Setup panicwrap

log.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"io"
+	"os"
+)
+
+// These are the environmental variables that determine if we log, and if
+// we log whether or not the log should go to a file.
+const EnvLog = "TF_LOG"
+const EnvLogFile = "TF_LOG_PATH"
+
+// logOutput determines where we should send logs (if anywhere).
+func logOutput() (logOutput io.Writer, err error) {
+	logOutput = nil
+	if os.Getenv(EnvLog) != "" {
+		logOutput = os.Stderr
+
+		if logPath := os.Getenv(EnvLogFile); logPath != "" {
+			var err error
+			logOutput, err = os.Create(logPath)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return
+}

main.go

@@ -6,7 +6,9 @@ import (
 	"log"
 	"os"
 
+	"github.com/ActiveState/tail"
 	"github.com/mitchellh/cli"
+	"github.com/mitchellh/panicwrap"
 )
 
 func main() {
@@ -14,7 +16,79 @@ func main() {
 }
 
 func realMain() int {
-	log.SetOutput(ioutil.Discard)
+	var wrapConfig panicwrap.WrapConfig
+
+	if !panicwrap.Wrapped(&wrapConfig) {
+		// Determine where logs should go in general (requested by the user)
+		logWriter, err := logOutput()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Couldn't setup log output: %s", err)
+			return 1
+		}
+
+		// We always send logs to a temporary file that we use in case
+		// there is a panic. Otherwise, we delete it.
+		logTempFile, err := ioutil.TempFile("", "terraform-log")
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Couldn't setup logging tempfile: %s", err)
+			return 1
+		}
+		logTempFile.Close()
+		defer os.Remove(logTempFile.Name())
+
+		// Tell the logger to log to this file
+		os.Setenv(EnvLog, "1")
+		os.Setenv(EnvLogFile, logTempFile.Name())
+
+		if logWriter != nil {
+			// Start tailing the file beforehand to get the data
+			t, err := tail.TailFile(logTempFile.Name(), tail.Config{
+				Follow:    true,
+				Logger:    tail.DiscardingLogger,
+				MustExist: true,
+			})
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Couldn't setup logging tempfile: %s", err)
+				return 1
+			}
+			go func() {
+				for line := range t.Lines {
+					logWriter.Write([]byte(line.Text + "\n"))
+				}
+			}()
+		}
+
+		// Create the configuration for panicwrap and wrap our executable
+		wrapConfig.Handler = panicHandler(logTempFile)
+		exitStatus, err := panicwrap.Wrap(&wrapConfig)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Couldn't start Terraform: %s", err)
+			return 1
+		}
+
+		// If >= 0, we're the parent, so just exit
+		if exitStatus >= 0 {
+			return exitStatus
+		}
+
+		// We're the child, so just close the tempfile we made in order to
+		// save file handles since the tempfile is only used by the parent.
+		logTempFile.Close()
+	}
+
+	// Call the real main
+	return wrappedMain()
+}
+
+func wrappedMain() int {
+	logOutput, err := logOutput()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error starting Terraform: %s", err)
+		return 1
+	}
+	if logOutput != nil {
+		log.SetOutput(logOutput)
+	}
 
 	// Get the command line args. We shortcut "--version" and "-v" to
 	// just show the version.

panic.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/mitchellh/panicwrap"
+)
+
+// This output is shown if a panic happens.
+const panicOutput = `
+
+!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+Terraform crashed! This is always indicative of a bug within Terraform.
+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 Terraform[1] so that we can fix this.
+
+[1]: https://github.com/hashicorp/terraform/issues
+
+!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!
+`
+
+// panicHandler is what is called by panicwrap when a panic is encountered
+// within Terraform. 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) {
+		// Right 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))
+	}
+}