To avoid sending unnecessary
requests to the server each time a client requests a static content
item, you can configure Apache HTTP Server to set cache time-out values
for static content.
Typically, after a browser
initially downloads a static resource from the HTTP server, the browser
sends a conditional HTTP GET request each time the browser encounters
that resource again. For example, when a browser first downloads a
SAS Web Report Studio logo image, the browser stores a local copy
of the image. For each subsequent page that references the logo, the
browser requests that the image be sent again if the image has been
modified since the previous download. This sequence occurs for every
static element and can result in large numbers of HTTP requests. Because
the static content for is not modified often, most of these requests
are unnecessary.
When you specify a cache
time-out for each static element, clients (browser, proxy, or server
cache) can avoid sending unnecessary requests to the HTTP server in
order to check the validity of the content. When the browser first
accesses a static element, the browser stores that element locally
for the duration of the time-out value that is configured. During
this time, subsequent queries to the HTTP server are suppressed for
that element. The browser resumes queries as appropriate when the
time-out period elapses within the session.
You can configure Apache
HTTP Server to set cache time-out values for static content. This
is true whether Apache HTTP Server is configured to serve that static
content or is merely a reverse proxy to your Web application server.