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Add support for creating cgroups in runtime section

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Implements https://github.com/moby/tool/pull/181

Design for things like Kubernetes setup that requires some cgroups to
exist when the service starts but it is not running in these, other
services are, so there would be a race if they are not created in each.

Essentially it is just a sugared `mkdir` in all the cgroup dirs.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>
This commit is contained in:
Justin Cormack
2017-11-17 14:12:41 +00:00
parent 10bae91564
commit 6cb919b489
2 changed files with 30 additions and 7 deletions
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35
pkg/init/cmd/service/prepare.go
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@@ -14,15 +14,11 @@ import (
"golang.org/x/sys/unix"
)
const (
wgPath = "/usr/bin/wg"
nsenterPath = "/usr/bin/nsenter-net"
)
// Note these definitions are from moby/tool/src/moby/config.go and should be kept in sync
// Runtime is the type of config processed at runtime, not used to build the OCI spec
type Runtime struct {
Cgroups []string `yaml:"cgroups" json:"cgroups,omitempty"`
Mounts []specs.Mount `yaml:"mounts" json:"mounts,omitempty"`
Mkdir []string `yaml:"mkdir" json:"mkdir,omitempty"`
Interfaces []Interface `yaml:"interfaces" json:"interfaces,omitempty"`
@@ -122,7 +118,27 @@ func parseMountOptions(options []string) (int, string) {
return flag, strings.Join(data, ",")
}
// prepareFilesystem sets up the mounts, before the container is created
// newCgroup creates a cgroup (ie directory) under all directories in /sys/fs/cgroup
// we could use github.com/containerd/cgroups but it has a lot of deps and this is just a sugary mkdir
func newCgroup(cgroup string) error {
dirs, err := ioutil.ReadDir("/sys/fs/cgroup")
if err != nil {
return err
}
for _, dir := range dirs {
if !dir.IsDir() {
continue
}
if err := os.MkdirAll(filepath.Join("/sys/fs/cgroup", dir.Name(), cgroup), 0755); err != nil {
log.Printf("cgroup error: %v", err)
}
}
return nil
}
// prepareFilesystem sets up the mounts and cgroups, before the container is created
func prepareFilesystem(path string, runtime Runtime) error {
// execute the runtime config that should be done up front
// we execute Mounts before Mkdir so you can make a directory under a mount
@@ -157,6 +173,13 @@ func prepareFilesystem(path string, runtime Runtime) error {
}
}
for _, cgroup := range runtime.Cgroups {
// currently no way to specify resource limits on new cgroups at creation time
if err := newCgroup(cgroup); err != nil {
return fmt.Errorf("Cannot create cgroup %s: %v", cgroup, err)
}
}
return nil
}