You can disable browser caching by changing this setting in Sitecore to true:
<setting name="DisableBrowserCaching" value="true" />
BUT that really is not a good move to make, disabling the browser caching on clients will cause a higher load on your servers when most of the time, you don't need to do that.
What you need to do is work out your caching strategy and how long you want things like images to live in the clients browser cache. I normally use a sliding scale based on the age of the content/media item.
One thing to keep in mind, once the browser cache has been set, there is nothing you can do about it from the server!! The user will have to manually clear the browser cache to force an update.
A simple option would be to use the current context item to set the cache headers. Adding this processor to the renderLayout pipeline will do that:
public class BrowserCaching : RenderLayoutProcessor
{
/// <summary>
/// Set browser caching headers.
///
/// </summary>
/// <param name="args">The arguments.</param>
public override void Process(RenderLayoutArgs args)
{
Assert.ArgumentNotNull(args, "args");
Profiler.StartOperation("Update browser caching headers.");
var page = Context.Page;
if (page?.Page == null)
{
return;
}
SetCacheHeaders(page.Page);
if (Context.Item != null)
{
SetUpdateHeaders(Context.Item, page.Page);
}
Profiler.EndOperation();
}
/// <summary>
/// Set caching related headers
///
/// </summary>
/// <param name="page">The page.</param>
private static void SetCacheHeaders(Page page)
{
if (Context.Site == null && !Settings.DisableBrowserCaching || Context.Site != null && !Context.Site.DisableBrowserCaching)
{
// TODO: Build a sliding scale here based on the age of the Context.Item
page.Response.Cache.SetMaxAge(new TimeSpan(0, 0, 30));
return;
}
Tracer.Info("Adding Http headers to disable caching.");
page.Response.Cache.SetNoStore();
page.Response.Cache.SetCacheability(HttpCacheability.NoCache);
}
/// <summary>
/// Set time-of-last-update headers
///
/// </summary>
/// <param name="item">The item.</param><param name="page">The page.</param>
private static void SetUpdateHeaders(Item item, Page page)
{
var date = item.Statistics.Updated;
if (date > DateTime.Now)
{
date = DateTime.Now;
}
Tracer.Info("Adding Http header to indicate last modification.", "Date: " + date + ".");
page.Response.Cache.SetLastModified(date);
}
}
This code sets the max-age of the response and also sets the last modified date. Browsers should be able to use that to know when to expire the cached copy of the data. As for the sliding scale, you will need to work out what is best for your implementation. As a baseline, I keep young items, so 2-3 hours old or less at around 60 seconds max-age, and then grow that. If a media item is more than a week old, I'm setting the max age in days rather than seconds.
Obviously this example only does the current context item, so pages that have lots of Datasources may need to calculate it from the datasource and for media items you will need to add this to the media request pipelines.
