Far too often we set up some kind of user friendly error handler, that sends us a copy of the error dump, but once our site goes live and is getting hit by hackers, and search bots, and having routine timeouts for whatever reason, we get deluged by so many emails that we just throw those errors into a folder and ignore them. But there's a better way! Learn how to set up a robust error handler that can send you lots of debug information while still handling issues like bots and hack attempts, commonly thrown errors you don't care about, secure information being included, and more. We'll also look at integrating our finished error handler with the excellent open source project Bug Log for further enhancing its capabilities and making it easier for individual users on the project to handle their subscriptions to receiving error reports from the site.

1. Don’t Ignore!
Your Error Messages
Mary Jo Sminkey!
CF Webtools

2. About Me
• 20+ Years in Web Development!
• ColdFusion Developer since CF 3.0 Release by Allaire!
• Author of the e-commerce application CFWebstore!
• Currently working for CFWebtools as the Lead Developer for a large e-commerce
website selling classic car parts (Classic Industries)!
• Hobbies include dog training and showing, photography, playing music,
baking, board games, scrapbooking, origami, and more!

3. There Will Always Be Bugs
• "If debugging is the process of removing software bugs, then
programming must be the process of putting them in." !
! – Edsger Dijkstra!
!
• “Programming today is a race between software engineers striving to
build bigger and better idiot-proof programs, and the Universe trying to
produce bigger and better idiots. So far, the Universe is winning.”!
! – Rich Cook

4. Dealing with Bugs
is Not FUN !
(But Necessary)

5. Developers Need To Be Brave

6. Classic Industries
• Large Ecommerce Site for Classic Car Parts!
• 3-4 million page views on average per month!
• Approx. 400K unique visitors!
• Averages 1-5 ColdFusion error reports per day

7. Why Are Bugs So Hard to Find?
• "We have a bug that occurs on the 31st of a month so once a month
we get a bug report. It gets assigned to a developer within 24 hours
who then fiddles for a bit before marking it 'unable to reproduce'." !
• Multiple OS/browser environments to test !
• Increasing use of javascript, Ajax, other client-side code!
• More complicated design patterns, use of frameworks, etc. versus
procedural code: !
• “There are two ways of constructing a software design. One way is to
make it so simple that there are obviously no deficiencies. And the
other way is to make it so complicated that there are no obvious
deficiencies."

8. Some Common Approaches to Error Handling
• CFTry/Catch !
• Global Error Handler (onError or cferror)!
!
• Display User-Friendly Message to User!
• Email Error Dump to Developer (maybe)

9. Common Problems with the Normal Approaches
• Hiding errors that we may need to know about (try/catch blocks)!
• Not enough information to figure out what happened to throw the error!
• Receiving errors from hack attempts, causing us to waste time that
should be spent tracking errors from legitimate users!
• Lots of copies of the same error, wasting time to determine which are
new errors and which are ones we’ve already reviewed!
• Errors that we know about and expect to receive regularly

10. Global Error Handler - onError or CFError?
• onError will not include ALL variable scopes!
• cferror will include all scopes (other than local vars, but we can deal
with that too)!
• This does mean you will typically need to need to keep your
Application.cfc tag based to some degree (pre-CF11). !
• Easiest is to put the cferror line in your OnRequestStart!
• We will often wrap the cferror in a conditional test for which
environments we want to show the CF errors versus using the error
handler. !
• We also want to disable the error handler for MXUnit tests

11. Same CFError Include
<cffunction name="OnRequestStart" returntype="boolean"> !
<cfif NOT ListFind( "local", application.environment) AND NOT !
! ! findNoCase("mxunit",cgi.script_name)>!
! <cferror type="exception" template="errorhandler.cfm">!
</cfif>!
….!
</cffunction>

12. Improving The Global Error Handler
!
• Remove any variable data internal to the error handler!
• Filter out errors from search bots!
• Allow use with try/catch blocks when we need to get data from the error !
• Skip common errors!
• Include all relevant variables scopes!
• Remove any secure data that is not safe to send via email!
• Clean the variable scopes so we don’t get data we don’t need!
• Process any data that might be encrypted or in some other format that
what is most useful for the developer to get!
• Don’t send lots of copies of the same error

13. ErrorHandler.cfm - Remove Vars used internally
!
• While this isn’t totally necessary, I don’t really care to see the
variables I create within the error handler itself in my error emails. !
• So rather than using variables scope directly, I create a struct that is
then used for all the local variables in the error handler, similar to how
we used to typically do local variables in CFCs. !
!
! <cfset localVars = structNew() />! !
! <cfset localVars.findBot = false />!
! <cfset localVars.findExclude = false />

14. ErrorHandler.cfm - Skip Errors from Bots
!
• You may prefer to receive these errors depending on your level of
error handling for malformed URLs and invalid params. !
• There are other more sophisticated ways to detect browser types
such as 3rd party plugins like Browser Hawk, but this is a simple way
to exclude most of the common ones. !
!
!

15. ErrorHandler.cfm - Skip Errors from Bots
!
<cfset localVars.botList = "bot,spider,crawl,jeeves,yahoo,slurp" />!
!
<cfloop index="localVars.item" list="#localVars.botList#">!
! <cfif FindNoCase(localVars.item, CGI.HTTP_USER_AGENT)>!
! ! <cfset localVars.findBot = true />!
! </cfif>!
</cfloop>!
!
<cfif NOT localVars.findBot>!
! Continue with error handler… !
</cfif>

16. ErrorHandler.cfm - Use for both cferror and cfcatch
!
• By coding the error handler to be available for use in a try/catch block we can drop
it into places in the code where we are having trouble debugging what is
happening, to get more information on the error. !
• This is particularly useful in CFC methods, where the global error handler won’t
have any data about the local vars. !
• The error structure we receive for global errors versus inside a cfcatch is different. !
• We need to detect these and set up variables for the areas in the code where we
are going to be outputting the error data. !
• When used in a cfcatch block, we may want to skip parts of the error handler, such
as displaying a user-friendly error message. !
!

17. ErrorHandler.cfm - Use for both cferror and cfcatch
!
<cfif isDefined("error.Diagnostics")>!
! <cfset localVars.errormess = error.Diagnostics>!
! <cfset localVars.errorData = error>!
! <cfparam name="request.errorType" default="fatal" >!
<cfelseif isDefined("cfcatch.message")>!
! <cfset localVars.errormess = cfcatch.message>!
! <cfset localVars.errorData = cfcatch>!
! <cfparam name="request.errorType" default="error" >!
</cfif>!
!

18. ErrorHandler.cfm - Skip Common Errors
!
• For some sites, you may have errors that you wish to detect due to them
occurring frequently and not being fixable. !
• How you handle them may vary based on your environment and other
detection methods for your sites (up-time detection, etc.) !
• For instance, for one client we frequently have database issues where lots of
timeout errors get thrown regularly. This is a known issue the client has
decided not to address at the time so while we log the number of times and
pages they occur on, we don’t need to receive emails for them. !
• We also ran into a bug where a malformed returnFormat in an Ajax call to a
CFC throws an error that can not be handled via other methods. !
!

19. ErrorHandler.cfm - Skip Common Errors
!
!
!
<cfset localVars.errorExcludeList = "Execution timeout expired,request has
exceeded the allowable time limit,Invalid returnFormat: jsPr”/>!
!
<cfloop index="localVars.item" list="#localVars.errorExcludeList#">!
! <cfif isDefined("error") AND FindNoCase(localVars.item, error.diagnostics)>!
! ! <cfset localVars.findExclude = true />!
! <cfelseif isDefined("cfcatch") AND FindNoCase(localVars.item,
cfcatch.message)>!
! ! <cfset localVars.findExclude = true />!
! </cfif>!
</cfloop>

20. ErrorHandler.cfm - What to Include
!
• What scopes you include will depend on your site and what types of
activities ColdFusion is doing. !
• We will also need to set up a list of “secure” variables that we are
going to want to exclude!
• If you want to scrub the data for sensitive data, typically you will want
to also create a list of scopes to scrub.!
!

21. ErrorHandler.cfm - What to Include
!
localVars.varstodump=“CFCATCH,ERROR,APPLICATION,ARGUMENTS,
ATTRIBUTES,CALLER,CGI,CLIENT,CFHTTP,FILE,FORM,REQUEST,
SESSION, COOKIE,THIS,THISTAG,URL,VARIABLES";!
!
localVars.varstoscrub=“ATTRIBUTES,ARGUMENTS,CGI,FORM,REQUEST,
SESSION,URL,VARIABLES,COOKIE,CFCATCH,ERROR";!
!
localVars.securevars=“CFID,CFTOKEN,JSESSIONID,SessionID,URLToken,
password,newpassword,customerID,ccName,ccNumber,cvv2,encryptkey";!
!

22. ErrorHandler.cfm - Creating the Error Dumps
!
• Now that we have our list of variables we want to output in our error logs and/or
emails, we’ll loop over the list and dump each scope. !
• We will do some special handling for some scopes. This will include those that we list
as potentially having secure information and scopes like Application that may have
data like a bean factory that we don’t want to output in error messages. !
• Your application may have specific error scopes that have their own special handling.
For instance, we set encrypted cookies for things like the customer ID on the site.
For the error handler, I decrypt that string so that I have the actual customer ID to
look up info in the database. Another example might be if I want to use the shopping
cart ID to include a dump of the actual shopping cart contents in the emails. !
!

23. ErrorHandler.cfm - Creating the Error Dumps
<cfsavecontent variable="localVars.dataDump">!
! !
! <cfloop list="#localVars.varstodump#" index=“localVars.loopItem">!
! ! !
! ! Code to parse and dump out the variable scopes here!!
!
! </cfloop>!
!
</cfsavecontent>!
!
!

24. ErrorHandler.cfm - Checking for CFC methods
!
• One thing I always want to exclude from error dumps are user-defined functions and
components.!
• If you use a bean factory like Coldspring or Wirebox, it’s usually just an easy matter of
excluding it in the appropriate scope dump. !
• If however, you have a collection of components and/or functions in something like
Application scope you may need to manually exclude it.!
• For components, you can use IsCFC() on CFLib.org written by Nathan Dintenfass.!
• For user-defined (or built-in) functions, use IsFunction() also on CFLib.org, written by
Ray Camden. !
• You can also use the showUDFs attribute on the cfdump tag itself. !
!

25. ErrorHandler.cfm - Sample Dump for Application Scope
!
<cfif IsDefined("#localVars.loopItem#") AND localVars.loopItem IS “APPLICATION">!
<cfset localVars.ApplicationVars = StructNew()>!
<cfset localVars.listExclude = "blogCache,errorLog" />!
<cfloop item="localVars.each" collection=“#Application#">!
<cfif NOT IsCFC( Application[localVars.each] ) AND NOT !
! ! ListFindNoCase(localVars.listExclude, localVars.each)>!
<cfset localVars.ApplicationVars[localVars.each] = Application[localVars.each]>!
</cfif>!
</cfloop>!
!
<cfset request.cfdumpinited=“false”>!
<cfdump var="#localVars.ApplicationVars#" label=“Application" showUDFs=“false”>

26. ErrorHandler.cfm - Sample Dump to Scrub Scopes
<cfelseif IsDefined("#localVars.loopItem#") AND ListFind(localVars.varstoscrub,localVars.loopItem)>!
<cfset localVars.ScrubbedVars = structNew()>!
<cfset localVars.scopeToCheck = Evaluate(localVars.loopItem) />!
<cfloop item="localVars.each" collection="#localVars.scopeToCheck#">!
<cfif ListFindNoCase(localVars.securevars,localVars.each)>!
<cfset localVars.ScrubbedVars[localVars.each] = "removed">! ! ! ! !
<cfelse>!
<cfset localVars.listremove = "GeneratedContent,CFCatch,CFError,Error,localVars,IsCFC">!
<cfif NOT ListFindNoCase(localVars.listremove,localVars.each) !
! AND NOT IsCFC(localVars.scopeToCheck[localVars.each]) !
! AND NOT structKeyExists(localVars.ScrubbedVars, localVars.each)>!
<cfset localVars.ScrubbedVars[localVars.each]= localVars.scopeToCheck[localVars.each]>!
</cfif>!
</cfif>!
</cfloop>!
<cfset request.cfdumpinited=“false”>!
<cfdump var="#localVars.ScrubbedVars#" label="Scrubbed #localVars.loopitem#” showUDFs=“false”>

27. ErrorHandler.cfm - Dump Remaining Scopes
<cfsavecontent>!
<cfloop … >!
<cfif … >!
Scrubbed var scopes!
<cfelseif IsDefined("#localVars.loopItem#")>!
<cfset request.cfdumpinited=“false”> !
<cfdump var="#localVars.ScrubbedVars#" label=“#localVars.loopitem#” showUDFs=“false”>!
</cfif>!
</cfloop>!
</cfsavecontent>!

28. ErrorHandler.cfm - Error Summary
<cfsavecontent variable="localVars.basicinfo">!
<cfoutput>!
<table width="100%" cellpadding="5" cellspacing="0" border="0">!
<cfloop collection="#localVars.errorData#" item="localVars.i">!
<cfset localVars.data = localVars.errorData[localVars.i]>!
<cfif IsSimpleValue(localVars.data) AND localVars.i IS NOT "GeneratedContent">!
<tr><td>!
<strong>#Ucase(localVars.i)#:</strong><br/>#localVars.data#!
</td></tr>!
</cfif>!
</cfloop>!
</table>!
</cfoutput>!
</cfsavecontent>

29. ErrorHandler.cfm - Swap Settings for Error Type
<cfswitch expression="#request.errorType#">!
<cfcase value="init">!
<cfset subject = "Error starting up #cgi.server_name#">!
<cfset errorMessage = "#cgi.server_name# was not able to start up.”>!
<cfset toAddr =“webmaster@cfwebtools.com" />!
</cfcase>!
<cfdefaultcase>!
<cfset subject = "Error on #cgi.server_name#">!
<cfset errorMessage = "An error has been encountered on #cgi.server_name#:”>!
<cfset toAddr = "errors@cfwebtools.com">!
</cfdefaultcase>!
</cfswitch>!

30. ErrorHandler.cfm - Eliminating Duplicate Errors
• We don’t need to get many copies of the same error via email!
• This makes it a lot harder to not only get an idea of how many different errors we have to
review, but takes time opening and loading each email to see if it is unique. !
• There’s different ways you can handle this but the easiest is to just log each error in the
application scope and then check it before adding new errors. !
• Typically I log each error only once every 4 hours, but you can use longer time frames
based on tracking multiple errors as follows. !
• By keeping a count of the errors we can check if multiple copies of the error are being
thrown. This can alert us to a critical situation on the server that may need to be
addressed immediately. !
• I also typically use this with some of the errors that are common and I don’t need to get
emails for single instances. !
• So we also want to track the number of times each error has been thrown in order to
generate an email every X number of times (I use 25).

31. ErrorHandler.cfm - Eliminating Duplicate Errors
<cfif NOT StructKeyExists(Application.ErrorLog, localVars.Errormess) !
! OR DateCompare( Application.ErrorLog[ localVars.Errormess ].TimeError, !
! DateAdd("h", -4, Now() ) ) LT 0 >!
! Generate Error Dumps Email here….!
<cfif request.errorType IS NOT "init">! ! ! ! !
<cfset Application.ErrorLog[localVars.Errormess] = TimeError: Now(), Count: 1 } />!
</cfif>!
<cfelse>!
<cfset Application.ErrorLog[localVars.Errormess].Count++ />!
<cfif Application.ErrorLog[localVars.Errormess].Count MOD 25 EQ 0>!
Generate Multiple Errors Email here….!
</cfif>!
</cfif>

32. ErrorHandler.cfm - Sample Email
<cfif NOT localVars.findExclude>!
<cfmail to="#toAddr#" from=“no-reply@cfwebtools.com“!
subject="#subject#" type="HTML">!
<br/><br/>!
#errorMessage#<br/><br/>!
#localVars.basicinfo#<br/><br/>!
<strong>Full message:</strong><br/><br/>!
#localVars.dataDump#<br/><br/>!
</cfmail>!
</cfif>

33. ErrorHandler.cfm - Sample Multiple Errors Email
<cfmail to="#toAddr#" from=“no-reply@cfwebtools.com“!
subject=“MULTIPLE ERRORS ON #subject#" type="HTML">!
<br/><br/>!
The following error has occurred
#Application.ErrorLog[localVars.errormess].Count# times in the last four hours
on #cgi.server_name#:!
#errorMessage#<br/><br/>!
#localVars.basicinfo#<br/><br/>!
<strong>Full message:</strong><br/><br/>!
#localVars.dataDump#<br/><br/>!
</cfmail>

34. ErrorHandler.cfm - Show User Friendly Error Page
• Based on the error type, we may or may not need to display a
message to the user (for instance, error in a try/catch block we most
likely will not)!
• We will first try to display a page using the full site template. !
• If that page itself errors out though, we should have a very simple
HTML only error page available as a fallback. !
• We also include analytics on the page itself to keep counts of
different types of errors encountered.

35. ErrorHandler.cfm - Show User Friendly Error Page
<cfif NOT ListFind("email,cfcatch", request.errorType)>!
<cftry>! !
<cfset action = "cferror">! !
<cfinclude template="/controller/linkcontroller.cfm" />!
<cfabort>!
!
<cfcatch type="any" >!
<cfinclude template="displayerror.cfm">!
<cfabort>!
</cfcatch>!
</cftry>!
</cfif>

36. ErrorHandler.cfm - Using in Try/Catch Blocks
• The error handler will be used automatically for any unhanded CF
errors. !
• However, one issue is that errors that occur inside CFCs will not include
the local scoped variables. !
• Therefore, you may want to use the error handler inside a try/catch
block particularly if you are trying to debug a specific error and need a
copy of the local variables. !
• In order to see what the local vars are set to at the time of the error, you
will need to copy them to another scope prior to calling the error handler. !
• We also use the error handler to notify us if there is some issue with
application initialization.

37. ErrorHandler.cfm - Using in Try/Catch Blocks
function name…. {!
try {!
code here that we need to debug….!
} catch (any err) {!
! //copy our local scope to request!
! request.functionLocal = Duplicate(local);!
! include “/views/errors/errorhandler.cfm”;!
}!
}!

38. Tracking User Actions - Page Tracker
• One thing that the error handler does not tell us is what the user might have
done to cause the error. !
• We only know what happened at best for that request, but there are times when
we may want to know the other actions the user performed prior to the error. !
• This can be particularly useful for errors thrown by Ajax requests, where we at
least want to know the page there user was on and what they did to generate
the Ajax call.!
• Since our application already makes use of sessions, it makes sense to log the
page requests into the session so that they automatically show up in the error
handler. !
• We also include this session object into support emails since users
typically do not include detailed information about what they were doing
when they ran into a problem.

39. Tracking User Actions - Page Tracker
function onSessionStart() {!
! //initialize the page tracker!
! session.pageTracker = arrayNew(1);!
}

40. Tracking User Actions - Page Tracker
function onRequestStart() {!
request.thisPage = cgi.script_name & '?' & cgi.query_string;!
if ( !arrayLen(session.pageTracker) IS 0 OR !
! ! session.pageTracker[1] IS NOT request.thisPage ) {! !
lock scope="session" type="exclusive" timeout="10" {!! ! ! !
if ( arrayLen(session.pageTracker) LT 20 ) {!
arrayPrepend(session.pageTracker,request.thisPage);!
} else {!
arrayDeleteAt(session.pageTracker,arrayLen(session.pageTracker));!
arrayPrepend(session.pageTracker,request.thisPage);!
}!
}!
}!
}

41. Tracking User Actions - User Info
• If you use sessions, you might find it useful to load data into the session that
can help you debug.!
• For instance, we typically put the user email, customer ID, and name into the
session when user logs in, even though this information is not otherwise used
from the session scope. !
• This not only helps in cases where we need to review related customer data
that might have caused the problem but that way we can also contact the
customer once we have corrected the customer. Nothing impresses your
users more than actually getting an email from your site telling them the
problem they ran into when they were trying to shop has been fixed! !
• We also include this session information into support emails that get sent
from the site, again since users have a tendency to do things like mistype
their email if we ask them to enter it.

42. BugLogHQ
• BugLogHQ is a free, open source CFML tool to centralize the handling of
bug reports for multiple applications. !
• It allows you to view, search, graph, report, and subscribe to bugs from
your applications. !
• However, BugLogHQ does not include all the variable scopes that my
global error can send out. !
• It does not typically include any scrubbing of the error data for possible
secure items.!
• Also, if you are sending every single error to it, you can overwhelm the
database with error entries, particularly if you are working with an
application that generates large numbers of errors, or cause an repetitive
bug in development.

43. BugLogHQ - Features
• BugLogHQ has a powerful Rules feature to set up email notifications of
errors, which include different rule types such as only the FirstInstance of
an error, specific error messages, or daily summaries of errors. !
• We find this particularly useful for clients where we often use different
developers on tasks, so that they can turn error reporting on and off as
needed. !
• You can also set BugLogHQ to purge its errors on a regular basis. !
• BugLogHQ can also run “heartbeat” monitors to check that your website is
running properly.

44. BugLogHQ - Installation
• Software and documentation found at http://www.bugloghq.com. !
• Runs on CF 8+ or Railo and mySQL or SQL Server. !
• Errors can be sent to BugLog using web service, HTTP post, or CFC call. !
• Includes clients for ColdFusion, Python, PHP and Javascript!
!
Application.cfc - onApplicationStart() :!
application.bugLogService = !
! createObject(“component", “buglog.client.bugLogService”).init(!
! bugLogListener = ‘http://buglog:8080/listeners/bugLogListenerREST.cfm’);!
! ! ! ! !

45. BugLogHQ - Usage in Error Handler
• To send all our variable scopes to BugLog, we need to have a single object
to include in the web service call. !
• Since BugLog already includes the error or cfcatch data, we don’t need to
include those.!
• We can also include an error type, which can be used as a filter in the
BugLogHQ reports.!
• I like to log even the errors that I typically don’t email on the first instance,
so that I still have some idea how often those are occurring.

46. BugLogHQ - Copying Variable Scopes
localVars.strScopes = structNew();!
….!
<cfdump var="#localVars.ScrubbedVars#" label="Scrubbed #localVars.loopitem#">!
<cfif NOT ListFind(“ERROR, CFCATCH”, localVars.loopitem)>!
<cfset localVars.strScopes[localVars.loopitem] = localVars.ScrubbedVars />!
<cfelse>!
<cfset localVars.errorData = localVars.ScrubbedVars>!
</cfif>!
…!
<cfdump var="#Evaluate(localVars.loopItem)#" label="#localVars.loopItem#">!
<cfset localVars.strScopes[localVars.loopitem] = Evaluate(localVars.loopItem) />!

47. BugLogHQ - Logging the Error
<cfif NOT localVars.findExclude>!
! … mail the error as usual!
</cfif>!
<!—- we check to make sure the bug log service is available (local dev) —->!
<cfif structKeyExists(application,"bugLogService")>!
<cfset application.bugLogService.notifyService(!
! ! ! localVars.errormess, !
! ! ! localVars.errorData, !
! ! ! localVars.strScopes, !
! ! ! request.errorType)>!
</cfif>

48. Debugging Javascript Errors
• Today’s applications typically have considerable javascript running on
them!
• jQuery, Bootstrap, AngularJS, and other libraries make sites more
feature rich and user friendly, but harder to debug remote client issues. !
• How then can we figure out what the cause of a user’s issue is when we
can’t see the Javascript error thrown by their browser? !
• BugLogHS does include a JS client but you will need to include it into
your JS code. !
• There are a variety of excellent 3rd party services you can use for
logging and tracking JS bugs.

49. Javascript Error Reporting Tools
• trackjs.com!
• qbaka.com!
• errorception.com!
• jslogger.com!
• muscula.com!
• exceptionhub.com!
• jserrlog.appspot.com (OSS)!
• github.com/occ/TraceKit

50. Mobile Error Monitoring Tools
These can be used to monitor and track mobile device errors. !
• bugsense.com!
• bugsnag.com

51. BrowserHawk
• BrowserHawk is an Enterprise-level tool for testing client environments
for requirements for your websites or website features.!
• It includes both a web service, and a JAR you can install on the server,
to use in ColdFusion pages to test and/or log information about the client
environment. !
• They also have a Javascript logging tool which works via webservice. !
• We have used BrowserHawk not just for testing compatibility for our site,
but to check for search bots prior to generating errors, as well as
including data about the client in support emails.

52. Questions?