File size: 2,971 Bytes
e36aeda | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 | // Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package debug_test
import (
"io"
"log"
"os"
"os/exec"
"runtime/debug"
)
// ExampleSetCrashOutput_monitor shows an example of using
// [debug.SetCrashOutput] to direct crashes to a "monitor" process,
// for automated crash reporting. The monitor is the same executable,
// invoked in a special mode indicated by an environment variable.
func ExampleSetCrashOutput_monitor() {
appmain()
// This Example doesn't actually run as a test because its
// purpose is to crash, so it has no "Output:" comment
// within the function body.
//
// To observe the monitor in action, replace the entire text
// of this comment with "Output:" and run this command:
//
// $ go test -run=ExampleSetCrashOutput_monitor runtime/debug
// panic: oops
// ...stack...
// monitor: saved crash report at /tmp/10804884239807998216.crash
}
// appmain represents the 'main' function of your application.
func appmain() {
monitor()
// Run the application.
println("hello")
panic("oops")
}
// monitor starts the monitor process, which performs automated
// crash reporting. Call this function immediately within main.
//
// This function re-executes the same executable as a child process,
// in a special mode. In that mode, the call to monitor will never
// return.
func monitor() {
const monitorVar = "RUNTIME_DEBUG_MONITOR"
if os.Getenv(monitorVar) != "" {
// This is the monitor (child) process.
log.SetFlags(0)
log.SetPrefix("monitor: ")
crash, err := io.ReadAll(os.Stdin)
if err != nil {
log.Fatalf("failed to read from input pipe: %v", err)
}
if len(crash) == 0 {
// Parent process terminated without reporting a crash.
os.Exit(0)
}
// Save the crash report securely in the file system.
f, err := os.CreateTemp("", "*.crash")
if err != nil {
log.Fatal(err)
}
if _, err := f.Write(crash); err != nil {
log.Fatal(err)
}
if err := f.Close(); err != nil {
log.Fatal(err)
}
log.Fatalf("saved crash report at %s", f.Name())
}
// This is the application process.
// Fork+exec the same executable in monitor mode.
exe, err := os.Executable()
if err != nil {
log.Fatal(err)
}
cmd := exec.Command(exe, "-test.run=^ExampleSetCrashOutput_monitor$")
// Be selective in which variables we allow the child to inherit.
// Depending on the application, some may be necessary,
// while others (e.g. GOGC, GOMEMLIMIT) may be harmful; see #73490.
cmd.Env = []string{monitorVar + "=1"}
cmd.Stderr = os.Stderr
cmd.Stdout = os.Stderr
pipe, err := cmd.StdinPipe()
if err != nil {
log.Fatalf("StdinPipe: %v", err)
}
debug.SetCrashOutput(pipe.(*os.File), debug.CrashOptions{}) // (this conversion is safe)
if err := cmd.Start(); err != nil {
log.Fatalf("can't start monitor: %v", err)
}
// Now return and start the application proper...
}
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