delve-debug-sample

README

delve-debug-sample

sample for debugging with delve

how to use

Run main.go with delve debugger. Make sure build binary with optimizations disabled.

$ go build -gcflags "-N -l" main.go
# -N    disable optimizations
# -l    disable inlini
$ dlv exec delve-debug-sample

(dlv) continue
2020/02/15 21:03:10 start server

# other terminal
$ curl localhost:12000/foo

set conditional breakpoints

you can define conditional like below

(dlv) break main.go:59
(dlv) condition 1 k==10

show goroutines

break at line below

log.Println("goroutines dispatched")

you can see main.fooHandler.func1, main.fooHandler.func2 goroutines.

coredump

Unfortunately, dlv core is only supported with linux, windows now.

For testing dlv core on MacOS, use dockerimage

# build centos8 container
docker build -t centos8-gdb .

# build for linux
GOARCH=amd64 GOOS=linux go build -gcflags "-N -l" .

# run with security option to use ptrace
docker run --rm --cap-add=SYS_PTRACE --security-opt seccomp=unconfined \
  -it -v ${PWD}:/delve-debug-sample centos8-gdb /bin/bash
# in centos8 container
cd /delve-debug-sample
./delve-debug-sample &
gcore <PID>
exit

# on MacOS
dlv core delve-debug-sample core.<PID>
(dlv) goroutines

profile

curl "localhost:12001/debug/pprof/trace?seconds=5" > app5s.pprof & \
for i in {1..5}; do curl "localhost:12000/foo"; done

go tool trace app5s.pprof

2020/02/15 : trace is not available because of issue: cmd/trace: requires HTML imports, which doesn't work on any major browser anymore · Issue #34374 · golang/go