send in-inode when container-id cannot be retrieved

statsd/container.go

@@ -12,8 +12,9 @@ var (
 )
 
 // getContainerID returns the container ID configured at the client creation
-// It can either be auto-discovered with origin detection or provided by the user.
-// User-defined container ID is prioritized.
+// It can be provided by the user or read from cgroups. If the container ID
+// is not available, it returns the cgroup inode prefixed by "in-" if available.
+// If the cgroup inode is not available, it returns an empty string.
 func getContainerID() string {
 	return containerID
 }

statsd/container_linux.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path"
 	"regexp"
 	"strings"
 	"syscall"
@@ -17,6 +18,9 @@ const (
 	// cgroupPath is the path to the cgroup file where we can find the container id if one exists.
 	cgroupPath = "/proc/self/cgroup"
 
+	// cgroupRootPath is the default path to the cgroup root path
+	cgroupRootPath = "/sys/fs/cgroup"
+
 	// selfMountinfo is the path to the mountinfo path where we can find the container id in case cgroup namespace is preventing the use of /proc/self/cgroup
 	selfMountInfoPath = "/proc/self/mountinfo"
 
@@ -48,29 +52,62 @@ var (
 )
 
 // parseContainerID finds the first container ID reading from r and returns it.
-func parseContainerID(r io.Reader) string {
-	scn := bufio.NewScanner(r)
-	for scn.Scan() {
-		path := expLine.FindStringSubmatch(scn.Text())
-		if len(path) != 2 {
-			// invalid entry, continue
-			continue
-		}
-		if parts := expContainerID.FindStringSubmatch(path[1]); len(parts) == 2 {
-			return parts[1]
-		}
+func parseContainerID(line string) string {
+	path := expLine.FindStringSubmatch(line)
+	if len(path) != 2 {
+		// invalid entry, continue
+		return ""
+	}
+	if parts := expContainerID.FindStringSubmatch(path[1]); len(parts) == 2 {
+		return parts[1]
 	}
 	return ""
 }
 
-// readContainerID attempts to return the container ID from the provided file path or empty on failure.
-func readContainerID(fpath string) string {
+// parseCgroupNodePath parses the cgroup root path from a line formatted as
+// 0::<path> where <path> is the cgroup node prefixed by /sys/fs/cgroup
+func parseCgroupNodePath(line string) string {
+	if strings.HasPrefix(line, "0::") {
+		// return root cgroup
+		return line[3:]
+	}
+	return ""
+}
+
+// readContainerIDOrCgroupInode attempts to return the container ID from the provided file path
+// or the cgroup inode if the container ID is not available. Otherwise, it returns an empty string.
+func readContainerIDOrCgroupInode(cgroupPrefix, fpath string) string {
 	f, err := os.Open(fpath)
 	if err != nil {
 		return ""
 	}
 	defer f.Close()
-	return parseContainerID(f)
+
+	cgroupNodePath := ""
+
+	scn := bufio.NewScanner(f)
+	for scn.Scan() {
+		line := scn.Text()
+		// Return the container id if found
+		if containerID := parseContainerID(line); containerID != "" {
+			return containerID
+		}
+		cgroupNodePath = parseCgroupNodePath(line)
+	}
+
+	// Assumes the file is not a symlink
+	fi, err := os.Stat(path.Clean(cgroupPrefix + cgroupNodePath))
+	if err != nil {
+		return ""
+	}
+	inode := fi.Sys().(*syscall.Stat_t).Ino
+	// Inode 0 indicates that there is no inode.
+	// Inode 1 indicates a bad block
+	// Inode 2 indicates starting of fs nodes
+	if inode > 2 {
+		return fmt.Sprintf("in-%d", inode)
+	}
+	return ""
 }
 
 // Parsing /proc/self/mountinfo is not always reliable in Kubernetes+containerd (at least)
@@ -138,21 +175,23 @@ func isHostCgroupNamespace() bool {
 	return inode == hostCgroupNamespaceInode
 }
 
-// initContainerID initializes the container ID.
-// It can either be provided by the user or read from cgroups.
-func initContainerID(userProvidedID string, cgroupFallback bool) {
+// initContainerIDOrCgroupInode initializes the container ID or the cgroup inode.
+// The container ID can either be provided by the user or read from cgroups.
+// The cgroup inode can only be auto discovered.
+func initContainerIDOrCgroupInode(userProvidedID string, cgroupFallback bool) {
 	initOnce.Do(func() {
 		if userProvidedID != "" {
 			containerID = userProvidedID
 			return
 		}
 
 		if cgroupFallback {
-			if isCgroupV1(mountsPath) || isHostCgroupNamespace() {
-				containerID = readContainerID(cgroupPath)
-			} else {
+			if !(isCgroupV1(mountsPath) || isHostCgroupNamespace()) {
 				containerID = readMountinfo(selfMountInfoPath)
 			}
+			if containerID == "" {
+				containerID = readContainerIDOrCgroupInode(cgroupRootPath, cgroupPath)
+			}
 		}
 	})
 }

statsd/container_stub.go

@@ -3,7 +3,7 @@
 
 package statsd
 
-func initContainerID(userProvidedID string, cgroupFallback bool) {
+func initContainerIDOrCgroupInode(userProvidedID string, cgroupFallback bool) {
 	initOnce.Do(func() {
 		if userProvidedID != "" {
 			containerID = userProvidedID

statsd/container_test.go

@@ -8,40 +8,88 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"strings"
+	"syscall"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
 func TestParseContainerID(t *testing.T) {
 	for input, expectedResult := range map[string]string{
-		`other_line
-10:hugetlb:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-9:cpuset:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-8:pids:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-7:freezer:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-6:cpu,cpuacct:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-5:perf_event:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-4:blkio:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-3:devices:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa
-2:net_cls,net_prio:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa`: "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
-		"10:hugetlb:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa": "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"10:hugetlb:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":         "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"9:cpuset:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":           "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"8:pids:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":             "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"7:freezer:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":          "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"6:cpu,cpuacct:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":      "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"5:perf_event:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":       "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"4:blkio:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":            "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"3:devices:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa":          "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
+		"2:net_cls,net_prio:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa": "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa",
 		"10:hugetlb:/kubepods": "",
 		"11:hugetlb:/ecs/55091c13-b8cf-4801-b527-f4601742204d/432624d2150b349fe35ba397284dea788c2bf66b885d14dfc1569b01890ca7da": "432624d2150b349fe35ba397284dea788c2bf66b885d14dfc1569b01890ca7da",
 		"1:name=systemd:/docker/34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376":                               "34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376",
 		"1:name=systemd:/uuid/34dc0b5e-626f-2c5c-4c51-70e34b10e765":                                                             "34dc0b5e-626f-2c5c-4c51-70e34b10e765",
 		"1:name=systemd:/ecs/34dc0b5e626f2c5c4c5170e34b10e765-1234567890":                                                       "34dc0b5e626f2c5c4c5170e34b10e765-1234567890",
 		"1:name=systemd:/docker/34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376.scope":                         "34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376",
-		`1:name=systemd:/nope
-2:pids:/docker/34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376
-3:cpu:/invalid`: "34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376",
+		"2:pids:/docker/34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376":                                       "34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376",
 	} {
-		id := parseContainerID(strings.NewReader(input))
+		id := parseContainerID(input)
 		assert.Equal(t, expectedResult, id)
 	}
 }
 
+// In order to test with the actual /sys/fs/cgroup file, an integration test running in a container is necessary.
+// When ran on host, /sys/fs/cgroup's inode is 2.
+func TestDefaultCase(t *testing.T) {
+	// Create a dummy cgroup node
+	dummyCgroupNode, err := ioutil.TempDir(os.TempDir(), "sysfscgroup-") // ex: 0::/tmp/sysfscgroup-4222027333/
+	assert.NoError(t, err)
+	defer os.Remove(dummyCgroupNode)
+
+	// Create the file corresponding to /proc/self/cgroup redirecting to the cgroup node
+	tmpFile, err := ioutil.TempFile(os.TempDir(), "procselfcgroup-")
+	assert.NoError(t, err)
+	defer os.Remove(tmpFile.Name())
+
+	// Write the path to the cgroup node in the tmp file
+	procFileContent := `other_line
+0::` + dummyCgroupNode
+	_, err = io.WriteString(tmpFile, procFileContent)
+	assert.NoError(t, err)
+	err = tmpFile.Close()
+	assert.NoError(t, err)
+
+	// Verify that readContainerIDOrCgroupInode returns the inode of dummyCgroupNode
+	inode := readContainerIDOrCgroupInode("", tmpFile.Name())
+
+	fi, err := os.Stat(path.Clean(dummyCgroupNode))
+	assert.NoError(t, err)
+	expectedInode := fi.Sys().(*syscall.Stat_t).Ino
+	assert.Equal(t, fmt.Sprintf("in-%d", expectedInode), inode)
+}
+
+func TestContainerIDIsReturned(t *testing.T) {
+	// Create the file corresponding to /proc/self/cgroup redirecting to the cgroup node
+	tmpFile, err := ioutil.TempFile(os.TempDir(), "fake-cgroup-")
+	assert.NoError(t, err)
+	defer os.Remove(tmpFile.Name())
+
+	// Write the path to the cgroup node in the tmp file
+	procFileContent := `other_line
+0::/
+10:hugetlb:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa`
+	_, err = io.WriteString(tmpFile, procFileContent)
+	assert.NoError(t, err)
+	err = tmpFile.Close()
+	assert.NoError(t, err)
+
+	// Verify that readContainerIDOrCgroupInode returns the cid
+	cid := readContainerIDOrCgroupInode("", tmpFile.Name())
+	assert.Equal(t, "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa", cid)
+}
+
 func TestReadContainerID(t *testing.T) {
 	cid := "8c046cb0b72cd4c99f51b5591cd5b095967f58ee003710a45280c28ee1a9c7fa"
 	cgroupContents := "10:hugetlb:/kubepods/burstable/podfd52ef25-a87d-11e9-9423-0800271a638e/" + cid
@@ -57,7 +105,7 @@ func TestReadContainerID(t *testing.T) {
 	err = tmpFile.Close()
 	assert.NoError(t, err)
 
-	actualCID := readContainerID(tmpFile.Name())
+	actualCID := readContainerIDOrCgroupInode("", tmpFile.Name())
 	assert.Equal(t, cid, actualCID)
 }
 

statsd/statsd.go

@@ -453,7 +453,7 @@ func newWithWriter(w io.WriteCloser, o *Options, writerName string) (*Client, er
 	}
 
 	if !hasEntityID {
-		initContainerID(o.containerID, isOriginDetectionEnabled(o, hasEntityID))
+		initContainerIDOrCgroupInode(o.containerID, isOriginDetectionEnabled(o, hasEntityID))
 	}
 
 	if o.maxBytesPerPayload == 0 {

statsd/test_helpers_test.go

@@ -59,6 +59,7 @@ type testServer struct {
 	tags        string
 	namespace   string
 	containerID string
+	inode       string
 
 	aggregation         bool
 	extendedAggregation bool
@@ -328,6 +329,13 @@ func (ts *testServer) getContainerID() string {
 	return "|c:" + ts.containerID
 }
 
+func (ts *testServer) getCgroupInode() string {
+	if ts.inode == "" {
+		return ""
+	}
+	return "|e:" + ts.inode
+}
+
 func (ts *testServer) getFinalTelemetryTags() string {
 	base := "|#"
 	if ts.tags != "" {