InvalidOperationException during indexing due to rule-based device resolution

[gtryf]

Issue Description

If you enable rule-based device resolution on any of the devices, you'll notice millions of errors like this one in your log files:

Exception: System.InvalidOperationException
Message: deviceRuleContext.HttpContext is null
Source: Sitecore.CES.DeviceDetection.Rules
at Sitecore.CES.DeviceDetection.Rules.RuleDeviceInformationManager.GetUserAgentFromDeviceRuleContext(DeviceRuleContext deviceRuleContext)
at Sitecore.CES.DeviceDetection.Rules.RuleDeviceInformationManager.ResolveObject[T](RuleContext ruleContext, String key, Func`2 objectFactory, String trackerDisabledMessageFormat, String deviceDetectionExceptionMessageFormat, Object[] formatArgs)
at Sitecore.CES.DeviceDetection.Rules.RuleDeviceInformationManager.GetExtendedProperty(RuleContext ruleContext, String propertyName)
at Sitecore.CES.DeviceDetection.Rules.Conditions.DevicePropertyCondition1.Execute(T ruleContext) at Sitecore.Rules.Conditions.``WhenCondition1``.Evaluate(T ruleContext, RuleStack stack)
at Sitecore.Data.Items.DeviceItem.MatchesRules(HttpContextBase httpContext, SafeDictionary`2 customData)
at Sitecore.Data.Items.DeviceItem.ResolveHelper.FindBestMatch(Database database, HttpContextBase httpContext)

You'll have to enable first-chance exception trapping to see why this happens. The issue stems from this piece of code inside /Foundation/LocalDataSource/Infrastructure/Indexing/LocalDataSourceContentField.cs:

private bool ShouldIndexItem(Item item)
{
    return item.HasLayout() && !item.Paths.LongID.Contains(ItemIDs.TemplateRoot.ToString());
}

where the HasLayout() extension method (/Foundation/SitecoreExtensions/Extensions/ItemExtensions.cs) looks like this:

public static bool HasLayout(this Item item)
{
    return item?.Visualization?.Layout != null;
}

Using a decompiler you'll find that the Layout property at some point calls into this:

ResolveDevice(database, (HttpContext.Current != null) ? new HttpContextWrapper(HttpContext.Current) : null);

and during indexing, HttpContext is null, causing the exception once for each item being indexed.

Suggested Workaround

Add a second argument to the HasLayout() extension method, namely bool resolveDevice, as follows:

        public static bool HasLayout(this Item item, bool resolveDevice = true)
        {
            if (resolveDevice)
            {
                return item?.Visualization?.Layout != null;
            } else 
            {
                DeviceItem defaultDevice = ... // Use the API to retrieve the instance's default device
                return item?.Visualization?.GetLayout(defaultDevice) != null;
            }
        }

and change the ShouldIndexItem() method inside the computed field like so:

    private bool ShouldIndexItem(Item item)
    {
      return item.HasLayout(false) && !item.Paths.LongID.Contains(ItemIDs.TemplateRoot.ToString());
    }

Please let me know if this sounds like something I should create a pull request for.

Thanks,
George

[nickwesselman]

Hi @gtryf, thanks for the report. Which version of Sitecore was this? I'm unable to repro currently on the v9 branch. This actually looks like a bug in Device Detection to me -- it should gracefully handle the lack of HTTP context in the condition, and return false. If you still think a workaround is needed, I think a better approach would be to check the layout fields directly, and just determine whether there is any Shared or Final layout on the item (or inherited from standard values).

[gtryf]

Hi @nickwesselman, I have witnessed this on versions 8.0 and 8.2 (both Initial and Update-2). Have you enabled rule based detection on at least one of your devices? You won't reproduce it otherwise.

Agreed that this is a bug in the Device Detection subsystem, however since I don't see this changing any time soon, it looks like a workaround should be implemented. The reason I suggested the approach I did is that if you statically check the shared/final layout item fields, you'll miss out on rule-based device selection when run from within a valid HttpContext (e.g. from within a rendering).

Regards,
George

[nickwesselman]

Hi @gtryf -- I'm unable to replicate on 8.2 rev 170614 with a device rule. Can you provide more specific repro steps / the specific rules you are using?