Add timeout to zfs/zpool commands, except zfs send/receive commands

Fixes #70

utils.go

@@ -2,38 +2,60 @@ package zfs
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/google/uuid"
 )
 
+const (
+	cmdtimeoutEnv = "COMMAND_TIMEOUT"
+)
+
 type command struct {
 	Command string
 	Stdin   io.Reader
 	Stdout  io.Writer
+	timeout *time.Duration
+}
+
+func getCommandTimeout() *time.Duration {
+	value := os.Getenv(cmdtimeoutEnv)
+	if timeout, err := time.ParseDuration(value); value != "" && err == nil {
+		return &timeout
+	}
+	return nil
 }
 
 func (c *command) Run(arg ...string) ([][]string, error) {
 	cmd := exec.Command(c.Command, arg...)
+	if c.timeout != nil {
+		ctx, cancel := context.WithTimeout(context.TODO(), *c.timeout)
+		defer cancel()
+		cmd = exec.CommandContext(ctx, c.Command, arg...)
+	}
 
-	var stdout, stderr bytes.Buffer
+	if c.Stdin != nil {
+		cmd.Stdin = c.Stdin
+	}
 
+	var stdout bytes.Buffer
 	if c.Stdout == nil {
 		cmd.Stdout = &stdout
 	} else {
 		cmd.Stdout = c.Stdout
 	}
 
-	if c.Stdin != nil {
-		cmd.Stdin = c.Stdin
-	}
+	var stderr bytes.Buffer
 	cmd.Stderr = &stderr
 
 	id := uuid.New().String()

zfs.go

@@ -114,7 +114,7 @@ func zfs(arg ...string) error {
 
 // zfs is a helper function to wrap typical calls to zfs.
 func zfsOutput(arg ...string) ([][]string, error) {
-	c := command{Command: "zfs"}
+	c := command{Command: "zfs", timeout: getCommandTimeout()}
 	return c.Run(arg...)
 }
 

zpool.go

@@ -36,7 +36,7 @@ func zpool(arg ...string) error {
 
 // zpool is a helper function to wrap typical calls to zpool.
 func zpoolOutput(arg ...string) ([][]string, error) {
-	c := command{Command: "zpool"}
+	c := command{Command: "zpool", timeout: getCommandTimeout()}
 	return c.Run(arg...)
 }