The WSO2 Application Server (AS) provides a caching 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 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.
Adding response caching reduces the overhead of XML processing or object copying. It helps clients to participate transparently in the existing Web services community.
The caching option is disabled by default, therefore it must be enabled.Figure 1: Configuration for Response Caching
Field Name | Description |
Hash Generator | This 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 Application Server. However, the default hash generator should be good enough for general use. |
Timeout | This is 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 | This 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 | 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. |
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