summaryrefslogtreecommitdiff
path: root/libpod/container_top_linux.go
blob: ee03570abbcaaaa69807fd7135930c8ff38ed2aa (plain)
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
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
// +build linux

package libpod

import (
	"bufio"
	"os"
	"strconv"
	"strings"

	"github.com/containers/podman/v3/libpod/define"
	"github.com/containers/podman/v3/pkg/rootless"
	"github.com/containers/psgo"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// Top gathers statistics about the running processes in a container. It returns a
// []string for output
func (c *Container) Top(descriptors []string) ([]string, error) {
	if c.config.NoCgroups {
		return nil, errors.Wrapf(define.ErrNoCgroups, "cannot run top on container %s as it did not create a cgroup", c.ID())
	}

	conStat, err := c.State()
	if err != nil {
		return nil, errors.Wrapf(err, "unable to look up state for %s", c.ID())
	}
	if conStat != define.ContainerStateRunning {
		return nil, errors.Errorf("top can only be used on running containers")
	}

	// Also support comma-separated input.
	psgoDescriptors := []string{}
	for _, d := range descriptors {
		for _, s := range strings.Split(d, ",") {
			if s != "" {
				psgoDescriptors = append(psgoDescriptors, s)
			}
		}
	}

	// If we encountered an ErrUnknownDescriptor error, fallback to executing
	// ps(1). This ensures backwards compatibility to users depending on ps(1)
	// and makes sure we're ~compatible with docker.
	output, psgoErr := c.GetContainerPidInformation(psgoDescriptors)
	if psgoErr == nil {
		return output, nil
	}
	if errors.Cause(psgoErr) != psgo.ErrUnknownDescriptor {
		return nil, psgoErr
	}

	output, err = c.execPS(descriptors)
	if err != nil {
		return nil, errors.Wrapf(err, "error executing ps(1) in the container")
	}

	// Trick: filter the ps command from the output instead of
	// checking/requiring PIDs in the output.
	filtered := []string{}
	cmd := strings.Join(descriptors, " ")
	for _, line := range output {
		if !strings.Contains(line, cmd) {
			filtered = append(filtered, line)
		}
	}

	return filtered, nil
}

// GetContainerPidInformation returns process-related data of all processes in
// the container.  The output data can be controlled via the `descriptors`
// argument which expects format descriptors and supports all AIXformat
// descriptors of ps (1) plus some additional ones to for instance inspect the
// set of effective capabilities.  Each element in the returned string slice
// is a tab-separated string.
//
// For more details, please refer to github.com/containers/psgo.
func (c *Container) GetContainerPidInformation(descriptors []string) ([]string, error) {
	pid := strconv.Itoa(c.state.PID)
	// TODO: psgo returns a [][]string to give users the ability to apply
	//       filters on the data.  We need to change the API here
	//       to return a [][]string if we want to make use of
	//       filtering.
	opts := psgo.JoinNamespaceOpts{FillMappings: rootless.IsRootless()}

	psgoOutput, err := psgo.JoinNamespaceAndProcessInfoWithOptions(pid, descriptors, &opts)
	if err != nil {
		return nil, err
	}
	res := []string{}
	for _, out := range psgoOutput {
		res = append(res, strings.Join(out, "\t"))
	}
	return res, nil
}

// execPS executes ps(1) with the specified args in the container.
func (c *Container) execPS(args []string) ([]string, error) {
	rPipe, wPipe, err := os.Pipe()
	if err != nil {
		return nil, err
	}
	defer wPipe.Close()
	defer rPipe.Close()

	rErrPipe, wErrPipe, err := os.Pipe()
	if err != nil {
		return nil, err
	}
	defer wErrPipe.Close()
	defer rErrPipe.Close()

	streams := new(define.AttachStreams)
	streams.OutputStream = wPipe
	streams.ErrorStream = wErrPipe
	streams.AttachOutput = true
	streams.AttachError = true

	stdout := []string{}
	go func() {
		scanner := bufio.NewScanner(rPipe)
		for scanner.Scan() {
			stdout = append(stdout, scanner.Text())
		}
	}()
	stderr := []string{}
	go func() {
		scanner := bufio.NewScanner(rErrPipe)
		for scanner.Scan() {
			stderr = append(stderr, scanner.Text())
		}
	}()

	cmd := append([]string{"ps"}, args...)
	config := new(ExecConfig)
	config.Command = cmd
	ec, err := c.Exec(config, streams, nil)
	if err != nil {
		return nil, err
	} else if ec != 0 {
		return nil, errors.Errorf("Runtime failed with exit status: %d and output: %s", ec, strings.Join(stderr, " "))
	}

	if logrus.GetLevel() >= logrus.DebugLevel {
		// If we're running in debug mode or higher, we might want to have a
		// look at stderr which includes debug logs from conmon.
		for _, log := range stderr {
			logrus.Debugf("%s", log)
		}
	}

	return stdout, nil
}