WEB342 Improved IIS Debugging Debug Diagnostics 1.0

1. WEB342Improved IIS DebuggingDebug Diagnostics 1.0 Chris Adams Web Platform Supportability Lead Web Platform & Tools Microsoft Corporation

3. Getting to know you… Are you a developer? Are you a IT professional? Hybrid?

4. Session Agenda • Introduction • Dig into crash scenarios • Understanding hangs • Investigating memory leaks • Debug Diagnostics extensibility • Session Summary

5. Introduction • Overview of Debugging: Past and Present • Integral tools for resolving Debug scenarios • Variables impacting Debugging

6. Overview • Past: offered many tools, fewer resolutions • Previous tools were often not server-ready • No single tool to address different debugging scenarios • Required expertise in debugging • Present: more advanced tools, still time-consuming to solve • Still lacks any analytical piece • Existing tools are not “integrated” into single tool • Do you really want to learn “debugging?”

7. Does this Scare you? Talking about tools… • There are several tools designed at resolving the same problems • As Windows Servers have grown, so have the debugging tools • Example of debugging tools

8. Variables Impacting Debugging • IIS is a “application platform” • The server is easily extensible • Extensibility examples include such things as proxy servers, publishing components, request handlers, and many, many more • Extensible platforms are robust but might be difficult to diagnose problems • Debugging is the worst-case scenario for any platform

9. Variables Impacting Debugging (2) • IIS’s Extensibility Examples • ISAPI • ASP.NET • Active Server Pages (ASP) • COM components • These “extensible” parts are often integrated and executing in same process

10. Crash Scenarios • Background of crashes • Defining and demonstrating crashes in worker processes: debugging crashes today • Using DebugDiag to quickly identify root cause of crashes

11. Background: Exceptions • What is an exception? • How do applications cause exceptions • What is a “handled” exception? • Unhandled exceptions need debugging and resolution Access Violation: C000 0005 Breakpoint Exception: 8000 0003 Stack Overflow: C000 00FD C++ exception: E06D7363 Managed exception: E0434F4D Invalid Handle: C000 0008

12. Background: Heap (2) • What is a heap? • Heap is a data structure • Heap Corruption: • Certain rules must be followed when using the heap • When rules are violated, heap corruption occurs • Heap corruption crashes • Code that corrupts heap is usually not the ones impacted

13. Debugging Crashes Today • Crash symptoms usually include a event in the event viewer • If Dr. Watson is enabled, crashes often create memory.dmp • Memory.dmp is a snapshot of the crashing process to be analyzed post-mortem

14. Debugging Crashes with Debug Diagnostics Kamal Balakrishnan Solutions Architect Microsoft IPTV

15. Hang Scenarios • Investigating the theory of “process hangs” • Debugging hangs today • Using DebugDiag to debug “process hangs”

16. Theory of “Process Hangs” • What is a process? • Memory boundary for execution of code • Allocated by Operating System done by calling CreateProcess or CreateProcessAsUser API • Processes do not execute code • Contains a minimum of 1 thread • What is a thread? • An independent sequence of instructions executing within a process

17. Theory of “Process Hangs” (2) • Thread implications on applications • The level of concurrency (virtual) is dictated by the number of threads • Real concurrency is dictated by the number of execution units • 1 processor = one or more execution units What are common thread pools for IIS? • ATQ thread pool • ASP thread pool • ASP.NET thread pool

18. Theory of “Process Hangs” (3) • ISAPI Extensions are recommended to implement custom thread pools • ATQ Thread pool is sensitive and high- performing • Blockage of threads in ATQ because of long execution can have harsh effects on IIS • ISAPIs often have long execution hence custom thread pools offload work from ATQ

19. Runaway Threads • A runaway thread is a thread stuck in a infinite (or near) loop • Performing a task that is consuming CPU • Either by design or because of error conditions • Runaway thread is taking CPU resources away from other threads • Often takes away from good threads • Causes performance degradation for server

20. SQL IIS Defining a Blocked Thread • A thread that isn’t using any CPU resources • Waiting on database calls to return • Waiting on web service calls to return • Waiting on a socket/network call to return • Waiting on a lock Thread 4 Thread 3 Thread 2 Thread 1

21. Locks and Deadlocks • What is a lock? • A synchronization mechanism to protect resources from being corrupted due to simultaneous access by multiple threads • Why do developers use locks? • Protecting data • Protecting other resources that are not memory based • Impact on applications if locks are poorly implemented • Causes threads to block • Can cause deadlock situations when using multiple locks in the application • Process hangs when no threads are available

22. Debugging Deadlocks and Process Hangs with DebugDiag Kamal Balakrishnan Solutions Architect Microsoft IPTV

23. Looking into Leaks… • What is a leak? • Types of Leaks

24. Leak Scenarios (2) • Why are leaks difficult to identify and resolve? • Server applications often cache memory allocations • The allocations are long term • These applications, to outsiders, look to have memory leaks • There are many other caches • Using Performance Monitor and seeing memory growth does not equal a memory leak

25. Leak Scenarios (3) • What are short-term allocations? • Memory expensive applications use “spike” allocations but are destroyed immediately after request (not long- sustaining) These are not Memory Leaks

26. Leak Scenarios (4) • Difference between cache and memory leaks? • Memory leaks are caused by unbounded allocations • Cache memory usage rises quickly, but tops out after application is stabilized

27. Nailing a Memory Leak in a Web Application using DebugDiag Kamal Balakrishnan Solutions Architect Microsoft IPTV

28. Extensibility of DebugDiag • Introduction to extensibility • DebugDiag architecture & object model • The role of scripts in DebugDiag • The role of extensions in DebugDiag • Customizing and extending DebugDiag

29. Extensibility of DebugDiag • DebugDiag has two ways to be extended • Data Collection • Analytical • Data Collection extensibility • Control Scripts • Both types of control scripts act as event handlers

30. Extensibility of DebugDiag • DebugDiag uses rules to generate scripts • Scripts can be modified and extended • All control scripts are written in VBScript • Scripts easily can interface and call into any automation compatible COM objects

31. Extensibility of DebugDiag • Analytical Scripts • Are written in “ASP+HTML” similar style • Are not processed by ASP.dll and does not have exposed ASP intrinsic • Scripts can be modified and customized based on environment • Base Object Model for Analytical Scripts • Base Object Model is consumed by the scripts • Entire object model can be extended

32. Extensibility of DebugDiag • DebugDiag will ship with a IIS-specific extension • This extension was written to the SDK specifications • This IIS specific extension provides all information needed about IIS for DebugDiag

33. Building and Using a Custom Extension for DebugDiag Kamal Balakrishnan Solutions Architect Microsoft IPTV

34. Session Summary • Debugging Live Web Applications without downtime is challenging • Web Applications are complex a integration of components from Microsoft, in-house development and third party vendors making it hard to isolate root cause of crashes, hangs and leaks • Crashes cause processes to terminate due to unhandled exceptions • Hangs are caused due to race conditions, lock contention, network blocking, database blocking, infinite loops and deadlocks • Leaks are caused by the failure to release memory allocated beyond typical short term allocations and caching • Debug Diagnostics has an extensibility model that allows it to successfully capture and analyze common debugging scenarios to determine the root cause

35. IIS Diagnostics Toolkit http://www.microsoft.com/windowsserver2003/iis/diagnostictools/default.mspx IIS Webcast Series http://www.iiswebcastseries.com TechEd IIS Sessions Remaining: Web340: Preview of IIS 7.0 3:45 PM – S330 Debug Diagnostics Cabana Session: Friday, June 10th - 10:45 AM to 12:00 PM Resources

36. IIS Debugging Week • Don’t miss the IIS Debugging Week in the IIS Webcast Series • Learn DebugDiag in more detail from the experts June 20, 2005 – June 24, 2005

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38. © 2005 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.