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samuelkarpsamuelkarp
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ctr: make kill use stop-signal by default
The OCI image specification includes a `StopSignal` field in the image configuration, denoting the system call signal to be sent to the container to exit. This commit adds a new `WithImageStopSignal` container option that can be used for storing the `StopSignal` field as a label on the container. This commit also adjusts `ctr run` to call `WithImageStopSignal` and `ctr tasks kill` to send the signal stored in that label by default. Signed-off-by: Samuel Karp <[email protected]>
1 parent b392a3a commit 607888c

4 files changed

Lines changed: 97 additions & 5 deletions

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‎cmd/ctr/commands/run/run_unix.go‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -27,7 +27,7 @@ import (
2727
"github.com/containerd/containerd/cmd/ctr/commands"
2828
"github.com/containerd/containerd/contrib/nvidia"
2929
"github.com/containerd/containerd/oci"
30-
specs "github.com/opencontainers/runtime-spec/specs-go"
30+
"github.com/opencontainers/runtime-spec/specs-go"
3131
"github.com/pkg/errors"
3232
"github.com/urfave/cli"
3333
)
@@ -58,6 +58,7 @@ func NewContainer(ctx gocontext.Context, client *containerd.Client, context *cli
5858
spec containerd.NewContainerOpts
5959
)
6060

61+
cOpts = append(cOpts, containerd.WithContainerLabels(commands.LabelArgs(context.StringSlice("label"))))
6162
if config {
6263
opts = append(opts, oci.WithSpecFromFile(context.String("config")))
6364
} else {
@@ -98,7 +99,8 @@ func NewContainer(ctx gocontext.Context, client *containerd.Client, context *cli
9899
// Even when "readonly" is set, we don't use KindView snapshot here. (#1495)
99100
// We pass writable snapshot to the OCI runtime, and the runtime remounts it as read-only,
100101
// after creating some mount points on demand.
101-
containerd.WithNewSnapshot(id, image))
102+
containerd.WithNewSnapshot(id, image),
103+
containerd.WithImageStopSignal(image, "SIGTERM"))
102104
}
103105
if context.Bool("readonly") {
104106
opts = append(opts, oci.WithRootFSReadonly())
@@ -141,7 +143,6 @@ func NewContainer(ctx gocontext.Context, client *containerd.Client, context *cli
141143
}
142144
}
143145

144-
cOpts = append(cOpts, containerd.WithContainerLabels(commands.LabelArgs(context.StringSlice("label"))))
145146
cOpts = append(cOpts, containerd.WithRuntime(context.String("runtime"), nil))
146147

147148
var s specs.Spec

‎cmd/ctr/commands/tasks/kill.go‎

Lines changed: 15 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -23,14 +23,16 @@ import (
2323
"github.com/urfave/cli"
2424
)
2525

26+
const defaultSignal = "SIGTERM"
27+
2628
var killCommand = cli.Command{
2729
Name: "kill",
2830
Usage: "signal a container (default: SIGTERM)",
2931
ArgsUsage: "[flags] CONTAINER",
3032
Flags: []cli.Flag{
3133
cli.StringFlag{
3234
Name: "signal, s",
33-
Value: "SIGTERM",
35+
Value: "",
3436
Usage: "signal to send to the container",
3537
},
3638
cli.StringFlag{
@@ -47,7 +49,7 @@ var killCommand = cli.Command{
4749
if id == "" {
4850
return errors.New("container id must be provided")
4951
}
50-
signal, err := containerd.ParseSignal(context.String("signal"))
52+
signal, err := containerd.ParseSignal(defaultSignal)
5153
if err != nil {
5254
return err
5355
}
@@ -74,6 +76,17 @@ var killCommand = cli.Command{
7476
if err != nil {
7577
return err
7678
}
79+
if context.String("signal") != "" {
80+
signal, err = containerd.ParseSignal(context.String("signal"))
81+
if err != nil {
82+
return err
83+
}
84+
} else {
85+
signal, err = containerd.GetStopSignal(ctx, container, signal)
86+
if err != nil {
87+
return err
88+
}
89+
}
7790
task, err := container.Task(ctx, nil)
7891
if err != nil {
7992
return err

‎container_opts.go‎

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -76,6 +76,23 @@ func WithContainerLabels(labels map[string]string) NewContainerOpts {
7676
}
7777
}
7878

79+
// WithImageStopSignal sets a well-known containerd label (StopSignalLabel)
80+
// on the container for storing the stop signal specified in the OCI image
81+
// config
82+
func WithImageStopSignal(image Image, defaultSignal string) NewContainerOpts {
83+
return func(ctx context.Context, _ *Client, c *containers.Container) error {
84+
if c.Labels == nil {
85+
c.Labels = make(map[string]string)
86+
}
87+
stopSignal, err := GetOCIStopSignal(ctx, image, defaultSignal)
88+
if err != nil {
89+
return err
90+
}
91+
c.Labels[StopSignalLabel] = stopSignal
92+
return nil
93+
}
94+
}
95+
7996
// WithSnapshotter sets the provided snapshotter for use by the container
8097
//
8198
// This option must appear before other snapshotter options to have an effect.

‎signals.go‎

Lines changed: 61 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -17,12 +17,73 @@
1717
package containerd
1818

1919
import (
20+
"context"
21+
"encoding/json"
2022
"fmt"
2123
"strconv"
2224
"strings"
2325
"syscall"
26+
27+
"github.com/containerd/containerd/content"
28+
"github.com/containerd/containerd/images"
29+
"github.com/opencontainers/image-spec/specs-go/v1"
2430
)
2531

32+
// StopSignalLabel is a well-known containerd label for storing the stop
33+
// signal specified in the OCI image config
34+
const StopSignalLabel = "io.containerd.image.config.stop-signal"
35+
36+
// GetStopSignal retrieves the container stop signal, specified by the
37+
// well-known containerd label (StopSignalLabel)
38+
func GetStopSignal(ctx context.Context, container Container, defaultSignal syscall.Signal) (syscall.Signal, error) {
39+
labels, err := container.Labels(ctx)
40+
if err != nil {
41+
return -1, err
42+
}
43+
44+
if stopSignal, ok := labels[StopSignalLabel]; ok {
45+
return ParseSignal(stopSignal)
46+
}
47+
48+
return defaultSignal, nil
49+
}
50+
51+
// GetOCIStopSignal retrieves the stop signal specified in the OCI image config
52+
func GetOCIStopSignal(ctx context.Context, image Image, defaultSignal string) (string, error) {
53+
_, err := ParseSignal(defaultSignal)
54+
if err != nil {
55+
return "", err
56+
}
57+
ic, err := image.Config(ctx)
58+
if err != nil {
59+
return "", err
60+
}
61+
var (
62+
ociimage v1.Image
63+
config v1.ImageConfig
64+
)
65+
switch ic.MediaType {
66+
case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
67+
p, err := content.ReadBlob(ctx, image.ContentStore(), ic)
68+
if err != nil {
69+
return "", err
70+
}
71+
72+
if err := json.Unmarshal(p, &ociimage); err != nil {
73+
return "", err
74+
}
75+
config = ociimage.Config
76+
default:
77+
return "", fmt.Errorf("unknown image config media type %s", ic.MediaType)
78+
}
79+
80+
if config.StopSignal == "" {
81+
return defaultSignal, nil
82+
}
83+
84+
return config.StopSignal, nil
85+
}
86+
2687
// ParseSignal parses a given string into a syscall.Signal
2788
// it checks that the signal exists in the platform-appropriate signalMap
2889
func ParseSignal(rawSignal string) (syscall.Signal, error) {

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