Sitecore’s SessionDictionaryData class saves the day

More and more projects are using Azure SQL as the database back-end for Sitecore (so long as they’re running Sitecore 8.2 and newer — if alignment to Sitecore official support guidance is important to you). This sets up a new class of performance considerations around Azure SQL, and I want to share one tuning option we learned while investigating high DTU usage for the Sitecore xDB “ReferenceData” database in a Sitecore 9 PaaS build. We wanted to off-load some of the work this “ReferenceData” database was doing, and investigations into which Azure SQL queries were causing the DTU spikes pointed to INNER JOINs between the ReferenceData.DefinitionMonikers and ReferenceData.Definitions tables.

Sitecore support pointed us in the right direction at this juncture, since the default DictionaryData was using AzureSQL for persistence — we should consider a store more suited to rapid key/value access. If this sounds like a job for Redis, you’d be correct, and fortunately Sitecore has an implementation that’s suited for this type of dictionary access in the Sitecore.Analytics.Data.Dictionaries.DictionaryData.Session.SessionDictionaryData class.

The standard Sitecore pipeline we’re talking about is the getDictionaryDataStorage pipeline and it’s used by Sitecore Analytics to store Device, UserAgent, and other key/value pair lookups. Here’s it’s definition:

The alternative we moved to is to use session state for storing that rapidly requested data,  so we updated the DictionaryData node to instead use the class Sitecore.Analytics.Data.Dictionaries.DictionaryData.Session.SessionDictionaryData. For this Azure PaaS solution, it amounts to using Azure Redis for this work since that’s where the session state is managed. Here’s the new definition:

What this boils down to is the implementation in Sitecore.Analytics.DataAccess.dll of Sitecore.Analytics.DataAccess.Dictionaries.DataStorage.ReferenceDataClientDictionary was shown to be a performance bottleneck for this particular project, so changing to use the Sitecore.Analytics.dll with it’s Sitecore.Analytics.Data.Dictionaries.DictionaryData.Session.SessionDictionaryData aligns the project to a better-fit persistence mechanism.

We considered if we could improve upon this progress by extending the SessionDictionaryData class to be IIS in-memory regardless of the Sitecore session-state configuration; there would be no machine boundary to cross to resolve the (apparently) volatile data. Site visitors would require affinity to a specific AppService host in Azure, though, with this and it’s possible – or even likely — that Sitecore assumes this is shared state across an entire implementation. We talked ourselves out of seriously considering a pure IIS in-memory solution.

I think it’s possible we could improve the performance with the default ReferenceDataClientDictionary by tuning any caches around this analytics data, but I didn’t look into that since time was of the essence for this investigation and the SessionDictionaryData class looked like such a quick win. I may revisit that in the next iteration, however, depending on how this new solution performs over the long term.

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The case of the Inventory gotcha with Azure SQL and Sitecore Commerce 8.2.1

I only recently discovered comments to this blog were going into an unmonitored spam folder — my apologies if anybody had their hearts set on a response to their comment!  In scanning some of those comments, I thought a proper response was warranted to one note on a piece I wrote about a hard to find Sitecore Commerce configuration setting.

I started that post by writing:

After recently swapping the backing store from Azure SQL to SQL Server (due to an interesting Inventory gotcha with the Reference Storefront that I’ll maybe share at some other time), I’m finding nooks and crannies of configuration I never knew existed with the Commerce product until now.

This post discusses the interesting Inventory gotcha with the Sitecore Commerce storefront implementation. I should point out this is relevant to Sitecore Commerce 8 and I’ve not tested this specifically with Sitecore Commerce 9, but I assume it’s been addressed in version 9 by either not using the same Reference Storefront for Commerce (in version 9 you’d be steered to an SXA UI instead of the older “Reference Storefront”) or by the general platform improvements in Sitecore Commerce 9.  I guess you can stay tuned for Sitecore Commerce 9 news on this front!

The Problem Scenario

This is IaaS VMs running Sitecore 8 (conventional IIS, not PaaS) and using the Sitecore Commerce 8.2.1 release in a scaled Sitecore environment. Azure SQL was chosen as the database technology for a variety of reasons I need not go into. This implementation used separate Commerce catalogs for CM servers and CD servers, to provide the “publish workflow” behavior Sitecore uses for marketing content; this is accomplished for Commerce via the Staging Service.

One tricky area when using multiple Commerce catalogs is Inventory. A late-breaking customer requirement was the need for inventory updates to flow real-time between content management and content delivery servers, so nobody sees stale inventory data. Don’t you love those late-breaking customer requirements?

This can be handled in different ways, but the method appropriate to this project was to use a single Inventory database that both Sitecore CM and CD environments would reference for inventory data.  Commerce Server Manager presents this in the UI as the “Inventory” resource under the Commerce site:

commerceInventory

It’s smart to have separate databases for product catalog and inventory, and we set this solution up to have multiple catalogs (one for CM and one for CD) with a shared Inventory database so that data was always realtime.

The crux of the problem was the mechanism Sitecore’s Reference Storefront uses to coordinate Inventory queries between the two Commerce catalog databases — it’s called Cross Database Query and it’s not supported the same way in Azure SQL as it is in conventional SQL Server.  You can do cross database queries with Azure SQL, just not the way the Reference Storefront for Sitecore Commerce depends on it.

The exception we would see was as follows:

SqlException (0x80131904): Reference to database and/or server name in ‘CFSolutionStorefrontSite_productcatalog.dbo.Habitat_Inventory_InventorySkus’ is not supported in this version of SQL Server.

The above was followed by a fair amount of StackTrace such as:

System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) +3189408
 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) +753
 System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) +5042
 System.Data.SqlClient.SqlDataReader.TryConsumeMetaData() +87
 System.Data.SqlClient.SqlDataReader.get_MetaData() +101
 System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption) +590

You get the idea.

What We Considered

After considering our Sitecore Commerce configuration and confirming it was solid, the exception next had us examining Azure SQL compatibility settings, but that wasn’t the issue.

We determined we could do an import/export of Inventory data.  Maybe the Sitecore publish:end event could push inventory changes to the CD servers, where they store inventory in an XML file and on publish:end:remote we could import that XML data into the Content Delivery servers.

We could remove publishing from the equation and use a scheduled <agent> to move Inventory data around.

What We Actually Did

The import/export options were never going to be truly realtime, at least not sufficiently “real” for our project and their inventory requirements. So we swapped out the database back-end and used SQL Server in IaaS VMs instead. Cross database query worked as expected, and we could use a central Inventory database with multiple Commerce Catalog databases for CM and CD sites. It worked as it should.

This concludes the tale of the interesting Inventory gotcha around Sitecore Commerce 8.2.1 — this should close the loop with the initial post from a few months ago, I hope this helps out somebody else!

Sitecore Commerce 8.2.1 Firewalls & Azure SQL Notes

I know Sitecore Commerce 9 is just around the corner, but I know many projects are under way with the current Sitecore Commerce 8.2.1 and I wanted to share some notes we’ve collected on how to work with the technology.

This is from lessons our team at Rackspace has collected, including some exceptionally talented “sales weasels” who have really dug into the Commerce platform with us to determine perf benchmarcks etc — score 1 for the talented sales weasels ξ(^◒^)ξ !

These two links are the key pillars of online documentation for getting started with the product:

http://commercesdn.sitecore.net/SitecoreCommerce/DeploymentGuide/en-us/index.html

http://commercesdn.sitecore.net/SitecoreCommerce/DevOpsGuide/en-us/index.html

As a complement to the above, I’d like to share the following tips we’ve learned on a few Sitecore Commerce 8.2.1 projects . . .

Firewall Settings

We’ve run into issues with both the Sitecore Commerce Staging software and the Profile system; the exceptions are logged to the Windows Event log or the Sitecore logs and can report an ugly COM error such as the following . . .

don't panic
Don’t panic

. . . it turns out that the current documentation doesn’t mention Firewall rules for these two services to operate.  After some investigation we realized we needed to open up ports.  Prior versions of Sitecore Commerce have this article, http://commercesdn.sitecore.net/SCpbCS82/SitecoreCommerceDeploymentGuide/en-us/FirewallPorts.html, and it turns out port ranges 5000-5030 and 507 can be important to proper communications in a distributed Sitecore Comemrce build.

Azure SQL

Everyone is price conscious and Azure SQL can save customers a lot of money over conventional SQL Server.  Documentation online for 8.2 states Azure SQL is supported, but the installation documentation doesn’t treat it as a first-class citizen.  There is this great link, http://commercesdn.sitecore.net/SCpbCS81/SitecoreCommerceDeploymentGuide/en-us/c_UsingAzureSQLwithCS.html, with notes on Azure SQL specific provisioning for Sitecore Commerce — but it’s organized under a PaaS installation topic which hides it from our IaaS Sitecore Commerce eyes.

Generally speaking, the Initialize-CSSite script modifies the SQL database schemas and does not work if you use Azure SQL.  The authentication assumptions are invalid (using an App Pool user isn’t going to fly with Azure SQL).

This can be worked around (mostly), but we learned the hard way that the Sitecore Commerce Reference Storefront application is not compatible with Azure SQL in the reliance on Cross-Database queries for certain key operations; in our case, trying to use a central Commerce Inventory Azure SQL database was ultimately untenable.  Azure SQL does offer Cross-Database queries, but the syntax is different and the Reference Storefront code has non-trivial dependencies on the IaaS SQL Server understanding of querying between databases.

There are a lot of nooks and crannies with Sitecore Commerce 8.2.1.  I know everyone is excited about a fresh start with Sitecore Commerce 9 that doesn’t include the legacy COM and thick-client dependencies; this write-up summarizes a few of the Commerce highlights on the horizon.  For now, however, there are Commerce 8.2.1 builds in the wild that require our attention and I hope the above notes help others to be successful.

How a 13 year old archived list serv helped me out with Sitecore Commerce

Sitecore Commerce is an interesting landscape — it’s never a dull moment.  After recently swapping the backing store from Azure SQL to SQL Server (due to an interesting Inventory gotcha with the Reference Storefront that I’ll maybe share at some other time), I’m finding nooks and crannies of configuration I never knew existed with the Commerce product until now.

After I migrated to Azure IaaS SQL Server VMs from Azure SQL, I thought I had everything tidied up.

  • Commerce Server Manager references?  ✔
  • Sitecore application connection strings?  ✔
  • Bootstrap configuration (I posted this gist on manipulating those files to make this easier)? 

I updated the Azure SQL database credentials to prove that I had no lingering connections to Azure SQL.  I encountered an exception at Sitecore start-up related to initialization of the profile service, however, and had to start digging.  CommerceProfileSystemException was the exception type and the stacktrace started as follows:

Exception type: CommerceProfileSystemException 
 Exception message: Failed to initialize profile service handle.
 at CommerceServer.Core.Runtime.Profiles.ProfileContext..ctor(String profileServiceConnectionString, String providerConnectionString, String bdaoConnectionString, DebugContext debugContext)
 at CommerceServer.Core.Runtime.CommerceContextFactory.CreateProfileContext()
 at CommerceServer.Core.Runtime.CommerceContextFactory.get_ProfileContextSingleton()
 at CommerceServer.Core.Runtime.Profiles.CommerceProfileModule.get_ModuleProfileContext()
 at CommerceServer.Core.Runtime.Profiles.CommerceProfileModule.get_ProfileContext()

The Commerce Server Manager encapsulates the connection strings, and I thought I had them all updated to the SQL Server VM equivalents, even going so far as to inspect MSCS_Admin in SQL Server with a query like this:

SELECT [i_ResourceID]
 ,[s_PropertyName]
 ,[s_Value]
 FROM [MSCS_Admin].[dbo].[ResourceProps]
 where f_IsConnStr=1
 ORDER BY 1

While interesting to find where this information is stored (may or may not be permanent, though — tough to tell with Commerce!), this output didn’t shed light on what might be going on, though:

Eventually I stumbled across some 13 year old documentation on Commerce Server discussing updating the ProfileService data source in some detail (http://microsoft.public.commerceserver.general.narkive.com/NPLMLusv/commerce-2002sp3-on-windows-2003-can-t-change-profiles-data-source).  It turns out, this 13 year old solution was completely applicable to my 2017 Sitecore Commerce predicament.

Succinctly, within Commerce Server manager you should do the following:

  1. Expand the Commerce Server “Global Resources” node, then “Profiles” node, then “Profile Catalog” node, then “Data Sources” node, and finally expand the “ProfileService_SQLSource” node
  2. Click on the Partitions node:
  3. In the right pane, there’s a SQLSource element you right-click and choose “Properties”
  4. Select the Partitions Tab, then “Edit” the connection string
  5. Make your connection string modifications here.  This is where my elusive reference to Azure SQL was hiding and causing Sitecore to fail to initialize.

The more work I do with Sitecore Commerce, the more I’m appreciating the value of the older documentation targeting previous editions of the product.  The catch is, it’s not 100% relevant to the modern experience with Sitecore Commerce . . . and knowing what is and isn’t applicable to the Sitecore Commerce 8.2.1 world is a challenge.  I think we’re getting there, a little bit at a time!

Encrypting Sitecore connection strings for Sitecore Commerce, Azure SQL, and beyond

There’s been a lot of Sitecore Commerce on my plate this Summer, and sadly one limitation of using that product for some customers is the requirement for SQL Server authentication instead of Active Directory and Windows Auth; I won’t get into why they need SQL auth at this point, but trust that in many use-cases this is a necessity.

In an effort to always deliver a secured platform for customers, at Rackspace we encrypt the App_Config/connectionStrings.config file to avoid having plaintext usernames and passwords on disk.    This is a link to our Rackspace GitHub “gist” performing such encryption with the ASP.Net tool aspnet_regiis.exe.  The logic is also there to un-encrypt, in case that’s necessary.

Encryption success
You can update the $configLocation variable at the top of the script to point to where your Sitecore installation is located; you then run this script using PowerShell, and you’ll get an output like this.

Once you’ve run the script, your connectionStrings.config file will resemble this:

Before you get too excited, for Sitecore Commerce in the current incarnation, there are several other plaintext passwords on disk in the \CommerceAuthoring\wwwroot\data\Environments and related .json files for both SQL and Sitecore.  The PowerShell I’ve shared doesn’t address those areas.  The Sitecore Commerce documentation does a good job of cataloging where to find these references, at least, but this still leaves a lot to be desired in terms of security.

I’m not going to go too far down this path, since I mostly wanted to post the PowerShell we use to automate SQL Server connection string encryption.  This technique can be useful for a variety of projects, not just for Sitecore Commerce — although this is the use case we’re repeatedly seeing right now.  If I have time, I’ll share some other Sitecore Commerce tips around Azure SQL friendly deployments (Sitecore’s documentation is a decent start, but lacking in some respects).

Here’s the script to encrypt/decrypt those Sitecore connectionStrings.config file:

Azure Search compared to Solr for Sitecore PaaS (Chapter 2: Querying)

I carried forward my Azure PaaS benchmarking work from earlier this month (see this post on the indexing side of the equation for the start of the story).

For a quick refresher, I’ve used an ARM template based deployment of Sitecore to get a system resembling the following:

ARM Templates Arch

The element I’m exercising in the benchmarks is how Sitecore’s web servers work with the “Search” icon in the diagram above.  I tackled the document ingestion side (how data gets into the search indexes) in my earlier post.  This post addresses the querying side of things (how data gets out of the search indexes).

By default, Azure PaaS search with Sitecore is configured to use Azure Search.  Solr is another viable option.

Here’s where I’ll interject that Coveo also has an excellent search technology for Sitecore.  There are specific use-cases where Coveo is a strong fit, however, and in my indexing the sitecore_core_index evaluations in the earlier post Coveo would not be considered a good fit.  This changes, however, for the set of benchmarks I’ve run in this post.  I am in the process of testing the Coveo approach in Azure PaaS for Sitecore . . . it’s hot off the presses, so there are still rough edges to work around . . . but Coveo is not part of this write-up for the time being.  I will post an update here once I’ve completed the analysis involving Coveo.

In considering Azure Search vs Solr, I used a methodology with JMeter laid out in a great KB article from Sitecore at https://kb.sitecore.net/articles/398589.  I have a LaunchSitecore site running and I use JMeter to automate visits to the site, simulating simple user behaviour.  I don’t go too crazy with this, because I’m more interested in exercising a basic Sitecore work load than doing a deep-dive in xDB traffic simulation.

My first post showed a clear advantage to Solr for the indexing side of search, but for the querying side I can say there is very little variance between Azure Search and Solr.  Sitecore does a good job of protecting data repositories with layers of data and html caches, but even with those those features disabled (we’re talking cacheHtml=”false”on the site definition, <cacheSizes> configuration all set to a heretical zero (“0”), etc) there isn’t a significant difference between the two technologies.

I’m not going to put up a graph of it, because the throughput as measured by JMeter for tests of 20, 50, 100, 200, or  more visitors performed almost the same.

I could develop a more search heavy set of benchmarks, performing a random dictionary of searches against a large custom index that Sitecore responds to but must bypass all caches etc, but that feels like overkill for what I’m looking to achieve.  Maybe that’s appropriate once I bring Coveo into the benchmarking fun.

For this, I wanted to get a sense for the relative performance between Azure Search and Solr as it relates to Sitecore PaaS and I think I’ve done that.  Succinctly:

  1. Solr is considerably faster at search indexing (courtesy of the search provider implementation in Sitecore)
  2. both Azure Search and Solr perform about the same when it comes to querying a basic Sitecore site like LaunchSitecore (again, courtesy of the search provider implementation in Sitecore)

This isn’t the definitive take on the topic.  It’s more like the beginning.  Azure Search is native to Azure, so there are significant advantages there.  There is a lot of momentum around Azure and Sitecore in general, so that story will continue to evolve.

There are Solr as a service options out there that make Solr for Sitecore much easier (such as www.measuredsearch.com which I’ll blog about in the next few days), but Solr can be a lot for corporate IT departments to take on, so it isn’t a simple choice for everyone.

 

 

Azure Search compared to Solr for Sitecore PaaS (Chapter 1: Ingestion)

I’ve been investigating Azure PaaS architectures for Sitecore lately, and I wanted to take a few minutes and summarize some recent findings around the standard Sitecore search providers of Solr and, new for Sitecore PaaS, Azure Search.

To provision Azure PaaS Sitecore environments, I used a variant of the ARM Template approach outlined in this blog.  For simplicity, I evaluated a basic “XP-0” which is the name for the Sitecore CM/CD server combined into a single App Service.  This is considered a basic setup for development or testing, but not real production . . . that’s OK for my purposes, however, as I’m interested in comparing the Sitecore search providers to get an idea for relative performance.

The Results

I’ll save the methodology and details for lower in this post, since I’m sure most don’t want to wait for an idea for the results.  The Solr search provider performed faster, no matter the App Service or DB Tier I evaluated in Azure PaaS:

ChartComparison

The chart shows averages to perform the full re-index operation in minutes.  You may want to refer to my earlier post about the lack of HA with Sitecore’s use of Azure Search; rest assured Sitecore is addressing this in a product update soon, but for now it casts a more significant shadow over the 60+ minutes one could spend waiting for the search re-index to complete.

Methodology

In these PaaS trials, I setup the sample site LaunchSitecore.  I performed rebuilds of the sitecore_core_index through the Sitecore Control Panel as my benchmark; I like using this operation as a benchmark since it has over 80,000 documents.  It doesn’t particularly exercise the querying aspects of Sitecore search, though, so I’ll save that dimension for another time.  I’ve got time set aside for JMeter testing that will shed light on this later…

To get the duration the system took to complete the re-index, I queried the PaaS Sitecore logs as described in this Sitecore KB article.  Using results like the following, I took the timestamps since I’ve found the Sitecore UI to be unreliable in reporting duration for index rebuilds.

queries

You can get at this data yourself in App Insights with a query such as this:

traces
| where timestamp > now(-3h)
| where message contains " Crawler [sitecore_core_index]" 
| project timestamp, message
| sort by timestamp desc

Remember, I’ve used the XP0 PaaS ARM Templates which combine CM and CD roles together, so there’s no need for the “where cloud_RoleInstance == ‘CloudRoleBlahBlah'” in the App Insights query.

Methodology – Azure Search

For my Azure Search testing, I experimented with scaling options for Azure Search.  For speedier document ingestion, the guidance from Microsoft says:

“Partitions allow for scaling of document counts as well as faster data ingestion by spanning your index over multiple Azure Search Units”

The trials should perform more quickly with additional Azure Search Partitions, but I found changing this made zero difference.  My instincts tell me the fact Sitecore isn’t using Azure Search Indexers could be a reason scaling Azure Search doesn’t improve performance in my trials.  Sitecore is making REST calls to index documents with Azure Search, which is fine, but possibly not the best fit for high-volume operations.  I haven’t looked in the DLLs, but perhaps there’s other async models one could use in the the Azure Search provider when it comes to full re-indexes?  It could also be that the 80,000 documents in the sitecore_core_index is too small a number to take advantage of Azure Search’s scaling options.  This will be an area for additional research in the future.

Methodology – Solr

To host Solr for this trial, I used a basic Solr VM in the Rackspace cloud.  One benefit to working at Rackspace is easy access to these sorts of resources 🙂  I picked a 4 GB server running Solr 5.5.1.  I used a one Solr core per Sitecore index (1:1 mapping), see my write-up on Solr core organization if you’re not following why this might be relevant.

For my testing with the Solr search provider, Sitecore running  Azure PaaS needed to connect outside Azure, so I selected a location near to Azure US-East where my App Service was hosted.  I had some concerns about outbound data charges, since data leaving Azure will trigger egress bandwidth fees (see this schedule for pricing).  For the few weeks while I collected this data, the outbound data fee totaled less than $40 — and that includes other people using the same Azure account for other experiments.  I estimate around 10% (just $4) is due to my experiments.  Suffice it to say using a Solr environment outside of Azure isn’t a big expense to worry about.  Just the same, running Solr in an Azure VM would certainly be the recommendation for any real Sitecore implementation following this pattern.  For these tests, I chose the Rackspace VM since I already had it handy.

I’d be remiss to not mention the excellent work Sitecore’s Ivan Sharamok has posted to help make Solr truly enterprise ready with Sitecore.  Basic Auth for Solr with Sitecore is important for the architecture I exercised; this post is another gem of Ivan’s worth including here, even if I didn’t make use of it in this specific set of evaluations.  Full disclosure: I worked with Ivan while I was at the Sitecore mothership, so I’m biased that his contributions are valuable, but just because I’m biased doesn’t mean I’m wrong.

Conclusions

I’ll include my chart once again:

ChartComparison

These findings lead me to more questions than answers, so I’m hesitant to make any sweeping generalizations here.  I’m safe declaring Sitecore’s search provider for Solr to be faster than the Azure Search alternative when it comes to full index re-builds, that’s clear by an order of magnitude in some cases.  Know that this is not a judgement about Solr versus Azure Search;  this is about the way Sitecore makes use of these two search technologies out of the box.  The Solr provider for Sitecore is battle-tested and has gone through many years of development; I think the Azure Search provider for Sitecore could be considered a beta at this point, so it’s important to not get ahead of ourselves.

A couple other conclusions could be:

  1. Whether using Solr or Azure Search, there is no improvement to search re-index performance when changing between the S3 to P3 tiers in Azure App Services.
  2. Changing from the S1 to S3 tiers, on the other hand, makes a big perf difference in terms of search re-indexing.
    • Honestly, the S1 tier is almost unusable as the single CPU core and 1.75 GB RAM are way too low for Sitecore; the S3 with 4 cores and 7 GB RAM is much more reasonable to work with.

Next Up

It’s time for me to consider the more fully scaled PaaS options with Sitecore, and I need to exercise the query side of the Sitecore search provider instead of just the indexing side.