prometheus/cadvisor
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Lazily init DBus only when it is needed

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OpenShift has some cAdvisor packages in its import chain. The init() here
invokes Dbus start even when cAdvisor is not actively running or being
used (in our packages).  This change makes the systemd check and dbus
initialization and connection lazy, occuring only the first time someone
invokes UseSystemd().
This commit is contained in:
Clayton Coleman 2015-03-19 16:33:51 -04:00
parent 19c6e473b2
commit 9ce178f707
1 changed files with 19 additions and 18 deletions
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37
container/docker/factory.go
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@ -21,6 +21,7 @@ import (
"regexp"
"strconv"
"strings"
"sync"
"github.com/docker/libcontainer/cgroups"
"github.com/docker/libcontainer/cgroups/systemd"
@ -43,23 +44,23 @@ var dockerRootDir = flag.String("docker_root", "/var/lib/docker", "Absolute path
// Whether the system is using Systemd.
var useSystemd bool
func init() {
useSystemd = systemd.UseSystemd()
if !useSystemd {
// Second attempt at checking for systemd, check for a "name=systemd" cgroup.
mnt, err := cgroups.FindCgroupMountpoint("cpu")
if err == nil {
// systemd presence does not mean systemd controls cgroups.
// If system.slice cgroup exists, then systemd is taking control.
// This breaks if user creates system.slice manually :)
useSystemd = utils.FileExists(mnt + "/system.slice")
}
}
}
var check = sync.Once{}
func UseSystemd() bool {
// init would run and initialize useSystemd before we can call this method.
check.Do(func() {
// run and initialize useSystemd
useSystemd = systemd.UseSystemd()
if !useSystemd {
// Second attempt at checking for systemd, check for a "name=systemd" cgroup.
mnt, err := cgroups.FindCgroupMountpoint("cpu")
if err == nil {
// systemd presence does not mean systemd controls cgroups.
// If system.slice cgroup exists, then systemd is taking control.
// This breaks if user creates system.slice manually :)
useSystemd = utils.FileExists(mnt + "/system.slice")
}
}
})
return useSystemd
}
@ -108,7 +109,7 @@ func ContainerNameToDockerId(name string) string {
id := path.Base(name)
// Turn systemd cgroup name into Docker ID.
if useSystemd {
if UseSystemd() {
id = strings.TrimPrefix(id, "docker-")
id = strings.TrimSuffix(id, ".scope")
}
@ -119,7 +120,7 @@ func ContainerNameToDockerId(name string) string {
// Returns a full container name for the specified Docker ID.
func FullContainerName(dockerId string) string {
// Add the full container name.
if useSystemd {
if UseSystemd() {
return path.Join("/system.slice", fmt.Sprintf("docker-%s.scope", dockerId))
} else {
return path.Join("/docker", dockerId)
@ -207,7 +208,7 @@ func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo) error {
}
}
if useSystemd {
if UseSystemd() {
glog.Infof("System is using systemd")
}