Oracle Web Cache Request Flow

Configuring High Availability for Web Tier Components 9-15 process handles client requests serving content back to the client. The admin server process provides administration, configuration, and monitoring capabilities.

9.3.1.2 Oracle Web Cache Process Monitoring

You manage the cache and admin server processes withOracle Process Manager and Notification Server OPMN using the Fusion Middleware Control, Oracle Web Cache Manager, or the opmnctl utility, as described in the Oracle Fusion Middleware Administrators Guide for Oracle Web Cache.

9.3.1.3 Oracle Web Cache Startup and Shutdown Lifecycle

OPMN is responsible for the direct start, stop, restart, and monitoring of the cache server and admin server processes. Anytime the Oracle Web Cache configuration is statically modified, you must stop and restart Oracle Web Cache processes: The executable for the cache process is webcached, and the executable for the admin server process is webcachea. These executables reside in the following directories: UNIX ORACLE_HOMEwebachebin Windows ORACLE_HOME\bin When you stop Oracle Web Cache, all objects are cleared from the cache. In addition, all statistics are cleared. After you configure Oracle Web Cache, restart Oracle Web Cache. In addition, if you change the administrator password, restart the admin server. To restart Oracle Web Cache, use one of the following tools: ■ Use Fusion Middleware Control or the opmnctl command-line utility to restart the cache or admin server processes. ■ Use Oracle Web Cache Manager to restart the cache server process. You must restart both the cache server and admin server processes if you modified one of the following configuration settings: ■ Administration port properties ■ Trusted subnets ■ User and group ID information See the Oracle Fusion Middleware Administrators Guide for Oracle Web Cache for further information about starting and stopping Oracle Web Cache.

9.3.1.4 Oracle Web Cache Request Flow

Figure 9–4 shows further details of the request flow within the Oracle Web Cache tier. 9-16 Oracle Fusion Middleware High Availability Guide Figure 9–4 Request Flow to Oracle Web Cache within the Web Tier As shown in Figure 9–4 , the following occurs within the Oracle Web Cache tier: 1. The incoming browser request is analyzed for the correct HTTP format. 2. The browser request is then further analyzed to determine if it is in HTTPS format: a. If the browser request is in HTTPS format, Oracle Web Cache decrypts SSL. b. If the browser request is not in HTTPS format, Oracle Web Cache parses the request. 3. After the request is understood, it is filtered by a set of prescribed filtering rules. 4. A cache lookup is performed to see if the HTTP request was sent previously and is present in the cache. If the request is present in the cache, a cache hit, the request is compressed and the content is sent directly to the browser. If the request is not present in the cache, a cache miss, then either: a. The request is sent directly to a single origin server. b. The request is sent to load-balanced origin servers. Was request HTTPS? Yes Parse Request Apply Request Filtering Rules Incoming Browser Request No Cache Lookup In Cache? No Cache Miss Yes Cache Hit Multiple Origin Servers? Yes No Load Balance to Pick Origin Server Send Request to Origin Server Is Object Cacheable? No Yes Insert Cacheable Object in Web Cache Compress and Serve Object Response Perform SSL Decryption Configuring High Availability for Web Tier Components 9-17 Each load balanced origin server pings each Oracle Web Cache server on a periodic basis to check the status of the cache. The load balancer distributes any incoming requests among cache cluster members. If Oracle Web Cache does not have the requested content or the content is stale or invalid, it hands the request off to the application Web server. The application Web server sends the content to Oracle Web Cache. Oracle Web Cache sends the content to the client and stores a copy of the page in cache. The proxy server is placed in a less secure zone, the Demilitarized Zone DMZ, instead of the origin server. Caching rules determine which objects are cached. When you establish a caching rule for a particular URL, those objects contained within the URL are not cached until there is a client request for them. When a client first requests an object, Oracle Web Cache sends the request to the origin server. This request is a cache miss. Because this URL has an associated caching rule, Oracle Web Cache caches the object for subsequent requests. When Oracle Web Cache receives a second request for the same object, Oracle Web Cache serves the object from its cache to the client. This request is a cache hit. When you stop Oracle Web Cache, the cache clears all objects. In addition, Oracle Web Cache clears and resets statistics.

9.3.1.5 Oracle Web Cache Configuration Artifacts