I lost a couple hours today to perhaps the most obscure WCF error message I have encountered yet. I do tons of WCF and have been working with WCF extensively since 2003 timeframe when I had access to the private betas. I would consider myself a top expert on WCF, and yet this one really was kicking me in the butt. Without a methodical approach to troubleshooting it, I never would have sorted it out.

Most WCF errors, after developing a good experience base with the technology, you can rapidly solve. You will either get to know some common ones and know where to jump in your configuration to sort it out, or you can Bing/Google the error message and you will usually find some forum posts where someone suggests the right configuration fix.

I was putting together a very simple WCF call from a client to a service, using username security with the WsHttpBindiing. When I got everything set up the way I had done hundreds of times before, I was getting an exception whenever I tried to make the method call on the client.

The error I got stuck on was telling me this:

Outer exception: An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail.

Inner Exception: An error occurred when verifying security for the message.

OK, fine. I’ve seen those many times before. Went back and quadruple checked all my security settings on both the client and server. All seemed well there. Time to search. Lots of people have apparently had this error, and every solution I found had to do with making sure the clock on the client and server were matched up. Hmm, I’m running client and server localhost. I’m no time-space continuum expert, but I’m relatively certain when two parties reference the same clock, they are in sync.

So then it became an exercise in eliminating variables.

Change the service method to return null to eliminate some kind of serialization error. No, not it.

Snap back to a default WsHttpBinding with no modifications. All works well there. Gotta be the binding.

So I look closer at what I had hacked together for a server binding:

<wsHttpBinding>
  <binding name="MyBinding" maxReceivedMessageSize="20000000">
    <security mode="Message">
      <message clientCredentialType="UserName"/>
    </security>
    <!--Remove the readerQuota or increase its size, problem goes away-->
    <readerQuotas maxArrayLength="2000"/>
  </binding>
</wsHttpBinding>

Thanks to the fact that I had just observed a conversation on a connected systems email alias regarding maxBufferSize and why it doesn’t exist on WsHttpBinding, it occurred to me that it could be my (arbitrarily chosen) message size or array length.

Sure enough, if I removed the readerQuotas maxArrayLength altogether, or just bump it up by one extra zero, the problem disappeared. I know that there is some coupling between maxReceivedMessageSize and maxArrayLength, but don’t know the specific rules off the top of my head. But I just wanted to get this out there that if you have those errors indicating security problems and you are convinced your security is configured correctly, try tinkering with your sizes in the binding. That could very well be the cause as it was for me.

You can download a sample application that demonstrates the problem here.

Thursday, July 23, 2009 3:44:56 PM (GMT Daylight Time, UTC+01:00)
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If you are building a highly extensible application, the right answer these days seems to be to look into MEF. It is a very flexible approach to extensibility and plug ins that works for 3.5 and will become part of the .NET Framework in 4.0.

However, sometimes you just need a simple plug in capability to load some components provided by others. If there is any chance those plug ins will depend on each other and need to talk to each other, bite the bullet and learn and use MEF. But if they just need to be loaded up and called, you can use a simple factory to get the job done. About 4 years ago, I put together a little sample of doing this with a generic factory class here.

A similar requirement came up with a customer this week, but with one twist: we were already using a DI container (Unity) and the plug ins that were going to load were going to have dependencies on some objects and services that the DI container already knew about.

Since the container is really a generic factory itself, I decided to put together a little sample of using Unity as a plug-in factory and thought I would share it here.

Defining the Plug-ins

The first step to a plug-in architecture is to define the common interface(s) that the plug-ins themselves will implement. Say you have this interface definition in a common library:

public interface IPlugIn
{
    void DoSomething();
}

Then you define some implementations of that interface in other class libraries (the plug in libraries):

public class PlugIn1 : IPlugIn
{
    public PlugIn1(ILogger logger) { }

    public void DoSomething()
    {
        Console.WriteLine("PlugIn1 called");
    }
}

Note that this plug in has a dependency on some service (ILogger) that our DI container will know about.

Using the Container As the Plug-In Factory

Now all you need to do is use the ability to configure the Unity container through a config file to have the construction of those plug ins loosely coupled from the code.

Define the config info to configure the container with the plug in types, as well as the dependent types:

<configuration>
  <configSections>
    <section name="unity"
            type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,
                 Microsoft.Practices.Unity.Configuration, Version=1.2.0.0,
                 Culture=neutral, PublicKeyToken=31bf3856ad364e35" />

  </configSections>
  <unity>
    <typeAliases>

      <!-- Lifetime manager types -->
      <typeAlias alias="singleton"
           type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager,
               Microsoft.Practices.Unity" />
    </typeAliases>
    <containers>
      <container>

      <types>

        <type type="Common.IPlugIn, Common" mapTo="PlugIns.PlugIn1, PlugIns" name="PlugIn1"/>
        <type type="Common.IPlugIn, Common" mapTo="PlugIns.PlugIn2, PlugIns" name="PlugIn2"/>
        <type type="SomeDependencyLibrary.ILogger, SomeDependencyLibrary" 
              mapTo="SomeDependencyLibrary.Logger, SomeDependencyLibrary" >
          <lifetime type="singleton" />
        </type>
      </types>
    </container>
  </containers>
  </unity>
 </configuration>

Then just configure the container and resolve the plug-ins through a call to ResolveAll:

IUnityContainer container = new UnityContainer();
UnityConfigurationSection section = 
   (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
section.Containers.Default.Configure(container);

IEnumerable<IPlugIn> plugIns = 
    container.ResolveAll<IPlugIn>();
foreach (IPlugIn plugin in plugIns)
{
    plugin.DoSomething();
}

And viola. you have a simple plug-in factory using the container.

Wednesday, July 22, 2009 8:40:17 PM (GMT Daylight Time, UTC+01:00)
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Scott Bellware put together a great post emphasizing the importance of organizational productivity over developer productivity that I wanted to point people to and make some additional comments on. In his post, Scott points out the pitfalls of focusing only on developer productivity as a way to ship your product faster. He elaborates on the fact that if you don’t have a good quality-focused process and organization, the short term gains (or local optima as he describes them) created by developer productivity or efficiency tools may actually compound your problem in several ways.

Organizational Productivity

I totally agree with several things Scott points out in his post. First, a lot of the customers I deal with in consulting do have immature processes and organizations, so they need to fix those first and foremost if they really want to ship higher quality products faster. Following agile practices including the following are some of the minimum bars I think development teams should be targeting for most business applications:

• Practicing Scrum or having daily stand up meetings to facilitate team communications and collaboration
• Practicing Pair Programming or at a minimum having diligent code reviews on all production code
• Practicing TDD/BDD/DDD or at a minimum having a high degree of unit test coverage combined with a good loosely coupled design
• Documenting requirements in a light weight, but easy to understand and location form (user stories, bullet lists, work items all suffice if done coherently)
• Having a good CM process including good source control tools
• Having an automated build process that runs nightly at a minimum, or better yet trending to continuous integration

There is a lot more to having a good agile process in place than I can document here, but the point is that too many teams recognize that these are things they should be doing, but they never get around to establishing as a repeatable part of their process. Then they hear about developer productivity tools and think that just by using those, they will somehow overcome the organization-level lack of productivity with the micro-productivity enhancements that developer productivity tools can often have.

The Hazard of Developer Productivity Tools

Also as Scott points out, when used blindly, some developer productivity tools can actually cause grave damage to product-level productivity. One example of this includes some of the developer productivity tools in Visual Studio, specifically some of the code produced by designers and code generation. This has gotten better from version to version, but there is still the tendency to put things into Visual Studio that demo well and might be OK for toy applications, but should never be used for serious applications. For example, the SqlDataSource in ASP.NET encourages developers to drag and drop their way to a functional data driven page. Looks great, and you are done in minutes. Developer productivity nirvana. But what happens after that? You end up with hundreds of these scattered across your project, each with embedded markup tightly coupling the page to the database schema. Bad, bad, bad for overall productivity in developing a product because it is a maintenance nightmare. But these kind of features are often hyped in the VS demos as if it will make you able to ship your product so much faster. It might let you get a simple first version out the door faster. But even the first version of a moderately complex app will suffer in timeline as the schema changes throughout the development cycle and you have to keep tracking down the resulting breakage in the tightly coupled pages. The remedy is taking the time up front to put a good layered design in place, and use the right developer productivity tools in the right way (i.e. bind an ObjectDataSource to the domain objects coming out of a repository) to speed up the coding process slightly, but not end up with messy un-maintainable code from using them.

Another hazard I see with developer productivity tools (VS ones in particular) are that especially for less experienced developers, it tends to teach them that if they can’t do it through the tool, it can’t be done. I had this at a customer site the other day. We were using a mapping component, and the developer came in complaining something that we needed to do wasn’t supported by the component. After drilling into the problem, it turned out that what the developer really meant is “my Visual Studio integration for that component is not working, and if I can’t drag and drop it and hook things up in the designer, I have no clue how to code against the component itself”.

If you are going to use any developer productivity tool, the developers have an absolute responsibility for understanding what the generated code does, and how to write that code themselves if the tool is not available or is not doing things quite right. If they are going to use features that produce code that is not great for long-term productivity, they need to fix the code to make it more maintainable as soon as the code is generated. If fixing the generated code right then takes them longer than it would have to code it all by hand, then they shouldn’t be using the tool in the first place.

Another example is the WCF proxy generation in Visual Studio. While it is great for quickly the code in place to make calls to a service that exposes metadata, the proxy code that it generates is usually much more verbose than it needs to be, and it can totally garbage up your app.config or web.config file with unnecessary configuration elements that become your maintenance burden. It is usually more productive from an overall productivity perspective to do what we call “hand coding” the proxy.

The Benefit of Developer Productivity Tools and Why You Should Still Use Them - Correctly

However, that being said, I am a firm believer in not wasting developers time, as well as trying to keep developers focused on the logic they are implementing, instead of spending too much time banging on the keyboard and worrying about the structure of the code instead of its content. So even when I say “hand coding” above, I would prefer to use a developer productivity tool such as CodeRush + Refactor, ReSharper, or just Code Snippets in Visual Studio to output clean, templated code for those places where repetitive coding patterns are required. If possible, I would then look for opportunities to refactor some of that repetitive code into base classes or helpers, but that is not always possible.

So I actually often say that I firmly believe that every developer should have a copy of CodeRush+Refactor or ReSharper on their machine, and should spend a little time learning how to use the basic features of those products right. As Scott points out, doing so is not going to affect your overall timeline one bit if you don’t already have a highly efficient and streamlined organizational process. And if the developers don’t understand the code that is being spit out or when it is appropriate, it is again a liability , but that again comes back to professional responsibility of being a good developer.

But at a minimum, I do think the tools mentioned above save the developers tons of time in terms of not wasting time banging out snippets of code character by character, but instead lets them spit out the right code with minimal keystrokes. This frees their time and their mind to focus more on the logic of the code instead of the structure. It also lets them blaze through throw away implementation of prototypes and spikes much faster than if they didn’t have those tools, and if done right, that code is getting dumped once you figure out what you are going to do and how to do it anyway.

Using CodeRush/Refactor or ReSharper also tend to produce better consistency in the code, because if the tool templates are spitting the small structural elements out, those elements are more likely to be coded consistently across developers. Finally, both of those tools have great features for continuous refactoring of code to clean up things like redundant/unused declarations, replacing string concatenation with string.Format, and hundreds of other things that might otherwise be missed, or just take more time to do manually than they do using the tool.

Wrap Up

So bottom line, I agree with almost everything Scott says in his post. I just think in some places it paints an overly negative picture of developer productivity tools and could lead someone like a product manager to say “I don’t need to buy my developers these tools because they won’t help anyway”. If you don’t focus first at the process level, you still won’t ship your products any faster by using developer productivity tools. But I think with the right tools and the right approach to using them, you will still improve the quality of the code the developers are producing by using these tools, and that is worth it in its own right. And you may get through the experimentation implementation portions of your lifecycle a little faster as well.

But don’t fool yourself into thinking that just throwing these tools at the developer is all you need to do. And also approach any developer productivity tool with jaded optimism and get a real understanding of what it is producing and what the long term impact of that code is before you think it is really going to save you any time before committing to using it for production coding.

Sunday, July 12, 2009 11:19:24 PM (GMT Daylight Time, UTC+01:00)
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