Change Load function in order to be more lenient on subsystems' checking

ChrsMark · ChrsMark · commit f6cbfb45aec6 · 2018-11-02T10:38:52.000+02:00
Currently when a cgroup path is not found under a subsystem's directory
Load function will fail completely. This can be blocking when a subsystem
is taking time to update its cgroups. This commit makes Load to by-pass
any not-found subsystem returning a Cgroup with a list of the
only-found subsystems.

Signed-off-by: Chris Mark &lt;chrismarkou92@gmail.com&gt;
diff --git a/cgroup.go b/cgroup.go
@@ -48,11 +48,12 @@ func New(hierarchy Hierarchy, path Path, resources *specs.LinuxResources) (Cgrou
 
 // Load will load an existing cgroup and allow it to be controlled
 func Load(hierarchy Hierarchy, path Path) (Cgroup, error) {
+	var activeSubsystems []Subsystem
 	subsystems, err := hierarchy()
 	if err != nil {
 		return nil, err
 	}
-	// check the the subsystems still exist
+	// check that the subsystems still exist, and keep only those that actually exist
 	for _, s := range pathers(subsystems) {
 		p, err := path(s.Name())
 		if err != nil {
@@ -63,14 +64,15 @@ func Load(hierarchy Hierarchy, path Path) (Cgroup, error) {
 		}
 		if _, err := os.Lstat(s.Path(p)); err != nil {
 			if os.IsNotExist(err) {
-				return nil, ErrCgroupDeleted
+				continue
 			}
 			return nil, err
 		}
+		activeSubsystems = append(activeSubsystems, s)
 	}
 	return &cgroup{
 		path:       path,
-		subsystems: subsystems,
+		subsystems: activeSubsystems,
 	}, nil
 }
 

Original file line number	Diff line number	Diff line change
`@@ -48,11 +48,12 @@ func New(hierarchy Hierarchy, path Path, resources *specs.LinuxResources) (Cgrou`
`48`	`48`
`49`	`49`	`// Load will load an existing cgroup and allow it to be controlled`
`50`	`50`	`func Load(hierarchy Hierarchy, path Path) (Cgroup, error) {`
	`51`	`+ var activeSubsystems []Subsystem`
`51`	`52`	`subsystems, err := hierarchy()`
`52`	`53`	`if err != nil {`
`53`	`54`	`return nil, err`
`54`	`55`	`}`
`55`		`- // check the the subsystems still exist`
	`56`	`+ // check that the subsystems still exist, and keep only those that actually exist`
`56`	`57`	`for _, s := range pathers(subsystems) {`
`57`	`58`	`p, err := path(s.Name())`
`58`	`59`	`if err != nil {`
`@@ -63,14 +64,15 @@ func Load(hierarchy Hierarchy, path Path) (Cgroup, error) {`
`63`	`64`	`}`
`64`	`65`	`if _, err := os.Lstat(s.Path(p)); err != nil {`
`65`	`66`	`if os.IsNotExist(err) {`
`66`		`- return nil, ErrCgroupDeleted`
	`67`	`+ continue`
`67`	`68`	`}`
`68`	`69`	`return nil, err`
`69`	`70`	`}`
	`71`	`+ activeSubsystems = append(activeSubsystems, s)`
`70`	`72`	`}`
`71`	`73`	`return &cgroup{`
`72`	`74`	`path: path,`
`73`		`- subsystems: subsystems,`
	`75`	`+ subsystems: activeSubsystems,`
`74`	`76`	`}, nil`
`75`	`77`	`}`
`76`	`78`