Docker ContainerID Support for CGroupV2

v3/internal/crossagent/cross_agent_tests/docker_container_id/cases.json

@@ -1,4 +1,9 @@
 [
+  {
+    "filename": "mountinfo.txt",
+    "containerId": "ec807d5258c06c355c07e2acb700f9029d820afe5836d6a7e19764773dc790f5",
+    "expectedMetrics": null
+  },
   {
     "filename": "docker-0.9.1.txt",
     "containerId": "f37a7e4d17017e7bf774656b19ca4360c6cdc4951c86700a464101d0d9ce97ee",

v3/internal/crossagent/cross_agent_tests/docker_container_id/mountinfo.txt

@@ -0,0 +1,21 @@
+787 677 0:205 / / rw,relatime master:211 - overlay overlay rw,lowerdir=/var/lib/docker/overlay2/l/4LWPEJQQP4ZTPKM5BERIGWX63N:/var/lib/docker/overlay2/l/TFA7XS7THOIUG2XOSPD63ZTVCW:/var/lib/docker/overlay2/l/LU2GER2CKIEZEN3O3ZM7MMN7FE:/var/lib/docker/overlay2/l/C56BBR5IUNPYU7VFQYBD7B6TRV:/var/lib/docker/overlay2/l/3H5SWJGWS5HFV3EVBSXW3Z5EWP:/var/lib/docker/overlay2/l/FZSKODSSYVKREFDR7EOHUS4C52:/var/lib/docker/overlay2/l/X4HBP5ZZCMRNDQROSJCS3FPJXN:/var/lib/docker/overlay2/l/YXPJDSIAVYL3AQXJOMJKC2UBQ7:/var/lib/docker/overlay2/l/S3H6KC6FPHLB4YMN24TNILEUIG:/var/lib/docker/overlay2/l/Y3UADAXTZUWRMXPRAFLWZEHC4O,upperdir=/var/lib/docker/overlay2/88a9371f4db27c41c3013cea0af17d1a51d8a591a659dafe0ee4f4f5aa07ea34/diff,workdir=/var/lib/docker/overlay2/88a9371f4db27c41c3013cea0af17d1a51d8a591a659dafe0ee4f4f5aa07ea34/work
+788 787 0:208 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw
+789 787 0:209 / /dev rw,nosuid - tmpfs tmpfs rw,size=65536k,mode=755
+790 789 0:210 / /dev/pts rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=666
+791 787 0:211 / /sys ro,nosuid,nodev,noexec,relatime - sysfs sysfs ro
+792 791 0:33 / /sys/fs/cgroup ro,nosuid,nodev,noexec,relatime - cgroup2 cgroup rw
+793 789 0:207 / /dev/mqueue rw,nosuid,nodev,noexec,relatime - mqueue mqueue rw
+794 789 0:212 / /dev/shm rw,nosuid,nodev,noexec,relatime - tmpfs shm rw,size=65536k
+795 787 254:1 /docker/containers/ec807d5258c06c355c07e2acb700f9029d820afe5836d6a7e19764773dc790f5/resolv.conf /etc/resolv.conf rw,relatime - ext4 /dev/vda1 rw
+796 787 254:1 /docker/containers/ec807d5258c06c355c07e2acb700f9029d820afe5836d6a7e19764773dc790f5/hostname /etc/hostname rw,relatime - ext4 /dev/vda1 rw
+797 787 254:1 /docker/containers/ec807d5258c06c355c07e2acb700f9029d820afe5836d6a7e19764773dc790f5/hosts /etc/hosts rw,relatime - ext4 /dev/vda1 rw
+678 788 0:208 /bus /proc/bus ro,nosuid,nodev,noexec,relatime - proc proc rw
+679 788 0:208 /fs /proc/fs ro,nosuid,nodev,noexec,relatime - proc proc rw
+680 788 0:208 /irq /proc/irq ro,nosuid,nodev,noexec,relatime - proc proc rw
+681 788 0:208 /sys /proc/sys ro,nosuid,nodev,noexec,relatime - proc proc rw
+682 788 0:208 /sysrq-trigger /proc/sysrq-trigger ro,nosuid,nodev,noexec,relatime - proc proc rw
+683 788 0:209 /null /proc/kcore rw,nosuid - tmpfs tmpfs rw,size=65536k,mode=755
+684 788 0:209 /null /proc/keys rw,nosuid - tmpfs tmpfs rw,size=65536k,mode=755
+685 788 0:209 /null /proc/timer_list rw,nosuid - tmpfs tmpfs rw,size=65536k,mode=755
+686 788 0:209 /null /proc/sched_debug rw,nosuid - tmpfs tmpfs rw,size=65536k,mode=755
+687 791 0:213 / /sys/firmware ro,relatime - tmpfs tmpfs ro

v3/internal/sysinfo/docker.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"regexp"
 	"runtime"
+	"strings"
 )
 
 var (
@@ -31,8 +32,18 @@ func DockerID() (string, error) {
 		return "", err
 	}
 	defer f.Close()
+	id, err := parseDockerID(f)
 
-	return parseDockerID(f)
+	// Attempt mountinfo file lookup if DockerID not found in cgroup file
+	if err == ErrDockerNotFound {
+		f, err := os.Open("/proc/self/mountinfo")
+		if err != nil {
+			return "", err
+		}
+		defer f.Close()
+		return parseDockerIDMountInfo(f)
+	}
+	return id, err
 }
 
 var (
@@ -43,6 +54,27 @@ var (
 	dockerIDRegex    = regexp.MustCompile(dockerIDRegexRaw)
 )
 
+func parseDockerIDMountInfo(r io.Reader) (string, error) {
+	// Each Line in the mountinfo file starts with a set of IDs before showing the path file we actually want
+	// 	1. Mount ID
+	//	2. Parent ID
+	//	3. Major and minor device numbers
+	// 	4. Path to ContainerID
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.Contains(line, "/docker/containers/") {
+			id := dockerIDRegex.FindString(line)
+			if err := validateDockerID(id); err != nil {
+				return "", err
+			}
+			return id, nil
+		}
+	}
+	return "", ErrDockerNotFound
+}
+
 func parseDockerID(r io.Reader) (string, error) {
 	// Each line in the cgroup file consists of three colon delimited fields.
 	//   1. hierarchy ID  - we don't care about this
@@ -51,7 +83,6 @@ func parseDockerID(r io.Reader) (string, error) {
 	//
 	// Example
 	//   5:cpuacct,cpu,cpuset:/daemons
-
 	var id string
 
 	for scanner := bufio.NewScanner(r); scanner.Scan(); {
@@ -77,7 +108,6 @@ func parseDockerID(r io.Reader) (string, error) {
 		}
 		return id, nil
 	}
-
 	return "", ErrDockerNotFound
 }
 

v3/internal/sysinfo/docker_test.go

@@ -33,7 +33,11 @@ func TestDockerIDCrossAgent(t *testing.T) {
 
 		got, _ := parseDockerID(bytes.NewReader(input))
 		if got != test.ID {
-			t.Errorf("%s != %s", got, test.ID)
+			mountInfoAttempt, _ := parseDockerIDMountInfo(bytes.NewReader(input))
+			if mountInfoAttempt != test.ID {
+				t.Errorf("MountInfo Attempt: %s != %s", mountInfoAttempt, test.ID)
+				t.Errorf("Traditional Attempt: %s != %s", got, test.ID)
+			}
 		}
 	}
 }