Performance Tips for the WCF SQL Adapter for BizTalk Server

I’ve recently experienced (and largely solved) some serious performance issues with the BizTalk WCF Adapter for SQL Server (aka WCF-SQL).  This post describes the problem and the solution that I discovered.

The BizTalk application in question has a fairly simple data flow:

  1. Receive a file containing multiple data records (i.e. an interchange) in XML format
  2. Use the standard XML Disassembler pipeline component to split the interchange into multiple messages
  3. Assign a static ESB Toolkit 2.0 itinerary to each message (still in the pipeline)
  4. Execute the itinerary as follows:
  5.   Map to canonical format (itinerary step 1 – messaging)
  6.   Execute a custom orchestration “service” to send the message to a SQL Server stored procedure (itinerary step 2 – orchestration)
  7.   Route the message to an off-ramp

In this application I was doing things “the ESB Toolkit way” so everything was fairly dynamic.  The maps were identified and executed on the fly and the stored procedure was called through a dynamic one-way port configured on the fly by an ESB resolver.  If you’re not using the ESB Toolkit, keep reading – these tips still apply to you.

There’s really not much to the application.  A batch of records comes in, gets split up into individual messages, and each message gets sent to a stored procedure in SQL Server using the WCF SQL adapter.  Except the performance was terrible.  On my (not-so-quick) machine, a batch containing 100 records was taking over one minute to process!

I ruled out stored procedure performance as a factor by simply changing it to immediately return without doing any work.  Surprisingly, that barely increased the speed (a few seconds at most) even though the stored procedure call now returned instantly.

I discovered a couple of things with SQL Profiler that led to the solution.

First, we were sending an XML message to the stored procedure, so the parameter was typed as ‘xml’ (the SQL Server XML data type).  However, BizTalk can’t send messages to SQL Server in that format.  It always sends them as a Unicode string.  SQL Server (or the .NET SQL client that underlies the adapter) was automatically inserting a CONVERT() on each call to turn the Unicode string into a variable of type ‘xml’, then executing the stored procedure.  To avoid this “magic” conversion, we converted the stored proc parameter to NVARCHAR(MAX) and added a CONVERT() inside the stored proc.  That moved the CONVERT() into the stored proc where SQL Server could pre-compile, optimize and cache it along with the rest of the code.

Always type your stored procedure parameter(s) as NVARCHAR(MAX) when sending an XML message to SQL Server.

Second, the major performance loss was related to the fact that this adapter is based on WCF and the fact that we were using a dynamic send port.  I realized that for every call to the stored procedure, there was also a second dynamic SQL call to obtain metadata about the stored proc’s parameters.  This was effectively doubling the number of calls to SQL Server, and running a relatively slow query to boot.

For those of you who have worked with WCF, hopefully you know that creating WCF proxy clients is a relatively expensive operation.  It is always best to cache proxy objects or at least a ChannelFactory, or take advantage of the built-in caching added in .NET 3.0 SP1.  Details on all of that are here.  The important thing is that if BizTalk is not able to cache the WCF proxy objects that it uses to talk to the WCF SQL adapter, then performance is definitely going to be bad.

That’s where the dynamic port comes in.  Since the port is dynamically configured on every call to SQL Server, the proxy objects are not cached.  This explained a lot!  On every call we were taking a hit from creating and setting up a WCF proxy object, then taking a second hit because the WCF adapter has to obtain metadata about the stored procedure before it calls it.

Avoid dynamic ports with the WCF adapters, and in particular the WCF SQL adapter, in favor of static ports with a dynamic Action.

The solution in my case was to create a static WCF-Custom port configured for the SQL adapter, leaving the Action setting blank (because we call multiple stored procedures).  Instead of fully configuring the port on the fly, I now dynamically configure only the Action property.  This produced a 45-50% increase in performance.

The end result of these changes was that processing 100 messages went from over 65 seconds to about 20 seconds.

The final tip is only relevant when you are using a fully dynamic send port with any of the WCF adapters on BizTalk 2009 and is described in this post.  Here’s another post on how to do it with the ESB Toolkit.  Performance can be modestly improved by explicitly setting the EnableTransaction and IsolationLevel context properties.  In my fully dynamic scenario, this improved performance by about 25%.  I am not clear how these settings interact with the SQL binding’s own useAmbientTransaction property.

When using dynamic ports with the BizTalk 2009 (only) WCF adapters, set the EnableTransaction and IsolationLevel context properties.

Our application is now performing at the speed that we expected, and hopefully these tips will give your own apps a nice speed boost too.