Sample 2-tier high availability configuration with Dispatcher, CBR, and Caching Proxy

Set up a 2-tier, high availability configuration that combines the capabilities of two Load Balancer components (the Dispatcher component and the CBR component) along with Caching Proxy.

Server setup

Example of a 2-tier, high availability configuration that uses Dispatcher, CBR, and Caching ProxyHigh availability configuration that uses Dispatcher, CBR, and Caching Proxy
This figure describes the following scenario:
  • EdgeServer1: primary (high availability) Dispatcher machine that is collocated with CBR and Caching Proxy that load balances across web servers
  • EdgeServer2: standby (high availability) Dispatcher machine that is collocated with CBR and Caching Proxy
  • EdgeServer3: CBR and Caching Proxy server
  • WebServerA, WebServerB, WebServerC: backend web servers
The figure shows a basic representation of multiple servers (EdgeServer1, EdgeServer2, EdgeServer3) load balancing across multiple backend web servers. The CBR component uses Caching Proxy to forward requests that are based on the content of the URL to the backend web servers. The Dispatcher component is used to load balance the CBR components across the EdgeServers. The high availability feature of the Dispatcher component is used to ensure that requests to the backend servers continue even if the primary high availability machine (EdgeServer1) fails at any time.

Basic configuration guidelines

  • Configure Caching Proxy to be the same on all the EdgeServers. To improve the overall accessibility to the web pages on the backend servers, set up Caching Proxy to do memory caching. Setting up Caching Proxy enables the EdgeServers to cache web pages that are requested more frequently. For more information about setting up Caching Proxy, refer to the Caching Proxy Administration Guide.
  • Define the cluster address and ports to be the same in both the CBR and Dispatcher components of Load Balancer.
  • Configure the CBR component to be the same across all EdgeServers. Use web servers A, B, and C as your servers on the ports you want to define for the cluster. For more information to configure CBR, read the Configuring Content Based Routing topics.
  • Configure the Dispatcher component to be the same on EdgeServer1 and EdgeServer2. Define all the EdgeServers as your servers on the ports you want to be defined on the cluster to be load balanced by Dispatcher. For more information about how to configure Dispatcher, read the Configuring Dispatcher topics.
  • Configure EdgeServer1 as the primary high availability machine and EdgeServer2 as the standby (backup) high availability machine. For more information, read the High Availability topic.
  1. To avoid backend server addresses displayed in the URL on a client, set the ReversePass directive for each backend server address in the Caching Proxy configuration file.
  2. To ensure that web memory caching is being used effectively, set the Caching directive to ON and increase the CacheMemory directive to the size required in the Caching Proxy configuration file.
  3. Sample lines referred to in steps 1-2:
    Caching              ON
    CacheMemory          128000 K
    ReversePass /* http://websrvA.company.com/* http://www.company.com/*
  4. Alias the cluster address on the network interface card for EdgeServer1 and to alias the cluster address on the loopback device on the remaining EdgeServers.
  5. If using the Linux platform for the EdgeServers, you might install a patch to the Linux kernel or use an alternative to aliasing the loopback device. .
  6. For CBR, do not use port affinity (stickytime) when you use content rules because the content rules do not fire while processing requests to the backend web servers.

Sample configuration files

The following sample configuration files are similar to files that are created when you set up an Edge Components configuration as shown in the figure. The sample configuration files represent the files for the Dispatcher and CBR components of Load Balancer. In the sample configuration, a single Ethernet adapter is used for each of the EdgeServer machines and all addresses are represented within a private subnet. The sample configuration files use the following IP addresses for the specified machines:
  • EdgeServer1 (Primary high availability EdgeServer): 192.168.1.10
  • EdgeServer2 (Backup high availability EdgeServer): 192.168.1.20
  • EdgeServer3 (web caching EdgeServer): 192.168.1.30
  • Website cluster address: 192.168.1.11
  • WebServers A-C (Backend web servers): 192.168.1.71, 192.168.1.72, and 192.168.1.73
Sample configuration file for Dispatcher component on primary high availability EdgeServer
dscontrol executor start

dscontrol cluster add 192.168.1.11 primaryhost 192.168.1.10

dscontrol port add 192.168.1.11@80

dscontrol server add 192.168.1.11@80@edgeserver1 address 192.168.1.10

dscontrol server add 192.168.1.11@80@edgeserver2 address 192.168.1.20

dscontrol server add 192.168.1.11@80@edgeserver3 address 192.168.1.30

dscontrol manager start manager.log 10004

dscontrol highavailability heartbeat add 192.168.1.10 192.168.1.20
dscontrol highavailability backup add primary auto 4567
Sample configuration file for CBR component on the EdgeServers
cbrcontrol set loglevel 1
cbrcontrol executor start

cbrcontrol cluster add 192.168.1.11

cbrcontrol port add 192.168.1.11@80

cbrcontrol server add 192.168.1.11@80@webserverA address 192.168.1.71

cbrcontrol server add 192.168.1.11@80@webserverB address 192.168.1.72

cbrcontrol server add 192.168.1.11@80@webserverC address 192.168.1.73

cbrcontrol rule add 192.168.1.11@80@webA_rule type content 
  pattern (URI=*WSA*)|(URI=*wsA*) priority 21 
cbrcontrol rule useserver 192.168.1.11@80@webA_rule webserverA

cbrcontrol rule add 192.168.1.11@80@webB_rule type content 
  pattern (URI=/WS_B*) priority 22 
cbrcontrol rule useserver 192.168.1.11@80@webB_rule webserverB

cbrcontrol rule add 192.168.1.11@80@webC_rule type content 
  pattern URI=*webC* priority 23 
cbrcontrol rule useserver 192.168.1.21@80@webC_rule webserverC

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Timestamp icon Last updated: March 23, 2018 0:18
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