Reporting Services From The Command Line

Monday, January 31, 2005 by scott
0 comments

This past week I managed to:

  • Shovel snow
  • Catch a cold
  • Sleep for 16 hours on a Saturday
  • Model the process of cross matching blood specimens to blood units for transfusion with a database schema.
  • Meet various other work related hard deadlines…

All of this fun activity didn’t leave much time for:

  • Blogging

This evening I finally got to jump back into a Reporting Services frame of mind in preparation for San Fran next week. Reporting Services ships with a utility to run “scripts” from the command line: the rs (rs.exe) utility. Most Microsoft server applications expose a COM object model that admins can script against using VBScript, but Reporting Services exposes only a web service API. The “scripts” that rs.exe executes are actually little hunks of VB.NET code that invoke methods on the web service API.

Reporting Services only ships two sample scripts. One script cancels running jobs on the server (CancelRunningJobs.rss), the second script (PublishSampleReports.rss) demonstrates how to deploy reports to the report server (yes, the default extension is unfortunately “rss”). A really short script might look like the following:

Sub Main() 
  Dim permissions As String() 
  permissions = rs.GetSystemPermissions() 

  For Each permission As String in permissions 
    Console.WriteLine(permission) 
  Next 
End Sub 

I can save the above snippet in a text file and execute the instructions from the command line like so:

rs -i scriptname.rss -s http://localhost/reportserver

The rs utility compiles the above snippet (without option strict, so there is no need to declare permissions with a specific type) and executes the code. Obviously, there is some additional infrastructure in place to let the variable rs invoke web service methods. A little poking around with reflector reveals the utility sets up our code with imports for the System, System.Web, System.WebServices, System.WebServices.Protocols, System.IO, and Microsoft.SqlServer.ReportingServices namespaces. The utility wraps the code chunk shown above inside of a class declaration (____ScriptClass) and adds a member variable (rs) defined as type ReportingService.

What’s also interesting is an embedded resource in rs.exe by the name of StartupClass.vb. The StartupClass, stripped down to essentials (I removed the code for exception handling and for batching commands in the script.), looks like the following:

Public Module MainModule 

  Public Sub Main(ByVal args as string()) 

    Dim rs as new WebServiceWrapper(args(0), args(1), args(2), args(3)) 
    Dim clientScript as new ____ScriptClass() 
    clientScript.rs = rs 
    clientScript.Main() 

  End Sub 

End Module 

What intrigues me about rs.exe is how easy it is to pull off this “scripting” technique in .NET. Think about what it would take for an application to pick up a hunk of C++ source code from the disk and just execute it in-process. It is possible, of course, but fraught with peril.

The tricks you can pull off safely in .NET just never cease to amaze me.

Funny Numbers In My Stack Trace

Tuesday, January 25, 2005 by scott
4 comments

Someone in the newsgroups recently asked what the numbers mean in a release mode stack trace. For instance, what can you do with the following information?

[NullReferenceException: Object reference not set to an instance of an object.]
   aspnet.debugging.BadForm.Page_Load(Object sender, EventArgs e) +34
   System.Web.UI.Control.OnLoad(EventArgs e) +67
   System.Web.UI.Control.LoadRecursive() +35
   System.Web.UI.Page.ProcessRequestMain() +720

The stack trace gives us a little bit of information to go on, at least we can narrow the problem down to a specific method inside of a specific type, but +34 doesn’t seem to be particularly helpful – what does it mean? There are two answers to this question.

The first answer is: don’t worry about it. To narrow the source of the exception down to a single line of code, just build with debugging information (Project -> Properties -> Configuration Properties -> Build -> Generate Debugging Information). You should now have a PDB file output alongside your release mode assembly. With a PDB in place the runtime can give you a line number close to where the exception occurred.

 
[NullReferenceException: Object reference not set to an instance of an object.]
   aspnet.debugging.BadForm.Page_Load(Object sender, EventArgs e) in 
e:\dev\xprmnt\aspnet\debugging\badform.aspx.cs:16
   System.Web.UI.Control.OnLoad(EventArgs e) +67
   System.Web.UI.Control.LoadRecursive() +35
   System.Web.UI.Page.ProcessRequestMain() +720

The above answer is the practical answer, but it doesn’t satisfy the curious person who insists that all numbers have a meaning and a purpose. +34 isn’t some random number the runtime spits out after sampling the microphone input - so where does it come from?

For reference, the Page_Load method looks like the following:

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
 
namespace aspnet.debugging
{
   public class BadForm : Page
   {
      protected Label Label1;
   
      private void Page_Load(object sender, EventArgs e)
      {         
         if(!IsPostBack)
         {
            string s = null;
            Label1.Text = s.Insert(0, "foo");
         }  
      }
 
      #region Web Form Designer generated code …
   }
}

We already know +34 doesn’t refer to a line of code. So perhaps the number refers to an offset into the IL instructions? Here is what ILDASM shows as the instructions for Page_Load.

.method private hidebysig instance 
void  Page_Load(object sender,
                class [mscorlib]System.EventArgs e) cil managed
{
  // Code size       34 (0x22)
  .maxstack  4
  .locals init ([0] string s)
  IL_0000:  ldarg.0
  IL_0001:  call       instance bool [System.Web]System.Web.UI.Page::get_IsPostBack()
  IL_0006:  brtrue.s   IL_0021
  IL_0008:  ldnull
  IL_0009:  stloc.0
  IL_000a:  ldarg.0
  IL_000b:  ldfld      class [System.Web]System.Web.UI.WebControls.Label aspnet.debugging.BadForm::Label1
  IL_0010:  ldloc.0
  IL_0011:  ldc.i4.0
  IL_0012:  ldstr      "foo"
  IL_0017:  callvirt   instance string [mscorlib]System.String::Insert(int32,
                                                                       string)
  IL_001c:  callvirt   instance void [System.Web]System.Web.UI.WebControls.Label::set_Text(string)
  IL_0021:  ret
} // end of method BadForm::Page_Load

No, 34 bytes puts us beyond the end of the IL instructions.

Let’s go one level lower into native code. Using WindDBG and SOS, it’s easy to view a disassembly of Page_Load after the JIT compiler has partied on the method. I use WinDBG to attach to the asp.net worker process after the page has executed and do a .load sos for managed debugging.

To view a disassembled method, you first need the address of the MethodDesc structure for the method, which name2ee can yield (aspnet.dll is the unfortunate name I gave my assembly):

!name2ee aspnet.dll aspnet.debugging.BadForm.Page_Load
--------------------------------------
MethodDesc: 1b873a0
Name: [DEFAULT] [hasThis] 
Void aspnet.debugging.BadForm.Page_Load(Object,Class System.EventArgs)

Now pass the address to the (u)nnassemble command.

!u 1b873a0
Normal JIT generated code
[DEFAULT] [hasThis] 
Void aspnet.debugging.BadForm.Page_Load(Object,Class System.EventArgs)
Begin 07f805b8, size 52
07f805b8 55               push    ebp
07f805b9 8bec             mov     ebp,esp
07f805bb 83ec10           sub     esp,0x10
07f805be 57               push    edi
07f805bf 56               push    esi
07f805c0 53               push    ebx
07f805c1 8955f8           mov     [ebp-0x8],edx
07f805c4 8bf1             mov     esi,ecx
07f805c6 33db             xor     ebx,ebx
07f805c8 8bce             mov     ecx,esi
07f805ca e819a8fef9       call    01f6ade8 (System.Web.UI.Page.get_IsPostBack)
07f805cf 0fb6f8           movzx   edi,al
07f805d2 85ff             test    edi,edi
07f805d4 752a             jnz     07f80600
07f805d6 33db             xor     ebx,ebx
07f805d8 8bbec4000000     mov     edi,[esi+0xc4]
07f805de ff357c40f906     push    dword ptr [06f9407c] ("foo")
07f805e4 8bcb             mov     ecx,ebx
07f805e6 33d2             xor     edx,edx
07f805e8 3909             cmp     [ecx],ecx
07f805ea ff1564ddb779  call dword ptr [mscorlib_79980000+0x1fdd64 (79b7dd64)]
                         (System.String.Insert)
07f805f0 8945f0           mov     [ebp-0x10],eax
07f805f3 8b55f0           mov     edx,[ebp-0x10]
07f805f6 8bcf             mov     ecx,edi
07f805f8 8b01             mov     eax,[ecx]
07f805fa ff9094010000     call    dword ptr [eax+0x194]
07f80600 90               nop
07f80601 5b               pop     ebx
07f80602 5e               pop     esi
07f80603 5f               pop     edi
07f80604 8be5             mov     esp,ebp
07f80606 5d               pop     ebp
07f80607 c20400           ret     0x4

The method starts at address 07f805b8. Moving 34 bytes into the method lands us on the ‘cmp [ecx], ecx’ instruction. CMP is an x86 opcode for compare, which seems like an odd thing to do until you realize the funny quirks of assembly language. For instance, earlier in the method you’ll see xor edx, edx. This instruction isn’t really trying to do an exclusive OR operation (XOR). Instead, this is an old trick used to set the EDX register to 0 in the fastest manner possible: by XORing the register against itself. The more obvious “mov edx, 0” (move 0 into edx) might cost an extra half nanosecond on a 3 GHz machine.

What the cmp instruction is doing here is carrying out part of the IL’s callvirt contract (referring to the IL you’ll see we do a callvirt to the String.Insert method). We can see in the dissasembly the next instruction calls the Insert method. callvirt is documented as throwing a NullReferenceExcecption if the object reference for the instance method you want to call is null. To make a long story a tad shorter: the ecx register contains the this pointer for the string instance that we want to call Insert on, and cmp [ecx], ecx generates a compact, 2 byte instruction to check ecx for null by dereferencing the ecx register. When the instruction dereferences the null pointer in ecx – program go boom.

In conclusion, +34 does have a meaning – it’s an offset into the native instructions for the method. Debugging at the assembly level doesn’t make any sense because you should always have PDBs available, but at least we can all sleep at night knowing the number 34 holds some meaning … somewhere.

You Want To Be An Architect?

Monday, January 24, 2005 by scott
4 comments

I was flipping through SDTimes this week and came across the article “Turning Architecture Into a Profession”. The Open Group intends to begin a certification program for software architects.

“While declining to discuss specifics of the program just yet, de Raeve did say architects will have to show they have a body of experience and that they’re capable of deploying an as-yet-undefined set of skills in the delivery of systems architectures in real-world situations. Among those skills are communication, conflict resolution, architecture modeling techniques, and the ability to apply methodologies and elicit shareholder requirements, he said.”

Hmm, conflict resolution.

Do you think there will be a standardized test?

I wonder what such a test would look like…

 

Section II: Conflict Resolution

Please review each question carefully and select the single, best answer available.

1. Harry says the company needs to standardize on a language with curly braces. Fred says he hates curly braces, and is in the parking lot with a screwdriver threatening to flatten the tires of curly brace fans. What do you do?

a) Give Fred more screwdrivers.
b) Get your car safely out of the parking lot while dialing the police.
c) Take Harry and Fred to lunch and discuss the aesthetics of braces.

2. The CEO has barged into the office demanding the company’s flagship product be “SOA compliant” in time for the next tradeshow. What do you do?

a) Call in a consultant.
b) Have the CEO buy lunch and discuss.
c) Tell the CEO you can get the software to level V SOA compliance, but you'll need a bonus.

3. Jill says the opening curly brace goes on the next line. Jack says the opening curly brace stays on the same line. What do you do?

a) Call a meeting and take a vote.
b) Adjust Jack’s thinking with a heavy, blunt object.
c) Switch to Python

4. Harry refuses to work on the new project because it’s not using domain driven design. Fred is threatening the tech writers with a screwdriver. Jack refuses to write unit tests, and Jill says your architectural diagrams look like the work of a five year old. What do you do?

a) Something is wrong? This is a good day.
b) Start a job search.
c) Lock the door and reach for some of the liquid stress reliever in the bottom drawer of your desk.

This concludes Section II.

P.S. The correct answers were B, B, B, and B.

Source Control Cost Me $1.2 Billion

Friday, January 21, 2005 by scott
1 comment

Perhaps I've overstated the title for dramatic effect, but as a taxpayer I've certainly donated some amount of money to failed software projects for the U.S. government. I’d be curious to see a post-mortem report on some of these projects to hear what went wrong. I’m sure the list could go on and on.

Of all the agencies though, certainly NASA has the toughest job. I mean, you forget to put one tiny file into version control, and oops, $1.2 billion down the drain. I write about this story in the latest OdeToCode article - “Source Control: A Primer”.

The NASA story came to mind this week when I interviewed some candidates who work for consulting shops. Not only did one or two never use source control, but they asked what purpose it served. Hopefully, the article will reach out and touch a few people.

An Ad, a Thought, and a Threat

Tuesday, January 18, 2005 by scott
5 comments

Ad for the day

When I first heard of an open source project by the name of DotNetNuke, I really thought I’d be looking at the source code to a first person shooter. As it turns out, DNN is everything one needs to run a website. Now there is a book dedicated to DNN ready to hit the market from my friends at Packt Publishing.

Thought for the day

I was listening to a Stephen Hawking recording during the commute today and he said: “Imagine now a star with the mass ten times the mass of the sun”. I tried. I failed.

Threat for the day

One more burst of comment spam and this blog gets a CAPTCHA control. Any objections? Any alternatives? Who are these people and why can't we stick them with sharp pins?

CLR & OS Independence

Monday, January 17, 2005 by scott
0 comments

A storm brews on the distant horizon around the delivery of Longhorn and the Future Of of Assembly Versioning. Rocky Lhotka and Kent Tegels feel the versioning strategy coming down the road will stagnate Microsoft’s version of the .NET runtime. I wasn’t too alarmed by the article on the ServerSide.NET for a few reasons.

First, to some extent, development life on Windows has followed this course and thrived for sometime. The Win32 API has been the foundation of the platform and changes come relatively slowly with major OS releases and service packs. On top of the API assorted runtimes and frameworks (like MFC and the VB runtime) made developers more productive by encapsulating and enhancing the platform. These platforms could provide some amount of innovation, but major revolutions were almost impossible without support from new features in the underlying platform. It’s not always a bad thing to say the foundation is stagnant, though. After all, I wouldn’t feel comfortable if System.Object were sprouting new methods every year.

Secondly, I know what you might be saying: “Just because it’s always been that way doesn’t mean we can’t have a better solution”. Yes, this is true. In fact, the above approach is the approach in theory only. In practice, changes come as needed and when the demand is present. Remember the NT 4 Option Pack? The option pack shoehorned a distributed application platform (IIS, message queuing, transaction server) into a one year old operating system while Windows 2000 was still cooking in the oven. How about the foundational pillar of Longhorn known as Avalon that suddenly appeared on XP machines around the world?

Finally, wherever Microsoft stagnates, competition finds a niche. Just look at Firefox and search tools over the last 12 months. Competition forces Microsoft into innovation – and they always find a way to stay competitive. The competition in the common language runtime arena is here already. I'm not worried yet.

CSS & Me

Friday, January 14, 2005 by scott
3 comments

Every so often I take a look at an application and think, hmmm, with a couple tweaks I could have this UI looking really nice, but when I go to check-in the style sheet changes I realize I only have read-only access. Then I remember - after my last set of tweaks they revoked my commit privileges on all css files. Sigh. The measures people take when they don’t agree with your sense of color and style.

Over the years I’ve recognized the flexibility style sheets offer, and I’ve designed (in the architecture sense) with css in mind. Still, I’ve never felt completely comfortable with css, partly because I have nightmares of looking at bug tracking entries circa year 2000. You know, the entries that look like “Fonts are offset 1 pixel to the left on browser version 4.35.7654.2 when system time between 1300 and 1315 hours.”. Since one big customer has an affinity for browser version 4.35.7654.2 it’s time to tell a dev to work around another CSS quirk and re-test on 18 browser versions. Today, Google turns up over 300,000 hits for “yet another css bug” – yikes.

Another problem is digging into the CSS files someone else wrote. It can prove difficult to piece together what I’m seeing on the screen with the styles in a css file. A great tool to help put this type of puzzle together is the web developer extension for FireFox. Is there anything comparable for IE?

Finally, CSS files never seem to shrink – they only grow bigger. New styles are added, old styles never disappear. Someone needs to write some sort of refactoring / optimization tool for CSS. Or have they already?

Not that I’d be able to use the tool, seeing as how I’m banished from styleland.

Course I do have the admin password to use in a pinch….

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