11 Configuring a Hierarchy of Caches

This section describes additional configuration options available for cache hierarchy deployments. This section contains the following topics:

• Configuring a Distributed Cache Hierarchy

• Configuring an ESI Cache Hierarchy

• Additional Hierarchy Configuration for a Cache Cluster

  
  

  See Also: "Cache Hierarchies" for an overview of cache hierarchies "Compression" for a description of how compression works in a cache hierarchies

  
  

Configuring a Distributed Cache Hierarchy

In a distributed cache hierarchy, the central cache stores content from application Web servers, and the remote cache stores content from the central cache. In other words, the central cache acts as an origin server to the remote cache.

To configure a distributed cache hierarchy, perform the tasks in "Tasks for Setting Up OracleAS Web Cache" for each cache. When performing the tasks, take special care to perform the following:

1. Configure the correct origin server:

   • For the central cache, configure the central origin servers from the Origin Servers page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Application > Origin Servers) or OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Origin Servers).

   • For the remote caches, configure the central cache as the origin server in the Origin Server page.

2. Create the same site definition for both the central and remote caches from the Sites page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Application > Sites) or the Site Definitions page of OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Site Definitions).

3. For both central and remote caches, map the site definition to the origin server (configured in Step 0) from the Sites page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Application > Sites) or the Site-to-Server Mapping page of OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Site-to-Server Mapping):

   • For the central cache, map the site to the application Web server or proxy server.

   • For the remote cache, map the site to the central cache.

4. Route that network so that client browser requests are forwarded to the nearest cache.

5. Optionally, ensure that the ClientIP address information that is forwarded to the cache and origin server is valid.

   
   

   See Also: "Ensuring That ClientIP Headers Are Valid"

   
   

When content from the central cache becomes invalid, an invalidation message is sent to its cache. In addition, the central cache propagates the invalidation message to the remote caches.

Note: For automatic propagation of invalidation messages, OracleAS Web Cache passes the encoded invalidator password in the page request between the remote and central cache during the hierarchy registration process. This HTTP traffic is susceptible to network sniffing. If the network is unprotected and insecure, configure HTTPS ports as follows: In the Ports page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Web Cache > Ports) or the Listen Ports page of OracleAS Web Cache Manager (Ports > Listen Ports) of the central cache, disable the default HTTP port and configure an HTTPS port in its place. In the Ports page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Web Cache > Ports) or the Operations Ports page of OracleAS Web Cache Manager (Ports > Operations Ports) of the remote cache, disable the default HTTP port for invalidation and configure an HTTPS port in its place.

Table 11-1 shows the example settings for the deployment depicted in "Deploying a Distributed Cache Hierarchy".

Table 11-1 Settings for us.webche-host and jp.webche-host

Central Cache us.webche1-host and us.webche2-host	Remote Cache jp.webche-host	Setting Location in Oracle Enterprise Manager 10g Application Server Control Console and OracleAS Web Cache Manager
Port: 7777	Port: 7777	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Web Cache > Ports OracleAS Web Cache Manager: Ports > Listen Ports
Host and Port: app1-host1: 7778 Host and Port: app1-host2: 7778 Host and Port: app2-host: 7778	Host and Port: us.webche1-host: 7777 Host and Port: us.webche2-host: 7777	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Origin Servers OracleAS Web Cache Manager: Origin Servers, Sites, and Load Balancing > Origin Servers
Host and Port: www.app1.company.com:80 Host and Port: www.app2.company.com:80	Host and Port: www.app1.company.com:80 Host and Port: www.app2.company.com:80	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Sites
Site Host and Port: www.app1.company.com:80 Origin Server Host and Port: app1-host1:7778 app1-host2:7778 Site Host and Port: www.app2.company.com:80 Origin Server Host and Port: app2-host:7778	Site Host and Port: www.app1.company.com:80 www.app2.company.com:80 Origin Server Host and Port: us.webche1-host:7777 us.webche2-host:7777	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Sites OracleAS Web Cache Manager: Origin Servers, Sites, and Load Balancing > Site-to-Server Mappings

Configuring an ESI Cache Hierarchy

In an ESI cache hierarchy, a provider cache stores content from an ESI provider site, and a subscriber cache stores content from the origin servers for a local site and contacts provider caches for ESI fragments. In other words, the provider cache acts as an origin server to the subscriber cache.

To configure an ESI cache hierarchy, perform the tasks in "Tasks for Setting Up OracleAS Web Cache" for each cache. When performing the tasks, take special care to perform the following:

1. Configure the correct origin server:

   • For each provider cache, configure the origin servers of the ESI provider site from the Origin Servers page of Enterprise Manager (Web Cache Home page > Administration tab > Properties > Application > Origin Servers) or OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Origin Servers).

   • For the subscriber cache, configure the origin servers of the local site and the provider caches in the Origin Servers page.

2. Create site definitions:

   • For each provider cache, create a site definition for the ESI provider site from the Sites page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Application > Sites) or the Site Definitions page of OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Site Definitions).

   • For the subscriber cache, create site definitions for the local site and each ESI provider site in the Site Definitions page.

   
   

   Note: It may not be possible to specify a site definition for all external ESI provider sites. If an ESI request is made to a provider that does not match any application Web server mapping, then OracleAS Web Cache uses DNS to resolve the site name. Note that this will not work if there is a firewall between the cache and the ESI provider. In that case, you must provide a proxy server mapping that directs the request to the appropriate proxy.

   
   

3. For both subscriber and provider caches, map the site definition to the origin server (configured in Step 0) from the Sites page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Application > Sites) or the Site-to-Server Mapping page of OracleAS Web Cache Manager (Origin Servers, Sites, and Load Balancing > Site-to-Server Mapping):

   • For the provider caches, map the site definition to the origin server of the ESI provider site.

   • For the subscriber cache, map the local site definition to the origin server for that site, and map each ESI provider site definition to its respective provider cache

4. Optionally, ensure that the ClientIP address information that is forwarded to the cache and origin server is valid.

   
   

   See Also: "Ensuring That ClientIP Headers Are Valid"

   
   

When content from the provider cache becomes invalid, an invalidation message is sent to its cache. In addition, the provider cache propagates the invalidation message to the subscriber cache.

Note: For automatic propagation of invalidation messages, OracleAS Web Cache passes the encoded invalidator password in the page request between the subscriber and provider cache during the hierarchy registration process. This HTTP traffic is susceptible to network sniffing. If the network is unprotected and insecure, configure HTTPS ports as follows: In the Ports page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Web Cache > Ports) or the Listen Ports page of OracleAS Web Cache Manager (Ports > Listen Ports) of the provider cache, disable the default HTTP port and configure an HTTPS port in its place. In the Ports page of Application Server Control Console (Web Cache Home page > Administration tab > Properties > Web Cache > Ports) or the Operations Ports page of OracleAS Web Cache Manager (Ports > Operations Ports) of the subscriber cache, disable the default HTTP port for invalidation and configure an HTTPS port in its place.

Figure 11-1 shows how to deploy support for multiple internal ESI provider sites.

Figure 11-1 Deploying Support for Multiple Internal ESI Provider Sites

Description of "Figure 11-1 Deploying Support for Multiple Internal ESI Provider Sites"

Table 11-2 shows the example settings for the deployment depicted in Figure 11-1.

Table 11-2 Settings for webche1 and webche2

Subscriber Cache webche-host	Provider Cache webche-providerhost	Setting Location in OracleAS Web Cache Manager
Port: 7777	Port: 7777	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Web Cache > Ports OracleAS Web Cache Manager: Ports > Listen Ports
Host and Port: server-host: 7778 Host and Port: provider1-host:7778 Host and Port: webche-providerhost:7777	Host and Port: provider2-host: 7778	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Origin Servers OracleAS Web Cache Manager: Origin Servers, Sites, and Load Balancing > Origin Servers
Host and Port: www.server.com:80 Host and Port: www.providersite1.com:80 Host and Port: www.providersite2.com:80	Host and Port: www.providersite2.com:80	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Sites OracleAS Web Cache Manager: Origin Servers, Sites, and Load Balancing > Site Definitions
Site Host and Port: www.server.com:80 Origin Server Host and Port: server-host:7778 Site Host and Port: www.providersite1.com:80 Origin Server Host and Port: provider1-host:7778 Site Host and Port: www.providersite2.com:80 Origin Server Host and Port: webche-providerhost:7777	Site Host Name and Port: www.providersite2.com:80 Origin Server Host and Port: provider2-host:7778	Application Server Control Console: Web Cache Home page > Administration tab > Properties > Application > Sites OracleAS Web Cache Manager: Origin Servers, Sites, and Load Balancing > Site-to-Server Mappings

Additional Hierarchy Configuration for a Cache Cluster

In a cache hierarchy, each cache cluster member acts as an independent cache. Invalidation messages are propagated from each central or provider cache cluster member to the respective remote or subscriber caches. This configuration can result in the same invalidation message being propagated multiple times by cache cluster members.

If your deployment uses a load balancer to distribute requests among cache cluster members, you can optionally configure the cache cluster members to act as one cache and to receive only one set of propagated invalidation messages.

To configure cache cluster members to act as one cache for the purposes of hierarchical caching:

1. Select a cache cluster member to represent the cache.

2. For each of the other cache cluster members, use a text editor to open the webcache.xml file.

3. Locate the CLUSTERINFO element.

4. Add the following subelements:

   <CLUSTERINFO NAME="CLUSTER_IP" VALUE="IP_address" />
   <CLUSTERINFO NAME="CLUSTER_NORM_PORT" VALUE="web_cache_listening_Port" />
   <CLUSTERINFO NAME="CLUSTER_INV_PORT" VALUE="web_cache_invalidation_port" />
   <CLUSTERINFO NAME="CLUSTER_INV_SSL" VALUE="SSL_version" />
   
   

   Table 11-3 describes how to enter values for the subelements.

   Table 11-3 CLUSTERINFO Subelements

   Subelement	Description
   CLUSTER_IP	Enter the IP address of the cache.
   CLUSTER_NORM_PORT	Enter the listening port of the cache. See Also: "Task 6: Configure OracleAS Web Cache with Listening Ports for Client Requests"
   CLUSTER_INV_PORT	Enter the invalidation port of the cache. See Also: "Task 8: Configure OracleAS Web Cache with Operations Ports"
   CLUSTER_INV_SSL	If the invalidation port is configured for HTTPS, configure the correct SSL version: NONE for HTTP-only requests (default) SSL for HTTPS requests supporting SSL version 1.0 SSLV2 for HTTPS requests supporting SSL version 2.0 SSLV3 for HTTPS requests supporting SSL version 3.0 SSLV3_V2H for HTTPS requests supporting either SSL version 2.0 or 3.0

   
   

   For example, if a cache cluster has members webche1-host, webche2-host, and webche3-host, you cans configure webche2-host, and webche3-host with settings for webche1-host as follows:

   <CLUSTERINFO NAME="CLUSTER_IP" VALUE="130.35.45.41" />
   <CLUSTERINFO NAME="CLUSTER_NORM_PORT" VALUE="9400" />
   <CLUSTERINFO NAME="CLUSTER_INV_PORT" VALUE="9401" />
   <CLUSTERINFO NAME="CLUSTER_INV_SSL" VALUE="NONE" />
   
   

   This configuration enables the cache cluster to acts as one logic cache and only webche1-host to receive the propagated invalidation messages.

5. Save webcache.xml.

6. Restart OracleAS Web Cache with the following command:

   opmnctl restartproc ias-component=WebCache