Debugging: Resolving Errors
When it comes to
resolving errors, there are a variety of tags and techniques to assist
you. Some are features to help you while running a request to provide
additional information to track the program's state, while another is
the ability to do interactive step debugging, and the last are related
to getting system diagnostics. We don't have room to elaborate on
these, but do be aware of them.
Additional Info To Track Program State
The first
set of debugging tools, some of which are widely used while others are
still a surprise to many, are the debugging info enabled in the Admin
console, CFDUMP, CFLOG, CFTRACE, CFTIMER, and the cfstat command-line
utility (BlueDragon doesn't currently support the last two). Even
CFOUTPUT and CFABORT can be useful techniques when debugging.
These topics have been covered in more depth in the following articles
(and of course, the documentation):
There is also a new article this month related to the above: "Faster debugging with CFTIMER and CFTRACE", by Shlomy Gantz.
I'd also like to point out that BlueDragon offers a useful tag called
CFDEBUGGER to supplement those above. It traces all the lines of CFML
code executed in a given request, something that CF developers have
never had. I wrote about it in a past CFDJ article: CFDEBUGGER
(November 2003) http://coldfusion.sys-con.com/read/42101.htm.
Interactive Step Debugging
Of course, when some
think of debugging they immediately think of interactive "step"
debugging, and those folks have long complained that CFML lacked such a
capability (while some others don't miss it at all). As we went to
press, the folks at Fusion-Reactor.com (Intergral GMBC) released their
FusionDebug tool, which is an Eclipse plug-in that finally provides
step debugging for ColdFusion MX. Learn more at www.fusion-reactor.com/fusiondebug.
It's something I'm excited about. While many never knew it, we did
indeed have debugging available in ColdFusion 5 and before by way of
ColdFusion Studio (or today's HomeSite+). I've mentioned it in,
"Browsing within CF Studio/HomeSite+" (August 2003) http://coldfusion.sys-con.com/read/42061.htm. I even walked folks through using it in a 1999 presentation, available at www.systemanage.com/presentations/debugger-setup.pdf.
One reason I never wrote about it here is that it didn't always work.
Still, I'll point out that the official documentation, which many never
knew existed, was in Chapter 9 of Using ColdFusion 5 Studio at http://livedocs.macromedia.com/coldfusion/5.0/Using_ColdFusion_Studio/debug.htm. It should be possible to get it working with CF Studio and/or HomeSite+ with ColdFusion 5, if you still have them both.
System Diagnostics
Of course, sometimes to
understand error situations you need more information than just what's
reflected in running the current page. There could be other activities
or problems in the environment that are impacting your code. When it
comes to gathering diagnostics to understand and resolve problems, you
should consider taking advantage of the built-in logs, available in the
aforementioned ColdFusion logs directory. There's also an interface to
view them in the Admin console.
Beyond that, though, there's even more powerful analysis of what's
going on in your environment available by way of two commercial (yet
reasonably priced) tools that have come out in the past year or so:
SeeFusion at www.seefusion.com and FusionReactor at www.fusion-reactor.com. Both are available on a free trial basis so check them out.
There may be problems that are outside of ColdFusion that are affecting
you. Be sure to consider analyzing your Web server, database, network,
and the operating environment of the machine running ColdFusion. There
are logs and analysis tools for each that are beyond the scope of this
article. Finally, another vital tool when solving problems in CFML is
simply knowing what you should and shouldn't be doing in CFML. Don't
forget that you have documentation available at livedocs.macromedia.com
(no, the domain name hasn't changed yet). And more than just the CFML
reference, there's a 900+ page Developer Guide and more.
Testing: Preventing Errors in the First Place
While it's admirable to do a better job catching, handling, and
debugging errors when they occur, shouldn't we try to prevent them in
the first place? There are several ways you may be able to test your
code to prevent errors occurring at all, as we will discuss, ranging
from unit testing to syntax checking to validating your page input and
output.
Unit Testing
To prevent bad code from getting into
production many would recommend doing better unit testing, a subject
within the broader topic of test-driven development. CFML offers
various implementations of such unit-testing tools ranging from test
harnesses to cfunit and cfcunit, as discussed in:
Note that cfunit used to be part of the Developer Resource
Kit (DRK) but it's now available at the site above. There are still
other forms of testing to keep in mind.
CFML Syntax Checking
Since CFML isn/t a compiled
language, many errors slip by because we don't need to "run a compile
step" before releasing our code into the wild. We may have syntax
errors that would cause a page to fail as soon as it's run. How can we
catch them without actually running every page? Again, good unit tests
would help, but until you implement them, there's still another
approach.
Did you know that there are various means to check your CFML code's
syntax before releasing it? Since release 4, the Admin console has had
a mechanism that lets you point to a directory of code. It will analyze
your CFML and report if there are problems. While in CFMX it's formally
called a Code Compatibility Analyzer,
with a focus on checking code from previous releases, it also does CFML
syntax checking (see the "Advanced Options"). There has also been one
in CF 4 and 5. Note that you can point it at an entire directory (and
optionally recurse into subdirectories), so it's definitely something
to consider as a regular part of testing. See the online help in the
Admin console for more information.
Perhaps you're perturbed
that that tool is a Web interface requiring you to enter data in a
form. You want a command-line tool. I'm not aware of a means to call
that compatibility analyzer from the command line, but did you know
that CFMX 6.1 added a command-line precompile
tool? It's in the /bin directory as cfcompile.bat. While the primary
purpose is performance improvement (saving the auto-compile that takes
place on first load of the page into server memory), it will report if
there are any errors during evaluation of the CFML, so it can act very
much like the missing compilation step that other developers use to
catch errors early. Again, it is a command-line tool, and it does by
default compile all templates in a given directory.
See Chapter
5 of the CFMX 7 Administration manual (but not in the CFMX 6.1 manual)
for more information. It's also discussed in the following article.
Though the focus is on J2EE Web application deployment, the discussions
of cfcompile are still broadly useful: "Deploying Applications with
ColdFusion MX 7" (Dave Carabetta, March 2005) http://coldfusion.sys-con.com/read/48654.htm.
I'd like to point out also that I had discussed the benefits of such a
precompile tool in a two-part series. Though it was written before the
tool was released officially in 6.1, some of the info may still benefit:
Input and Security Validation Still another form
of testing to consider before you turn your application out for
production implementation is a range of tests that focus on ensuring
that the application avoids errors by preventing inappropriate input or
cross-site scripting as discussed in:
Output Validation Other forms of testing focus on
the output of your pages such as validating your HTML code
(accessibility checking, CSS validation, link checking, and spell
checking) as well as regression, load, and concurrency testing. I
covered all of these in "E-Testing: Debugging Your Projects" (October
2001)
http://coldfusion.sys-con.com/read/41816.htm.
Other Error-Related Topics
There are still other
topics that are tangentially (or perhaps directly) related to error
handling, including handling errors from CFMAIL, using the CFTHROW tag,
doing site monitoring, load testing, and leveraging version control to
manage your code better and recover from erroneous code releases.
Again, there's no room to elaborate, but I'll point out one more
article that covers a range of topics including error handling,
testing, and source control: "7 Habits of Highly Effective ColdFusion
Developers" (Robi Sen, February 2004) http://coldfusion.sys-con.com/read/43534.htm.
And while I'm mentioning error-handling articles, some will get value
out of a past article on handling errors in JavaScript: "Error Handling
in JavaScript" (Steve Bryan, October 2002) http://coldfusion.sys-con.com/read/41671.htm.
Finally, I'll also point out that in this month's issue there is an
article from Joshua Curtiss on yet another error-handling concept,
"Handling 404 Errors for a Migrated Blog".
I hope this trip through the archives of the CFDJ focusing on error
handling, debugging, and testing will help improve the quality of your
CFML development.
Subscribe to ColdFusion Developer's Journal Email News Alerts
Subscribe via RSS
