SXA HtmlCacheClearer - only clears cache for first matching site

Question

I have a problem where when I publish an item in an SXA site, the cache does not get cleared for that site. I have a Sitecore 9.0.2 solution and the SXA site has a two "Site Grouping" items; one for master DB and one for web DB, named "Local Machine CM" and "Local Machine CD". What I find is that when viewing the Local Machine CD (which is using web) any published changes seem to cause a cache clear for the site "Local Machine CM" (which uses master). i.e. The HtmlCacheClearer class is only clearing the cache for CM. Is there some way to configure it to clear for both? I decompiled and recreated within my solution the class Sitecore.XA.Foundation.Multisite.EventHandlers.HtmlCacheClearer, Sitecore.XA.Foundation.Multisite which confirms this behaviour. I can make a code change to this class to change the behaviour, but am wondering if there is a more official way to do this?

Answer 1

That's not the official way but still it may help if anyone is looking for a fix for that issue.

Create custom HtmlCacheClearer class that inherits from Sitecore.XA.Foundation.Multisite.EventHandlers.HtmlCacheClearer and override GetAllSitesForSharedSites method:

public class HtmlCacheClearer : Sitecore.XA.Foundation.Multisite.EventHandlers.HtmlCacheClearer
{
    protected override IEnumerable<SiteInfo> GetAllSitesForSharedSites(IEnumerable<SiteInfo> usages)
    {
        try
        {
            var list = usages.ToList();
            var allowedDatabases = DatabaseRepository.GetDatabaseNames();

            var siteInfo = list.FirstOrDefault(info => allowedDatabases.Contains(info.Database) && !info.Database.Equals("core"));
            if (siteInfo == null)
                return Array.Empty<SiteInfo>();

            var database = DatabaseRepository.GetDatabase(siteInfo.Database);
            var additionalSites = new List<SiteInfo>();

            foreach (var site in list)
            {
                var rootItem = database.GetItem(SiteInfoResolver.GetRootPath(site));
                if (rootItem != null)
                {
                    if (IsSharedSite(rootItem))
                    {
                        Item tenantItem = MultisiteContext.GetTenantItem(rootItem);
                        if (tenantItem != null)
                            additionalSites.AddRange(GetSiteInfos(tenantItem.Paths.Path, list, additionalSites));
                    }
                    else
                        additionalSites.AddRange(GetSiteInfos(rootItem.Paths.Path, list, additionalSites));
                }
            }
            return additionalSites;
        }
        catch (Exception exc)
        {
            Log.Error("Exception in HtmlCacheClearer", exc, this);
        }

        return base.GetAllSitesForSharedSites(usages);
    }

    protected virtual List<SiteInfo> GetSiteInfos(
        string path,
        IEnumerable<SiteInfo> usages,
        List<SiteInfo> additionalSites)
    {
        return SiteInfoResolver.Sites
            .Where(info => info.RootPath.Equals(path) || info.RootPath.StartsWith(path + "/"))
            .Where(info => usages.All(x => !x.Name.Equals(info.Name, StringComparison.OrdinalIgnoreCase)))
            .Where(info => additionalSites.All(x => !x.Name.Equals(info.Name, StringComparison.OrdinalIgnoreCase)))
            .ToList();
    }
}

Register your cache clearer instead of original one for both publish:end and publish:end:remote events:

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <events>
      <event name="publish:end">
        <handler type="Sitecore.XA.Foundation.Multisite.EventHandlers.HtmlCacheClearer, Sitecore.XA.Foundation.Multisite">
            <patch:attribute name="type">MyAssembly.Caching.HtmlCacheClearer,MyAssembly.Caching</patch:attribute>
        </handler>
      </event>
      <event name="publish:end:remote">
        <handler type="Sitecore.XA.Foundation.Multisite.EventHandlers.HtmlCacheClearer, Sitecore.XA.Foundation.Multisite">
          <patch:attribute name="type">MyAssembly.Caching.HtmlCacheClearer,MyAssembly.Caching</patch:attribute>
        </handler>
      </event>
    </events>
  </sitecore>
</configuration>