SEE ALSO
Perlbal::Manual::LoadBalancer, Perlbal::Manual::Management, Perlbal::Manual::ReverseProxy, Perlbal::Manual::Selector,
Perlbal::Manual::WebServer.
perl v5.14.2 2011-01-23 Perlbal::Manual::Roles(3pm)
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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)