Grouping Crashes
Last updated
Last updated
Deciding which crashes your team should focus on can seem daunting. For many applications, it's impossible to investigate every crash. Fortunately, BugSplat automatically groups similar crashes, allowing you to concentrate your efforts on the bugs causing the most instability.
BugSplat's Summary page is a table of crash groups. Usually, crash reports are grouped by the top stack frame when the application crashes. However, sometimes the top of a stack contains common code that causes unrelated crashes to be grouped together. When this happens, auto-group rules can automatically select a lower stack frame that more accurately groups related crashes.
BugSplat has a set of customizable rules that skip over functions that are typically not interesting to application developers. Our default rules are designed to get you started quickly and can be modified as required for each crash report database.
The auto-group rules are pattern-based matching rules that skip irrelevant stack frames and create more meaningful crash groups. The three types of rules are group by, ignore, and ignore frames up to and including. Rules are defined per platform and can be specified to match either the function or file portion of the call stack.
You can view and change Auto-Group rules on the Rules page.
Let's look at how BugSplat groups a report with the Windows OS function KERNELBASE!RaiseException at the top of the stack. Our default rule is shown below:
By default, BugSplat groups crashes by the function at the top of the call stack. When BugSplat processes reports containing KERNELBASE!RaiseException at the top of the stack, the ignore rule matches and crashes will automatically be grouped by the following frame of the call stack. To group deeper in the call stack, you can combine multiple ignore rules. Alternatively, you can use ignore frames up to and including rules to group after a specified pattern that matches anywhere in the call stack. Ignore rules are useful for excluding frames that are known to be common error conditions.
Developers can also add rules that group by frames matching certain patterns. Group by rules are useful for including items that can be identified as belonging to your application. For example, you might choose group by to specify a file matching a path on your build machine, or a function matching your main application's module.
Auto-Group rules are matched via glob patterns. The following table describes common glob patterns.
*
matches any number of any characters including none
Law*
Law, Laws, or Lawyer
**
matches any number of path/directory segments. When used must be the only contents of a segment.
/**/some.*
/foo/bar/bah/some.txt, /some.txt, or /foo/some.txt
?
matches any single character
?at
Cat, cat, Bat or bat
at
[abc]
matches one character given in the bracket
[CB]at
Cat or Bat
cat or bat
[a-z]
matches one character from the range given in the bracket
Letter[0-9]
Letter0, Letter1, Letter2 up to Letter9
Letters, Letter or Letter10
[!abc]
matches one character that is not given in the bracket
[!C]at
Bat, bat, or cat
Cat
[!a-z]
matches one character that is not from the range given in the bracket
Letter[!3-5]
Letter1, Letter2, Letter6 up to Letter9 and Letterx etc.
Letter3, Letter4, Letter5 or Letterxx
Auto-group rules are processed in a specific, consistent order that cannot be changed. The rules engine follows the logic below:
If there are any group by rule matches, select the top-most matching frame as the candidate frame. Use the resulting frame for grouping. Don't process any more rules.
If there are any ignore frames up to and including rule matches, select the lower-most matching frame as the candidate frame. Starting with the candidate frame, skip over any frames that match the ignore rules until a frame that doesn't match any ignore rules is found. Use the resulting frame for grouping. Don't process any more rules.
At this point, neither group by nor group after rules matched any stack frames. The rules engine will apply the ignore rules starting with the top stack frame, skipping over any frames that match the ignore rules until it finds the first frame that isn't to be ignored. The resulting frame is used for grouping.
When you specify a new Auto-Group rule, it will be applied to newly processed and reprocessed crashes only. If you'd like to batch reprocess crashes to apply new rules, please contact Support.
BugSplat can also ignore specific parts of the call stack when creating groups. By default, BugSplat will group items that match based on function name only. At the top of the Rules page you'll find the options include module name, include line number, and include address offset. Enabling these settings will include the respective properties in the group calculation.
The module name is the name of the library or executable that added the frame to the stack. The line number is the line of source code where the function crashed, and the address offset is the instruction pointer offset. The hex offset is only considered for grouping stack frames that are not symbolicated.
With all settings enabled, groups would be created by a match on the entire string MyConsoleCrasher!Crash(42), where MyConsoleCrasher is the module name, and 42 is the line number. A group would also be created by a full match on the unsymbolicated frame MyConsoleCrasher!Crash+0xfff, where 0xfff is the address offset. With all options disabled groups would be created by a match on just the function name Crash.
The Crashes page displays a list of reports and their associated group under the Stack Key column. We've added a rule that effectively skips KERNELBASE!RaiseException and the reports are now grouped by the next frame in the stack MyConsoleCrasher!_CxxThrowException(75). To see the report's stack trace, click the value in the ID column.
On the Crash page, scroll down to the list of stack frames for the crashing thread. Notice that we didn't quite get our grouping rules correct. Our rules have caused the report to be grouped under the function in bold, MyConsoleCrasher!_CxxThrowException. The function we actually want to group on is MyConsoleCrasher!ThrowByUser. Expand the row containing MyConsoleCrasher!ThrowByUser to reveal the Group Rules button.
We can click Group Rules and add another rule that ignores frames up to and including stack frames where the function matches the glob *_CXXThrowException*. After creating this rule and reprocessing the crash report, you will see the correct grouping.
Once new grouping rules have been applied, navigate to the Summary page to view an overview of groups in the selected database. The Summary page provides report counts for all of the various groups. Targeting groups with the highest report Count will generally give teams the best return on their efforts. Another interesting metric to target is Users Affected, which represents the number of unique users that ran into a specific problem during the selected time frame.
