eXtreme Debugging with apologies to Kent Beck, et al

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eXtreme Debugging!(with apologies to Kent Beck,
et al)

• David T Watts
• CTO
• Fig Leaf Software
• 30 Jul 2000

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What is eXtreme Debugging?

• For the purposes of this demonstration, its
  debugging problems external to CF.
• Many common problems cant be identified from
  within CF.
• This presentation will examine how to solve
  common problems using third-party freeware and
  shareware tools.
• This presentation focuses on NT, but there are
  analogues for Solaris, etc.

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What well look at

• OS permissions problems
• HTTP FTP protocol problems
• Problems with external DLLs
• Testing COM objects
• Help Resources

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OS permissions problems

• Most commonly encountered when using IIS to
  control access via file ACLs
• Examplevirtual server authentication
• ProblemMultiple web server authentication
  prompts after several tries, access is allowed,
  but application doesnt work correctly.

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Permissions problems, contd

• Cursory glance at directory ACLs looks correct
  authtest1 allows anonymous user, authtest2 allows
  DAVE\Users

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Permissions problems, contd
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Permissions problems, contd
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Permissions problems, contd

• For a quick determination of file ACL problems,
  you can use the freeware NT File Monitor, from
  www.sysinternals.com. Registry permissions
  problems can be diagnosed with the NT Registry
  Monitor, also freeware.

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Permissions problems, contd
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HTTP FTP protocol problems

• Some problems between client and server require
  viewing raw headers and data.
• Problems may occur between end-user and server,
  or between one server acting as a client and
  another server.

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HTTPAnalyzer

• HTTPAnalyzer is a freeware Windows tool from
  http//www.coolfusion.com/ which shows HTTP
  request and response headers. Easy to use and
  effective for simply looking at headers.

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HTTPAnalyzer
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Telnet

• Telnet is available on practically every
  TCP/IP-networked computer.
• Telnet can be used to build custom HTTP requests
  and view and log responses.
• Some telnet clients can be scripted.

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Telnet
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Netcat

• Common Windows telnet clients dont work very
  well, and cant be scripted.
• Netcat, available for NT from http//www.l0pht.com
  /weld/netcat/ can be used to perform the same
  tasks as telnet, and more.
• Netcat can redirect to and from files, and can be
  used to act as an HTTP client or server.

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Netcat, contd

• Netcat usagenc switches IP addr/host port
• Switches-d detach from console-e execute
  (followed by command)-l listen-L listen and
  restart after termination-p listening port-t
  perform telnet negotiation-v verbose

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Netcat, contd

• Using Netcat as a client This example pipes a
  text file of HTTP request headers to Netcat.

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Netcat, contd
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Netcat, contd
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Netcat, contd

• Netcat can also be used as a server this is
  useful for determining problems with file uploads
  and proprietary plugins. In this example, Netcat
  will return an HTTP response to any request on
  port 81.

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Netcat, contd
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Netcat, contd
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Recording proxies

• Recording proxies allow the easy capture of
  multiple requests/responses between client and
  server.
• Typically, a recording proxy requires that you
  modify the request to pass through the proxy.

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Recording proxies, contd

• Freeware HTTP and FTP recording proxies are
  available from http//www.compansr.demon.co.uk/.
  These proxies are Perl scripts, and require that
  Perl be installed on the machine that will act as
  the proxy (typically the requesting client).
• These scripts record request headers, but not
  request bodies.

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Recording proxies, contd
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Recording proxies, contd
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Recording proxies, contd

• Load-test tools can also generally be used as
  recording proxies this is often how the load
  test script is created. These will record headers
  and bodies.

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Working with external DLLs

• A DLL, such as a CFX component, working on one
  machine may not work on another for no apparent
  reason.
• Typically, this is caused by a dependency on a
  library found on the working machine, but not on
  the other.

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External DLLs, contd

• You can use Dependency Checker (depends.exe) to
  determine what files are needed.
• Dependency Checker is available in the Windows NT
  Resource Kit, Windows 2000 Support Tools (on the
  Win2K CD), and in Visual Studio.

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Dependency Checker
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Testing COM objects

• Many, but not all, COM objects can be used from
  CF.
• COM objects often come with ASP sample code, but
  this ASP code may hide some of the complexity
  behind the objects usage (ex authentication).
• To separate object testing from web server
  issues, use Windows Script Host to automate the
  object, then convert the WSH test to CF
  iteratively.

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Testing COM objects, contd
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Help resources

• Beyond the standard resources for CF, there are
  several that are useful to CF developers on NT.

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Help resources, contd

• Windows NT/Windows 2000 Resource Kits
• IIS Resource Kit
• Windows 2000 Magazine Archive, available on CD
  http//www.win2000mag.com/
• MSDN Library, available from Microsoft
• Microsoft Online Support http//support.microsoft
  .com/

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General advice (a.k.a. common sense)

• Many problems require an approach outside of the
  normal CF development process.
• Very few problems, however, are new to you! Most
  of them have existing solution processes.
• Sometimes, the solution to a problem requires
  recasting the problem to a different problem
  domain in other words, looking at the process
  (What am I trying to accomplish?) rather than
  the implementation issues (how do I do x?).

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General advice, contd

• A competent CF developer needs to know more than
  just CF and SQL.
• Beyond development skills, CF developers need to
  have a basic understanding of the OS theyre
  using, TCP/IP networking, and the HTTP protocol,
  among other things.
• Iterative solutions make problem-solving easier.
• Problems that are purely CF problems can easily
  be tested by any competent CF developer.

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Thats all, folks!

• This presentation will be available Monday from
  the CFUG section of the Fig Leaf site, and should
  be available from the CFUN2K site as well.
• If there are any questions, please contact Dave
  Wattsdwatts_at_figleaf.com
• Thanks, and have a nice day!