Solved Sitecore PDF Loading Issue

Are getting problem in viewing PDF files in your newly upgraded Sitecore environment? We came across the same bug while upgrading Sitecore to version 7.2 that in some browsers while opening PDF files, they get stuck. Surprisingly after that, pressing Ctrl+F5 was allowing to view PDF file. See below screenshot when the downloading stuck:

Workaround from Sitecore

In Sitecore 7.2, they gave workaround to solve the issue by forcing download of PDFs by doing below setting:

        <mediaType name="PDF file" extensions="pdf">
          <mimeType>application/pdf</mimeType>
          <forceDownload>true</forceDownload>
        </mediaType>

But, this is not the solution for our problem. We can't say our clients to download and view the PDF, it should be viewed in browser itself. We applied many tricks, and finally we solved it.

So, what was the issue?

After reverse engineering MediaRequestHandler, we came to know that Sitecore is downloading PDF content partially in range using HTTP 206 Status Code, which might be creating problems in different browser. In Sitecore versions earlier than before 6.5, Sitecore was downloading PDF or any other media in one go, which never failed.

So, one thing was sure that this bug was just because of Range Retrieval mechanism provided by Sitecore or the plug-in our browser does not support it. See below screenshot which shows how Sitecore downloads PDF content in range.

 

Final Solution

We just tried disabling the Range Retrieval Mechanism as below and found the bug resolved.

    <setting name="Media.EnableRangeRetrievalRequest" value="false" />

Many thanks to our colleague Sandeep Gupta who helped in the investigation.

Enjoy accurate media download now!!

Other Sitecore 7.2 Bugs Solved!

• Nasty Bug Found in Sitecore 7.2 Publish Related Items
• Sitecore Media Attach Detach Getting Slower

Sitecore Bug - Media Attach Detach Getting Slower

While upgrading to Sitecore 7.2, we faced another big bug regarding slowness. When we attach or detach media file or edit image file online, we found heavy load and slowness on DB server which subsides subsequently, but the browser becomes unresponsive during this time. And slowness is observed across CM platform. (We have not checked but this issue is found from Sitecore 6.5 onwards)

We have New Relic configured on CM server, which shows slow transactions. The stacktrace in all cases has same portion mentioned below:

Sitecore.Data.DataProviders.Sql.SqlDataApi.CreateReader(:0)
Sitecore.Data.DataProviders.Sql.SqlDataProvider.Exists(:0)
Sitecore.Data.DataProviders.Sql.SqlDataProvider.CheckIfBlobShouldBeDeleted(:0)
Sitecore.Data.DataProviders.Sql.SqlDataProvider.RemoveOldBlobs(:0)
Sitecore.Data.DataProviders.Sql.SqlDataProvider.SaveItem(:0)

Alongwith above stacktrace, we also found following as slowest SQL operation which is implemented in CheckIfBlobShouldBeDeleted method, which tells whether blob is used or not:

SELECT tmp.[Id] FROM 
   (SELECT sf.[Id] FROM [SharedFields] sf 
      WHERE sf.[Value] LIKE @blobId 
    UNION 
    SELECT uf.[Id] FROM [UnversionedFields] uf 
      WHERE uf.[Value] LIKE @blobId 
    UNION 
    SELECT vf.[Id] FROM [VersionedFields] vf 
      WHERE vf.[Value] LIKE @blobId 
    UNION 
    SELECT af.[FieldId] [Id] FROM [ArchivedFields] af 
      WHERE af.[Value] LIKE @blobId 
    ) tmp

Credit goes to Muktesh Mehta for drilling down the issue and Sergey Kravchenko from Sitecore Support who gave us solution for it.

We raised this to Sitecore with all above information, Sitecore provided a new config file and assembly for overriding SqlServerDataProvider, which solved our issue. You can get the assembly and config from Sitecore Support using Ticket# 412563.

Hope, this will help you if you are facing the same issue!

Media Performance Related Posts:
- IRequiresSessionState slowing down Sitecore Media Requests
- Improve Sitecore Media Performance using Reverse Proxy
- Upload Sitecore media items in selected languages

Other Sitecore 7.2 Bugs Solved!

• Nasty Bug Found in Sitecore 7.2 Publish Related Items
• Solved Sitecore PDF Loading Issue

Bug Fix in Sitecore 7.2 Publish Related Items

While testing our newly upgraded Sitecore 7.2 solution, we faced a nasty bug in newly released feature of Publish Related Items

When we ticked Publish Related Items checkbox to publish all references, it publishes all the reference items three times. You are not believing, right? Even we too when our QA raised this to us. Such a nasty bug this is!!

If you have enabled traceToLog like below for UpdateStatistics processor,

    <processor type="Sitecore.Publishing.Pipelines.PublishItem.UpdateStatistics, Sitecore.Kernel" runIfAborted="true">
        <traceToLog>true</traceToLog>
    </processor>

you will find below logs which tells the story of the bug that item named Images gets published three times.

17268 16:13:23 INFO  ##Publish Item: Name=Images, Uri=sitecore://master/{15451229-7534-44EF-815D-D93D6170BFCB}?lang=en&ver=1, Operation=Updated, ChildAction=Allow, Explanation=Version 'en_1' was published.
17268 16:13:23 INFO  ##Publish Item: Name=Images, Uri=sitecore://master/{15451229-7534-44EF-815D-D93D6170BFCB}?lang=en&ver=1, Operation=Updated, ChildAction=Allow, Explanation=Version 'en_1' was published.
17268 16:13:23 INFO  ##Publish Item: Name=Images, Uri=sitecore://master/{15451229-7534-44EF-815D-D93D6170BFCB}?lang=en&ver=1, Operation=Updated, ChildAction=Allow, Explanation=Version 'en_1' was published.

How we solved this bug:

While investigating and spending few hours we found that Sitecore is not able to remove duplicate items which are added as reference items, which we can solve by overriding RemoveDuplicateReferrers method of ProcessQueue processor as below:

Step 1: Replace below line from web.config

    <processor type="Sitecore.Publishing.Pipelines.Publish.ProcessQueue, Sitecore.Kernel"/>

with:

    <processor type="SitecoreTactics.Publishing.Pipelines.Publish.ProcessQueue, SitecoreTactics"/>

Step 2: Override the ProcessQueue processor

We have two alternatives to solve this, one is given by Ivan Sheyenko from Sitecore Support and one solved by our colleague Muktesh Mehta.

Below is the solution provided by Sitecore Support, which still needs improvements:

public class ProcessQueue : ProcessQueue
{
    // Methods
    protected override IEnumerable<publishingcandidate> RemoveDuplicateReferrers(IEnumerable<publishingcandidate> referredItems, PublishContext context)
    {
        Assert.ArgumentNotNull(referredItems, "referredItems");
        Assert.ArgumentNotNull(context, "context");
        List<publishingcandidate> list = new List<publishingcandidate>();
        foreach (IEnumerable<publishingcandidate> enumerable in context.Queue)
        {
            foreach (PublishingCandidate candidate in enumerable)
            {
                list.Add(candidate);
            }
        }
        List<publishingcandidate> list2 = new List<publishingcandidate>();
        foreach (PublishingCandidate candidate2 in referredItems)
        {
            if (!(list.Contains(candidate2) || list2.Contains(candidate2)))
            {
                list2.Add(candidate2);
            }
        }
        return list2;
    }
}

Below is the solution done by Muktesh Mehta, which is more useful in our architecture:

public class ProcessQueue : ProcessQueue
{
    // Methods
    protected virtual System.Collections.Generic.IEnumerable<publishingcandidate> RemoveDuplicateReferrers(System.Collections.Generic.IEnumerable<publishingcandidate> referredItems, PublishContext context)
        {
            Assert.ArgumentNotNull(referredItems, "referredItems");
            Assert.ArgumentNotNull(context, "context");
            List<id> idCollection = new List<id>();
            System.Collections.Generic.List<publishingcandidate> finalReferredItems = new System.Collections.Generic.List<publishingcandidate>();
            foreach (var referred in referredItems)
            {
                if(!idCollection.Contains(referred.ItemId))
                {
                    idCollection.Add(referred.ItemId);
                    finalReferredItems.Add(referred);
                }
            }
            return finalReferredItems.AsEnumerable();
        }
}

Now, enjoy bug-free Sitecore Related Item Publishing.. Njoy!

Other Sitecore 7.2 Bugs Solved!

• Sitecore Media Attach Detach Getting Slower
• Solved Sitecore PDF Loading Issue