Merge pull request opensearch-project#178 from derekparker/cgroup-v2

pkg/discovery: Support cgroupv2

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/alecthomas/kong v0.2.22
 	github.com/aquasecurity/libbpfgo v0.2.2-libbpf-0.5.0
 	github.com/cespare/xxhash/v2 v2.1.2
+	github.com/containerd/cgroups v1.0.2 // indirect
 	github.com/containerd/containerd v1.5.7 // indirect
 	github.com/docker/docker v20.10.11+incompatible
 	github.com/go-kit/log v0.2.0

go.sum

@@ -305,6 +305,8 @@ github.com/containerd/cgroups v0.0.0-20200710171044-318312a37340/go.mod h1:s5q4S
 github.com/containerd/cgroups v0.0.0-20200824123100-0b889c03f102/go.mod h1:s5q4SojHctfxANBDvMeIaIovkq29IP48TKAxnhYRxvo=
 github.com/containerd/cgroups v0.0.0-20210114181951-8a68de567b68/go.mod h1:ZJeTFisyysqgcCdecO57Dj79RfL0LNeGiFUqLYQRYLE=
 github.com/containerd/cgroups v1.0.1/go.mod h1:0SJrPIenamHDcZhEcJMNBB85rHcUsw4f25ZfBiPYRkU=
+github.com/containerd/cgroups v1.0.2 h1:mZBclaSgNDfPWtfhj2xJY28LZ9nYIgzB0pwSURPl6JM=
+github.com/containerd/cgroups v1.0.2/go.mod h1:qpbpJ1jmlqsR9f2IyaLPsdkCdnt0rbDVqIDlhuu5tRY=
 github.com/containerd/console v0.0.0-20180822173158-c12b1e7919c1/go.mod h1:Tj/on1eG8kiEhd0+fhSDzsPAFESxzBBvdyEgyryXffw=
 github.com/containerd/console v0.0.0-20181022165439-0650fd9eeb50/go.mod h1:Tj/on1eG8kiEhd0+fhSDzsPAFESxzBBvdyEgyryXffw=
 github.com/containerd/console v0.0.0-20191206165004-02ecf6a7291e/go.mod h1:8Pf4gM6VEbTNRIT26AyyU7hxdQU3MvAvxVI0sc00XBE=
@@ -388,9 +390,11 @@ github.com/coreos/go-systemd v0.0.0-20161114122254-48702e0da86b/go.mod h1:F5haX7
 github.com/coreos/go-systemd v0.0.0-20180511133405-39ca1b05acc7/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20181012123002-c6f51f82210d/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
+github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf h1:iW4rZ826su+pqaw19uhpSCzhj44qo35pNgKFGqzDKkU=
 github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd/v22 v22.0.0/go.mod h1:xO0FLkIi5MaZafQlIrOotqXZ90ih+1atmu1JpKERPPk=
 github.com/coreos/go-systemd/v22 v22.1.0/go.mod h1:xO0FLkIi5MaZafQlIrOotqXZ90ih+1atmu1JpKERPPk=
+github.com/coreos/go-systemd/v22 v22.3.2 h1:D9/bQk5vlXQFZ6Kwuu6zaiXJ9oTPe68++AzAJc1DzSI=
 github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/coreos/pkg v0.0.0-20160727233714-3ac0863d7acf/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
@@ -714,8 +718,10 @@ github.com/gocql/gocql v0.0.0-20200526081602-cd04bd7f22a7/go.mod h1:DL0ekTmBSTdl
 github.com/godbus/dbus v0.0.0-20151105175453-c7fdd8b5cd55/go.mod h1:/YcGZj5zSblfDWMMoOzV4fas9FZnQYTkDnsGvmh2Grw=
 github.com/godbus/dbus v0.0.0-20180201030542-885f9cc04c9c/go.mod h1:/YcGZj5zSblfDWMMoOzV4fas9FZnQYTkDnsGvmh2Grw=
 github.com/godbus/dbus v0.0.0-20190402143921-271e53dc4968/go.mod h1:/YcGZj5zSblfDWMMoOzV4fas9FZnQYTkDnsGvmh2Grw=
+github.com/godbus/dbus v0.0.0-20190422162347-ade71ed3457e h1:BWhy2j3IXJhjCbC68FptL43tDKIq8FladmaTs3Xs7Z8=
 github.com/godbus/dbus v0.0.0-20190422162347-ade71ed3457e/go.mod h1:bBOAhwG1umN6/6ZUMtDFBMQR8jRg9O75tm9K00oMsK4=
 github.com/godbus/dbus/v5 v5.0.3/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
+github.com/godbus/dbus/v5 v5.0.4 h1:9349emZab16e7zQvpmsbtjc18ykshndd8y2PG3sgJbA=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gofrs/uuid v3.3.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
 github.com/gofrs/uuid v4.0.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=

pkg/discovery/systemd.go

@@ -24,6 +24,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/containerd/cgroups"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/common/model"
@@ -98,6 +99,15 @@ func (c *SystemdDiscoverer) Run(ctx context.Context, up chan<- []*Group) error {
 }
 
 func (c *SystemdDiscoverer) ReconcileUnit(ctx context.Context, unit string) (model.LabelSet, error) {
+	// Note: It's ok to call cgroups.Mode() here instead of storing it somewhere because
+	// internally it's memoized.
+	if cgroups.Mode() == cgroups.Unified {
+		// If we're running under cgroupv2 the perf_event controller is always implicitly enabled
+		// so we don't have to do anything special here.
+		path := fmt.Sprintf("/sys/fs/cgroup/system.slice/%s/", unit)
+		return model.LabelSet{CgroupPathLabelName: model.LabelValue(path)}, nil
+	}
+
 	f, err := os.Open(fmt.Sprintf("/sys/fs/cgroup/systemd/system.slice/%s/cgroup.procs", unit))
 	if os.IsNotExist(err) {
 		c.mtx.Lock()