packer-cn/panic.go

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package main
import (
"fmt"
"io"
"os"
"strings"
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"github.com/mitchellh/panicwrap"
)
// This is output if a panic happens.
const panicOutput = `
!!!!!!!!!!!!!!!!!!!!!!!!!!! PACKER CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!
Packer crashed! This is always indicative of a bug within Packer.
A crash log has been placed at "crash.log" relative to your current
working directory. It would be immensely helpful if you could please
report the crash with Packer[1] so that we can fix this.
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[1]: https://github.com/mitchellh/packer/issues
!!!!!!!!!!!!!!!!!!!!!!!!!!! PACKER CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!
`
// panicHandler is what is called by panicwrap when a panic is encountered
// within Packer. It is guaranteed to run after the resulting process has
// exited so we can take the log file, add in the panic, and store it
// somewhere locally.
func panicHandler(logF *os.File) panicwrap.HandlerFunc {
return func(m string) {
// Write away just output this thing on stderr so that it gets
// shown in case anything below fails.
fmt.Fprintf(os.Stderr, fmt.Sprintf("%s\n", m))
// Create the crash log file where we'll write the logs
f, err := os.Create("crash.log")
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to create crash log file: %s", err)
return
}
defer f.Close()
// Seek the log file back to the beginning
if _, err = logF.Seek(0, 0); err != nil {
fmt.Fprintf(os.Stderr, "Failed to seek log file for crash: %s", err)
return
}
// Copy the contents to the crash file. This will include
// the panic that just happened.
if _, err = io.Copy(f, logF); err != nil {
fmt.Fprintf(os.Stderr, "Failed to write crash log: %s", err)
return
}
// Tell the user a crash occurred in some helpful way that
// they'll hopefully notice.
fmt.Printf("\n\n")
fmt.Println(strings.TrimSpace(panicOutput))
}
}