Performance of Web applications is affected by many factors. Database access, file system operations, network bandwidth are all potential affecting factors. PRADO tries in every effort to reduce the performance impact caused by the framework.
PRADO provides a generic caching technique used by in several core parts of the framework. For example, when caching is enabled, TTemplateManager will save parsed templates in cache and reuse them in the following requests, which saves time for parsing templates. The TThemeManager adopts the similar strategy to deal with theme parsing.
Enabling caching is very easy. Simply add the cache module in the application configuration, and PRADO takes care of the rest.
<module id="cache" class="System.Caching.TDbCache" />
Developers can also take advantage of the caching technique in their applications. The Cache property of TApplication returns the plugged-in cache module when it is available. To save and retrieve a data item in cache, use the following commands,
// saves data item in cache
// retrieves data item from cache
where $keyName should be a string that uniquely identifies the data item stored in cache.
Since v3.1.0, a new control called TOutputCache has been introduced. This control allows users to selectively cache parts of a page's output. When used appropriately, this technique can significant improve pages' performance because the underlying controls are not created at all if the cached versions are hit.
Changing Application Mode
Application mode also affects application performance. A PRADO application can be in one of the following modes: Off, Debug, Normal and Performance. The Debug mode should mainly be used during application development, while Normal mode is usually used in early stage after an application is deployed to ensure everything works correctly. After the application is proved to work stably for some period, the mode can be switched to Performance to further improve the performance.
The difference between Debug, Normal and Performance modes is that under Debug mode, application logs will contain debug information, and under Performance mode, timestamp checking is not performed for cached templates and published assets. Therefore, under Performance mode, application may not run properly if templates or assets are modified. Since Performance mode is mainly used when an application is stable, change of templates or assets are not likely.
To switch application mode, configure it in application configuration:
<application Mode="Performance" >
Reducing Page Size
By default, PRADO stores page state in hidden fields of the HTML output. The page state could be very large in size if complex controls, such as TDataGrid, is used. To reduce the size of the network transmitted page size, two strategies can be used.
First, you may disable viewstate by setting EnableViewState to false for the page or some controls on the page if they do not need user interactions. Viewstate is mainly used to keep track of page state when a user interacts with that page/control.
Second, you may use a different page state storage. For example, page state may be stored in session, which essentially stores page state on the server side and thus saves the network transmission time. The StatePersisterClass property of the page determines which state persistence class to use. By default, it uses System.Web.UI.TPageStatePersister to store persistent state in hidden fields. You may modify this property to a persister class of your own, as long as the new persister class implements the IPageStatePersister interface. You may configure this property in several places, such as application configuration or page configuration using <pages> or <page> tags,
<pages StatePersisterClass="MyPersister1" ... >
<page ID="SpecialPage" StatePersisterClass="MyPersister2" ... />
Note, in the above the SpecialPage will use MyPersister2 as its persister class, while the rest pages will use MyPersister1. Therefore, you can have different state persister strategies for different pages.
Server caching techniques are proven to be very effective in improving the performance of PRADO applications. For example, we have observed that by using Zend Optimizer, the RPS (request per second) of a PRADO application can be increased by more than ten times. Of course, this is at the cost of stale output, while PRADO's caching techniques always ensure the correctness of the output.