pkg: new package cgroups

provide a package for managing cgroups.  This is not supposed to be a
complete implementation with all the features supported by cgroups,
but it is a minimal implementation designed around what libpod needs
and it is currently using.

For example, it is currently possible to Apply only the pids limit,
as it is used by libpod for stopping containers, any other Apply will
just fail.

The main goal here is to have a minimal library where we have full
control, so we can start playing with cgroup v2.

When the need arises, we can add more features.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

1 files changed, 92 insertions, 0 deletions

diff --git a/pkg/cgroups/systemd.go b/pkg/cgroups/systemd.go
new file mode 100644
index 000000000..e72e456bc
--- /dev/null
+++ b/pkg/cgroups/systemd.go
@@ -0,0 +1,92 @@
+package cgroups
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	systemdDbus "github.com/coreos/go-systemd/dbus"
+	"github.com/godbus/dbus"
+)
+
+func systemdCreate(path string) error {
+	c, err := systemdDbus.New()
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+
+	slice, name := filepath.Split(path)
+	slice = strings.TrimSuffix(slice, "/")
+
+	var lastError error
+	for i := 0; i < 2; i++ {
+		properties := []systemdDbus.Property{
+			systemdDbus.PropDescription(fmt.Sprintf("cgroup %s", name)),
+			systemdDbus.PropWants(slice),
+		}
+		pMap := map[string]bool{
+			"DefaultDependencies": false,
+			"MemoryAccounting":    true,
+			"CPUAccounting":       true,
+			"BlockIOAccounting":   true,
+		}
+		if i == 0 {
+			pMap["Delegate"] = true
+		}
+		for k, v := range pMap {
+			p := systemdDbus.Property{
+				Name:  k,
+				Value: dbus.MakeVariant(v),
+			}
+			properties = append(properties, p)
+		}
+
+		ch := make(chan string)
+		_, err = c.StartTransientUnit(name, "replace", properties, ch)
+		if err != nil {
+			lastError = err
+			continue
+		}
+		<-ch
+		return nil
+	}
+	return lastError
+}
+
+/*
+   systemdDestroy is copied from containerd/cgroups/systemd.go file, that
+   has the following license:
+
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+func systemdDestroy(path string) error {
+	c, err := systemdDbus.New()
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+
+	name := filepath.Base(path)
+
+	ch := make(chan string)
+	_, err = c.StopUnit(name, "replace", ch)
+	if err != nil {
+		return err
+	}
+	<-ch
+	return nil
+}