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moby--moby/daemon/top_unix.go
Kir Kolyshkin a41328d570 ContainerTop: improve error message
If "ps" fails, in many cases it prints a meaningful error message
which a user can benefit from. Let's use it.

While at it, let's use errdefs.System to classify the error,
as well as errors.Wrap.

Before:

> $ docker top $CT <any bad ps options>
> Error response from daemon: Error running ps: exit status 1

After:

> $ docker top $CT auxm
> Error response from daemon: ps: error: thread display conflicts with forest display

or

> $ docker top $CT saur
> Error response from daemon: ps: error: conflicting format options

or, if there's no meaningful error on stderr, same as before:

> $ docker top $CT 1234
> Error response from daemon: ps: exit status 1

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
2018-05-24 18:24:36 -07:00

189 lines
4.7 KiB
Go

//+build !windows
package daemon // import "github.com/docker/docker/daemon"
import (
"bytes"
"context"
"fmt"
"os/exec"
"regexp"
"strconv"
"strings"
"github.com/docker/docker/api/types/container"
"github.com/docker/docker/errdefs"
"github.com/pkg/errors"
)
func validatePSArgs(psArgs string) error {
// NOTE: \\s does not detect unicode whitespaces.
// So we use fieldsASCII instead of strings.Fields in parsePSOutput.
// See https://github.com/docker/docker/pull/24358
// nolint: gosimple
re := regexp.MustCompile("\\s+([^\\s]*)=\\s*(PID[^\\s]*)")
for _, group := range re.FindAllStringSubmatch(psArgs, -1) {
if len(group) >= 3 {
k := group[1]
v := group[2]
if k != "pid" {
return fmt.Errorf("specifying \"%s=%s\" is not allowed", k, v)
}
}
}
return nil
}
// fieldsASCII is similar to strings.Fields but only allows ASCII whitespaces
func fieldsASCII(s string) []string {
fn := func(r rune) bool {
switch r {
case '\t', '\n', '\f', '\r', ' ':
return true
}
return false
}
return strings.FieldsFunc(s, fn)
}
func appendProcess2ProcList(procList *container.ContainerTopOKBody, fields []string) {
// Make sure number of fields equals number of header titles
// merging "overhanging" fields
process := fields[:len(procList.Titles)-1]
process = append(process, strings.Join(fields[len(procList.Titles)-1:], " "))
procList.Processes = append(procList.Processes, process)
}
func hasPid(procs []uint32, pid int) bool {
for _, p := range procs {
if int(p) == pid {
return true
}
}
return false
}
func parsePSOutput(output []byte, procs []uint32) (*container.ContainerTopOKBody, error) {
procList := &container.ContainerTopOKBody{}
lines := strings.Split(string(output), "\n")
procList.Titles = fieldsASCII(lines[0])
pidIndex := -1
for i, name := range procList.Titles {
if name == "PID" {
pidIndex = i
break
}
}
if pidIndex == -1 {
return nil, fmt.Errorf("Couldn't find PID field in ps output")
}
// loop through the output and extract the PID from each line
// fixing #30580, be able to display thread line also when "m" option used
// in "docker top" client command
preContainedPidFlag := false
for _, line := range lines[1:] {
if len(line) == 0 {
continue
}
fields := fieldsASCII(line)
var (
p int
err error
)
if fields[pidIndex] == "-" {
if preContainedPidFlag {
appendProcess2ProcList(procList, fields)
}
continue
}
p, err = strconv.Atoi(fields[pidIndex])
if err != nil {
return nil, fmt.Errorf("Unexpected pid '%s': %s", fields[pidIndex], err)
}
if hasPid(procs, p) {
preContainedPidFlag = true
appendProcess2ProcList(procList, fields)
continue
}
preContainedPidFlag = false
}
return procList, nil
}
// psPidsArg converts a slice of PIDs to a string consisting
// of comma-separated list of PIDs prepended by "-q".
// For example, psPidsArg([]uint32{1,2,3}) returns "-q1,2,3".
func psPidsArg(pids []uint32) string {
b := []byte{'-', 'q'}
for i, p := range pids {
b = strconv.AppendUint(b, uint64(p), 10)
if i < len(pids)-1 {
b = append(b, ',')
}
}
return string(b)
}
// ContainerTop lists the processes running inside of the given
// container by calling ps with the given args, or with the flags
// "-ef" if no args are given. An error is returned if the container
// is not found, or is not running, or if there are any problems
// running ps, or parsing the output.
func (daemon *Daemon) ContainerTop(name string, psArgs string) (*container.ContainerTopOKBody, error) {
if psArgs == "" {
psArgs = "-ef"
}
if err := validatePSArgs(psArgs); err != nil {
return nil, err
}
container, err := daemon.GetContainer(name)
if err != nil {
return nil, err
}
if !container.IsRunning() {
return nil, errNotRunning(container.ID)
}
if container.IsRestarting() {
return nil, errContainerIsRestarting(container.ID)
}
procs, err := daemon.containerd.ListPids(context.Background(), container.ID)
if err != nil {
return nil, err
}
args := strings.Split(psArgs, " ")
pids := psPidsArg(procs)
output, err := exec.Command("ps", append(args, pids)...).Output()
if err != nil {
// some ps options (such as f) can't be used together with q,
// so retry without it
output, err = exec.Command("ps", args...).Output()
if err != nil {
if ee, ok := err.(*exec.ExitError); ok {
// first line of stderr shows why ps failed
line := bytes.SplitN(ee.Stderr, []byte{'\n'}, 2)
if len(line) > 0 && len(line[0]) > 0 {
err = errors.New(string(line[0]))
}
}
return nil, errdefs.System(errors.Wrap(err, "ps"))
}
}
procList, err := parsePSOutput(output, procs)
if err != nil {
return nil, err
}
daemon.LogContainerEvent(container, "top")
return procList, nil
}