Debugging Go Programs with Delve

Transcript

1. Advanced Go Debugging with Delve Derek Parker Senior Software Engineer, Red Hat @DerkTheDaring
3. What makes Go different?
4. • Different execution model • Runtime / scheduler • Memory layout • Garbage Collector • Different type system • ...
5. Go runtime scheduler
6. Processor Thread Goroutine Scheduler Components P M G
7. Processor Thread Goroutine Scheduler Components P M G
8. Processor Thread Goroutine Scheduler Components P M G
9. Processor Thread Goroutine Scheduler Components P M G
10. Context Switching / Work Stealing
11. Context Switching
12. • Blocking syscall • Blocking IO • Function call (stack growth) • `runtime.Gosched` • Creating a new goroutine • ...
13. Work Stealing
14. Work stealing, cont’d P1 P2 T1 T3 T5 T2 T6 G4 G1 G3 G8 G9 Local queue Goroutines Threads Processors Global queue
15. Delve knows Go
16. [And now for something completely different]
17. Debugging Go programs
18. Go debug support
19. Improved DWARF information / debug support
20. • Better variable scope information • Ability to detect function arguments from return values • Better support for consts • Improved DWARF information when optimizations are enabled • Possibility of calling Go functions from Delve • Much more… (see `debugging` tag in issues)
21. Delve usage
22. $ dlv debug Type 'help' for list of commands. (dlv) dlv debug Begin typical debug session. Can optionally take package path.
23. $ dlv test Type 'help' for list of commands. (dlv) dlv test Begin debug session with test binary. Can optionally take package path.
24. $ dlv attach $pid Type 'help' for list of commands. (dlv) dlv attach Attach to running process
25. $ dlv trace <regexp> … [trace output] … dlv trace Begin tracing a Go program. Accepts regexp of functions to trace.
26. # Ensure correct ulimit for core dumps. $ ulimit -c unlimited # Run binary with correct env var. $ GOTRACEBACK=crash ./my-prog dlv core Debug core dumps from a Go process. Before trying, ensure system can produce core dumps: $ dlv core <binary> <path/to/core/file>
27. $ dlv replay path/to/trace dlv replay Debug Go programs using Mozilla RR
28. Thank you! Derek Parker Senior Software Engineer, Red Hat @DerkTheDaring