errgotrace

Error tracing for go programs

Finding the origin of errors in go programs can be really difficult, compared to other programming languages. There are projects like jujo/errgo that allow you to wrap errors before returning them and then get a stack trace for these. For that to work tough, you must use them consistently throughout your project and that won't help you with errors in 3rd party libraries or with errors that get handled and never get returned.

Errgotrace will add debug code to a go program that logs every returned error value (value that implements the error interface) and the function in which the error was returned. With that information it is usually easy to find the origin of errors.

Sample Output

This is what the output of a program compiled with errgotrace looks like.

[...]
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectKey: EOF token found
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectItem: EOF token found
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectKey: EOF token found
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectItem: EOF token found
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectKey: At 3:4: nested object expected: LBRACE got: ASSIGN
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectItem: At 3:4: nested object expected: LBRACE got: ASSIGN
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.objectList: At 3:4: nested object expected: LBRACE got: ASSIGN
2017/12/13 00:54:39 [ERRGOTRACE] parser.*Parser.Parse: At 2:31: literal not terminated
2017/12/13 00:54:39 [ERRGOTRACE] parser.Parse: At 2:31: literal not terminated
2017/12/13 00:54:39 [ERRGOTRACE] hcl.parse: At 2:31: literal not terminated
2017/12/13 00:54:39 [ERRGOTRACE] hcl.ParseBytes: At 2:31: literal not terminated
2017/12/13 00:54:39 [ERRGOTRACE] formula.parse: parsing failed
[...]

Usage

Please make a backup of your project before using errgotrace

To debug all go files in the current working directory:

$ find . -name '*.go' -print0 | xargs -0 errgotrace -w

To reverse the changes made to the go files:

$ find . -name '*.go' -print0 | xargs -0 errgotrace -w -r

CMD-usage:

Errgotrace modifies go files to include code for tracing go errors.

usage: errgotrace [flags] [path ...]
  -exclude string
        exclude any matching functions, takes precedence over filter
  -exported
        only annotate exported functions
  -filter string
        only annotate functions matching the regular expression (default ".")
  -r	reverse the process, remove tracing code
  -w	re-write files in place

Examples:
  Add tracing code to all go files in the current directory.
  $ find . -name '*.go' -print0 | xargs -0 errgotrace -w

  Add tracing code to all go files in the current directory.
  Exclude vendor dir.
  $ find . -path ./vendor -prune -o -name '*.go' -print0 | xargs -0 errgotrace -w

  Remove all tracing code from all go files in the current directory.
  $ find . -path ./vendor -prune -o -name '*.go' -print0 | xargs -0 errgotrace -w -r

Advanced Logging

If you need better/advanced logging just alter the code in log/log.go to your needs.

Credits

This project is inspired by and uses code from gotrace by James Bardin.