The Caching functionality is provided by the Caching feature, which is currently bundled in the Service Management feature in the WSO2 feature repository. The caching feature provides a tool that is used to cache responses for requests that are identical, thereby enhancing the response time for subsequent requests. When caching is enabled, subsequent requests with the same hash value as the previous request whose response was cached, will be served with the same cached response.
Caching can be enabled at three levels as follows. In all 3 levels, specific caching configuration steps are the same from step 4 onwards in the service-level caching configuration section described below.
- Global-Level - Global level engagement of caching will apply caching for all the messages coming into a hosted server instance. All the responses from all the services will be cached. For information on how to access global-level caching, refer to section Axis2 Modules -> Configuring the 'wso2caching' Module.
- Service-Level - If caching is engaged at service level, all the responses that are generated by all the operations of that particular service will be cached.
- Operation-Level - If engaged at operation level, only those responses from that particular operation of a given service will be cached. For information on how to access operation-level caching configuration windows, refer to section Operation Management.
Service-Level Response Caching
Follow the instructions below to add response caching to the service.
1. Log on to the product's management console and select "List" under "Services."
2. The "Deployed Services" page appears. Click on the service, for which you want to activate caching. For example,
3. The "Service Dashboard" page appears. Click "Response Caching" in the "Quality of Service Configuration" panel.
4. The "Caching Configuration for Service" page appears. In the "Enable Caching" list, click "Yes."
5. The last saved configuration or the default configuration (if it is the first time) for caching will be displayed.
Fields in Wizard:
- Hash Generator - Specifies the fully qualified class name of the hash value generator. This class implements the org.wso2.caching.digest.DigestGenerator interface. It is responsible for generating a "Hash" value for each request message, so that a matching response message can be located from the cache. The default is org.wso2.caching.digest.DOMHASHGenerator. You can implement your own "Hash" generator class and use it with the WSO2 product. However, the default hash generator should be good enough for general use.
- Timeout - Shows the time period, in milliseconds, that a cached response is kept in memory. The counting starts from the time the first request is received. Any request, received after the counter has started and is within the Timeout period, is served with the response cached upon receiving the first request. Once the Timeout expires, the cache will be updated with the response generated for the first request that was received after the expiry.
- Maximum Cache Size - Holds the maximum number of response messages that will be cached. If the maximum number of responses are already cached and none of the cached responses' Timeouts have expired, then future responses are not cached until this memory is free enough to accommodate caching a new response.
- Maximum Message Size - Shows the response message that is cached. Response messages larger than this (in size) are not cached. Caching is an expensive operation for larger messages, especially given the amount of memory required. Therefore this value should be set considering the performance and resource trade-offs.
It is advised that you consider the dynamic nature of your services before enabling caching globally. For example, an operation that is supposed to generate random numbers would not benefit from caching previous responses, because it is supposed to generate a unique response for each invocation.
6. Click "Finish." Caching will be engaged for that particular service.
Functions of Buttons:
- Finish - Click "Finish" to submit the current data. When finished, your throttle configuration will be applied and the page will be redirected to the previous page.
- Reset - Click "Reset" to load the last submitted configuration.
- Default - Click "Default" to load the default throttle configuration. If you want to submit those data, you have to click "Finish."
- Clear - Click "Clear" to clear all the text boxes in the user interface.
- Cancel - Click "Cancel" to go to the "Service Dashboard" page.