Apache HTTP Server Version 2.3
Apache HTTP Server Version 2.3
| Description: | mod_proxy extension for load balancing |
|---|---|
| Status: | Extension |
| Module Identifier: | proxy_balancer_module |
| Source File: | mod_proxy_balancer.c |
| Compatibility: | Available in version 2.1 and later |
This module requires the service of mod_proxy. It provides load balancing support for
HTTP, FTP and AJP13 protocols
Load balancing scheduler algorithm is provided by not this
module but other modules such as:
mod_lbmethod_byrequests,
mod_lbmethod_bytraffic and
mod_lbmethod_bybusyness.
Thus, in order to get the ability of load balancing,
mod_proxy, mod_proxy_balancer
and at least one of load balancing scheduler algorithm modules have
to be present in the server.
Do not enable proxying until you have secured your server. Open proxy servers are dangerous both to your network and to the Internet at large.
Load balancer scheduler algorithm Examples of a balancer configuration Exported Environment Variables Enabling Balancer Manager Support
At present, there are 3 load balancer scheduler algorithms available
for use: Request Counting, Weighted Traffic Counting and Pending Request
Counting. These are controlled via the lbmethod value of
the Balancer definition. See the ProxyPass
directive for more information.
Before we dive into the technical details, here's an example of
how you might use mod_proxy_balancer to provide
load balancing between two back-end servers:
<Proxy balancer://mycluster>
BalancerMember http://192.168.1.50:80
BalancerMember http://192.168.1.51:80
</Proxy>
ProxyPass /test balancer://mycluster
Another example of how to provide load balancing with stickyness
using mod_headers, even if the backend server does
not set a suitable session cookie:
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/"
env=BALANCER_ROUTE_CHANGED
<Proxy balancer://mycluster>
BalancerMember http://192.168.1.50:80 route=1
BalancerMember http://192.168.1.51:80 route=2
ProxySet stickysession=ROUTEID
</Proxy>
ProxyPass /test balancer://mycluster
At present there are 6 environment variables exported:
This is assigned the stickysession value used in the current request. It is the cookie or parameter name used for sticky sessions
This is assigned the route parsed from the current request.
This is assigned the name of the balancer used for the current
request. The value is something like balancer://foo.
This is assigned the name of the worker used for the current request.
The value is something like http://hostA:1234.
This is assigned the route of the worker that will be used for the current request.
This is set to 1 if the session route does not match the worker route (BALANCER_SESSION_ROUTE != BALANCER_WORKER_ROUTE) or the session does not yet have an established route. This can be used to determine when/if the client needs to be sent an updated route when sticky sessions are used.
This module requires the service of
mod_status.
Balancer manager enables dynamic update of balancer
members. You can use balancer manager to change the balance
factor or a particular member, or put it in the off line
mode.
Thus, in order to get the ability of load balancer management,
mod_status and mod_proxy_balancer
have to be present in the server.
To enable load balancer management for browsers from the example.com
domain add this code to your httpd.conf
configuration file
<Location /balancer-manager>
SetHandler balancer-manager
Order Deny,Allow
Deny from all
Allow from .example.com
</Location>
You can now access load balancer manager by using a Web browser
to access the page
http://your.server.name/balancer-manager
| Description: | Set the nonce used in the balancer-manager application |
|---|---|
| Syntax: | BalancerNonce Default|None|Set "value" |
| Default: | ProxyStatus Default |
| Context: | server config, virtual host |
| Status: | Extension |
| Module: | mod_proxy_balancer |
| Compatibility: | Available in version 2.4 and later |
This directive specifies the protective nonce used in the
balancer-manager application page.
The default is to use an automatically determined UUID-based
nonce, to provide for further protection for the page. If set
to Set, then the next argument sets the nonce to that
value. A setting of None disables all nonce checking.
BalancerNonce Set "RealGudSharedSecret"
In addition to the nonce, the balancer-manager page
should be protected via an ACL.