Add new method to get memory ignoring cgroups

In PR #50, the behavior of GetMem() was changed to return the amount of
memory used / available within the current cgroup. There are some use
cases that you don't want cgroup-constrained memory information. A new
GetMemIgnoringCGroups method has been introduced to provide the system
wide memory information.

[#179517901] Update Bosh Agent to correctly report memory used in `bosh vms --vitals` and related code paths, and publish new stemcells

Signed-off-by: Brian Upton <bupton@vmware.com>

concrete_sigar.go

@@ -56,6 +56,12 @@ func (c *ConcreteSigar) GetMem() (Mem, error) {
 	return m, err
 }
 
+func (c *ConcreteSigar) GetMemIgnoringCGroups() (Mem, error) {
+	m := Mem{}
+	err := m.GetIgnoringCGroups()
+	return m, err
+}
+
 func (c *ConcreteSigar) GetSwap() (Swap, error) {
 	s := Swap{}
 	err := s.Get()

concrete_sigar_test.go

@@ -68,6 +68,9 @@ var _ = Describe("ConcreteSigar", func() {
 
 		Expect(mem.Total).To(BeNumerically(">", 0))
 		Expect(mem.Used + mem.Free).To(BeNumerically("<=", mem.Total))
+
+		mem, err = concreteSigar.GetMemIgnoringCGroups()
+		Expect(err).ToNot(HaveOccurred())
 	})
 
 	It("GetSwap", func() {

sigar_darwin.go

@@ -68,6 +68,10 @@ func (self *Mem) Get() error {
 	return nil
 }
 
+func (self *Mem) GetIgnoringCGroups() error {
+	return self.Get()
+}
+
 type xsw_usage struct {
 	Total, Avail, Used uint64
 }

sigar_linux.go

@@ -100,6 +100,14 @@ func (self *Uptime) Get() error {
 }
 
 func (self *Mem) Get() error {
+	return self.get(false)
+}
+
+func (self *Mem) GetIgnoringCGroups() error {
+	return self.get(true)
+}
+
+func (self *Mem) get(ignoreCGroups bool) error {
 	var available uint64 = MaxUint64
 	var buffers, cached uint64
 	table := map[string]*uint64{
@@ -123,6 +131,10 @@ func (self *Mem) Get() error {
 	self.Used = self.Total - self.Free
 	self.ActualUsed = self.Total - self.ActualFree
 
+	if ignoreCGroups {
+		return nil
+	}
+
 	// Instead of detecting if this code is run within a container
 	// or not (*), we simply attempt to retrieve the cgroup
 	// information about memory limits and usage and if present

sigar_linux_test.go

@@ -883,6 +883,27 @@ DirectMap2M:    34983936 kB`)
 				})
 			})
 
+			Describe("When cgroups are enabled but the GetIgnoringCGroups method is called", func() {
+				// cgroup = '/user'
+				// The other tests use cgroup = '/'. This reduces the amount of changes needed
+				BeforeEach(func() {
+					cgroupSetup(`4:memory:/user`)
+					memInfoWithMemAvailable()
+					memLimitSetup2(`/user`, `21390950400`)
+					memUsageWithSwap(`/user`)
+				})
+
+				It("returns the system memory info", func() {
+					mem := Mem{}
+					err := mem.GetIgnoringCGroups()
+					Expect(err).ToNot(HaveOccurred())
+
+					Expect(mem.Total).To(BeNumerically("==", 35008180*1024))
+					Expect(mem.Free).To(BeNumerically("==", 487816*1024))
+					Expect(mem.ActualFree).To(BeNumerically("==", 20913400*1024))
+					Expect(mem.ActualUsed).To(BeNumerically("==", 14433054720))
+				})
+			})
 		})
 
 		Describe("Swap", func() {

sigar_windows.go

@@ -71,6 +71,10 @@ func (m *Mem) Get() error {
 	return nil
 }
 
+func (m *Mem) GetIgnoringCGroups() error {
+	return m.Get()
+}
+
 func (s *Swap) Get() error {
 	const MB = 1024 * 1024
 	out, err := exec.Command("wmic", "pagefile", "list", "full").Output()