remove duplicate --oom-kill-disable warnings on docker run / docker create

This warning was originally added in [moby@3aa70c1], and moved to be printed
on both `run` and `create` in commit 7c514a31c9.

However, [moby@57f1305] (docker 19.03, API 1.40) moved such warnings to
the daemon side. The patch mentioned this issue:

> This patch will have one side-effect; docker cli's that also perform this check
> client-side will print the warning twice; this can be addressed by disabling
> the cli-side check for newer API versions, but will generate a bit of extra
> noise when using an older CLI.

The CLI does not take this into account currently, and still prints warnings
twice; even in cases where the option is not supported by the daemon, and
discarded:

On a host without OomKillDisable support:

    docker create --oom-kill-disable alpine
    WARNING: Disabling the OOM killer on containers without setting a '-m/--memory' limit may be dangerous.
    WARNING: Your kernel does not support OomKillDisable. OomKillDisable discarded.

On a host that supports it:

    docker create --oom-kill-disable alpine
    WARNING: Disabling the OOM killer on containers without setting a '-m/--memory' limit may be dangerous.
    WARNING: OOM killer is disabled for the container, but no memory limit is set, this can result in the system running out of resources.

This patch removes the client-side warning, leaving it to the daemon to
report if any warnings should produced (and the client to print them).

With this patch applied:

On a host without OomKillDisable support:

    docker create --oom-kill-disable alpine
    WARNING: Your kernel does not support OomKillDisable. OomKillDisable discarded.

On a host that supports it:

    docker create --oom-kill-disable alpine
    WARNING: OOM killer is disabled for the container, but no memory limit is set, this can result in the system running out of resources.

[moby@3aa70c1]: 3aa70c1948
[moby@57f1305]: 57f1305e74

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/container/create.go

@@ -207,7 +207,6 @@ func createContainer(ctx context.Context, dockerCli command.Cli, containerCfg *c
 	hostConfig := containerCfg.HostConfig
 	networkingConfig := containerCfg.NetworkingConfig
 
-	warnOnOomKillDisable(*hostConfig, dockerCli.Err())
 	warnOnLocalhostDNS(*hostConfig, dockerCli.Err())
 
 	var (
@@ -299,12 +298,6 @@ func createContainer(ctx context.Context, dockerCli command.Cli, containerCfg *c
 	return response.ID, err
 }
 
-func warnOnOomKillDisable(hostConfig container.HostConfig, stderr io.Writer) {
-	if hostConfig.OomKillDisable != nil && *hostConfig.OomKillDisable && hostConfig.Memory == 0 {
-		_, _ = fmt.Fprintln(stderr, "WARNING: Disabling the OOM killer on containers without setting a '-m/--memory' limit may be dangerous.")
-	}
-}
-
 // check the DNS settings passed via --dns against localhost regexp to warn if
 // they are trying to set a DNS to a localhost address
 func warnOnLocalhostDNS(hostConfig container.HostConfig, stderr io.Writer) {

cli/command/container/create_test.go

@@ -270,31 +270,24 @@ func TestNewCreateCommandWithContentTrustErrors(t *testing.T) {
 
 func TestNewCreateCommandWithWarnings(t *testing.T) {
 	testCases := []struct {
-		name    string
-		args    []string
-		warning bool
+		name     string
+		args     []string
+		warnings []string
+		warning  bool
 	}{
 		{
-			name: "container-create-without-oom-kill-disable",
+			name: "container-create-no-warnings",
 			args: []string{"image:tag"},
 		},
 		{
-			name: "container-create-oom-kill-disable-false",
-			args: []string{"--oom-kill-disable=false", "image:tag"},
+			name:     "container-create-daemon-single-warning",
+			args:     []string{"image:tag"},
+			warnings: []string{"warning from daemon"},
 		},
 		{
-			name:    "container-create-oom-kill-without-memory-limit",
-			args:    []string{"--oom-kill-disable", "image:tag"},
-			warning: true,
-		},
-		{
-			name:    "container-create-oom-kill-true-without-memory-limit",
-			args:    []string{"--oom-kill-disable=true", "image:tag"},
-			warning: true,
-		},
-		{
-			name: "container-create-oom-kill-true-with-memory-limit",
-			args: []string{"--oom-kill-disable=true", "--memory=100M", "image:tag"},
+			name:     "container-create-daemon-multiple-warnings",
+			args:     []string{"image:tag"},
+			warnings: []string{"warning from daemon", "another warning from daemon"},
 		},
 		{
 			name:    "container-create-localhost-dns",
@@ -316,7 +309,7 @@ func TestNewCreateCommandWithWarnings(t *testing.T) {
 					platform *specs.Platform,
 					containerName string,
 				) (container.CreateResponse, error) {
-					return container.CreateResponse{}, nil
+					return container.CreateResponse{Warnings: tc.warnings}, nil
 				},
 			})
 			cmd := NewCreateCommand(fakeCLI)
@@ -324,7 +317,7 @@ func TestNewCreateCommandWithWarnings(t *testing.T) {
 			cmd.SetArgs(tc.args)
 			err := cmd.Execute()
 			assert.NilError(t, err)
-			if tc.warning {
+			if tc.warning || len(tc.warnings) > 0 {
 				golden.Assert(t, fakeCLI.ErrBuffer().String(), tc.name+".golden")
 			} else {
 				assert.Equal(t, fakeCLI.ErrBuffer().String(), "")

cli/command/container/testdata/container-create-daemon-multiple-warnings.golden

@@ -0,0 +1,2 @@
+WARNING: warning from daemon
+WARNING: another warning from daemon

cli/command/container/testdata/container-create-daemon-single-warning.golden

@@ -0,0 +1 @@
+WARNING: warning from daemon

cli/command/container/testdata/container-create-oom-kill-true-without-memory-limit.golden

@@ -1 +0,0 @@
-WARNING: Disabling the OOM killer on containers without setting a '-m/--memory' limit may be dangerous.

cli/command/container/testdata/container-create-oom-kill-without-memory-limit.golden

@@ -1 +0,0 @@
-WARNING: Disabling the OOM killer on containers without setting a '-m/--memory' limit may be dangerous.