HTTP Cache Manager

Part of the Configuration Elements category. Also documented in context in the full Component Reference.

The HTTP Cache Manager is used to add caching functionality to HTTP requests within its scope to simulate browser cache feature. Each Virtual User thread has its own Cache. By default, Cache Manager will store up to 5000 items in cache per Virtual User thread, using LRU algorithm. Use property “maxSize” to modify this value. Note that the more you increase this value the more HTTP Cache Manager will consume memory, so be sure to adapt the -Xmx JVM option accordingly.

If a sample is successful (i.e. has response code 2xx) then the Last-Modified and Etag (and Expired if relevant) values are saved for the URL. Before executing the next sample, the sampler checks to see if there is an entry in the cache, and if so, the If-Last-Modified and If-None-Match conditional headers are set for the request.

Additionally, if the “Use Cache-Control/Expires header” option is selected, then the Cache-Control/Expires value is checked against the current time. If the request is a GET request, and the timestamp is in the future, then the sampler returns immediately, without requesting the URL from the remote server. This is intended to emulate browser behaviour. Note that if Cache-Control header is “no-cache”, the response will be stored in cache as pre-expired, so will generate a conditional GET request. If Cache-Control has any other value, the “max-age” expiry option is processed to compute entry lifetime, if missing then expire header will be used, if also missing entry will be cached as specified in RFC 2616 section 13.2.4 using Last-Modified time and response Date.

Note

If the requested document has not changed since it was cached, then the response body will be empty. Likewise if the Expires date is in the future. This may cause problems for Assertions.

Name	Required	Description
Name	No	Descriptive name for this element that is shown in the tree.
Clear cache each iteration	Yes	If selected, then the cache is cleared at the start of the thread.
Use Cache Control/Expires header when processing GET requests	Yes	See description above.
Max Number of elements in cache	Yes	See description above.

Related

• CSV Data Set & Parameterization
• Thread Calculator
• Full Component Reference
• Functions and Variables