Modify spec for cgroups v2 container ID parsing

specs/agents/metadata.md

@@ -112,6 +112,17 @@ If the Kubernetes pod name is not the hostname, it can be overridden by the `KUB
 
 *Note:* [cgroup_parsing.json](../../tests/agents/json-specs/cgroup_parsing.json) provides test cases for parsing cgroup lines.
 
+With cgroups v2, the `/proc/self/cgroup does not contain the container ID and we have to parse the `/proc/self/mounts` with the following algorithm:
+
+ 1. filter the line containing `/etc/hostname` to retrieve the file mount that provides the host name to the container.
+
+ 2. split the line on spaces and take the 3rd element containing the host path.
+
+ 3. extract the container ID from file path by using a regular expression matching a 64 character hexadecimal ID.
+
+*Note:* [mounts_parsing.json](../../tests/agents/json-specs/múnts_parsing.json) provides a test case for parsing mounts lines.
+
+
 ### Process metadata
 
 Process level metadata relates to the process running the service being monitored:

tests/agents/json-specs/mounts_parsing.json

@@ -0,0 +1,21 @@
+{
+  "lines": [
+    "3984 3905 0:73 / / rw,relatime shared:1863 master:1733 - overlay overlay rw,lowerdir=/var/lib/docker/overlay2/l/KEX7CWLHQCXQY2RHPGTXJ3C26N:/var/lib/docker/overlay2/l/2PVS7JRTRSTVZS4KSUAFML3BIV:/var/lib/docker/overlay2/l/52M7ARM4JDVHCJAYUI6JIKBO4B,upperdir=/var/lib/docker/overlay2/267f825fb89e584605bf161177451879c0ba8b15f7df9b51fb7843c7beb9ed25/diff,workdir=/var/lib/docker/overlay2/267f825fb89e584605bf161177451879c0ba8b15f7df9b51fb7843c7beb9ed25/work",
+    "3985 3984 0:77 / /proc rw,nosuid,nodev,noexec,relatime shared:1864 - proc proc rw",
+    "3986 3984 0:78 / /dev rw,nosuid shared:1865 - tmpfs tmpfs rw,size=65536k,mode=755,inode64",
+    "3987 3986 0:79 / /dev/pts rw,nosuid,noexec,relatime shared:1866 - devpts devpts rw,gid=5,mode=620,ptmxmode=666",
+    "3988 3984 0:80 / /sys ro,nosuid,nodev,noexec,relatime shared:1870 - sysfs sysfs ro",
+    "3989 3988 0:30 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime shared:1871 - cgroup2 cgroup rw",
+    "3990 3986 0:76 / /dev/mqueue rw,nosuid,nodev,noexec,relatime shared:1867 - mqueue mqueue rw",
+    "3991 3986 0:81 / /dev/shm rw,nosuid,nodev,noexec,relatime shared:1868 - tmpfs shm rw,size=65536k,inode64",
+    "3992 3984 253:1 /var/lib/docker/volumes/9d18ce5b36572d85358fa936afe5a4bf95cca5c822b04941aa08c6118f6e0d33/_data /var rw,relatime shared:1872 master:1 - ext4 /dev/mapper/vgubuntu-root rw,errors=remount-ro",
+    "3993 3984 0:82 / /run rw,nosuid,nodev,noexec,relatime shared:1873 - tmpfs tmpfs rw,inode64",
+    "3994 3984 0:83 / /tmp rw,nosuid,nodev,noexec,relatime shared:1874 - tmpfs tmpfs rw,inode64",
+    "3995 3984 253:1 /usr/lib/modules /usr/lib/modules ro,relatime shared:1875 - ext4 /dev/mapper/vgubuntu-root rw,errors=remount-ro",
+    "3996 3984 253:1 /var/lib/docker/containers/6548c6863fb748e72d1e2a4f824fde92f720952d062dede1318c2d6219a672d6/resolv.conf /etc/resolv.conf rw,relatime shared:1876 - ext4 /dev/mapper/vgubuntu-root rw,errors=remount-ro",
+    "3997 3984 253:1 /var/lib/docker/containers/6548c6863fb748e72d1e2a4f824fde92f720952d062dede1318c2d6219a672d6/hostname /etc/hostname rw,relatime shared:1877 - ext4 /dev/mapper/vgubuntu-root rw,errors=remount-ro",
+    "3998 3984 253:1 /var/lib/docker/containers/6548c6863fb748e72d1e2a4f824fde92f720952d062dede1318c2d6219a672d6/hosts /etc/hosts rw,relatime shared:1878 - ext4 /dev/mapper/vgubuntu-root rw,errors=remount-ro"
+  ],
+  "containerId": "6548c6863fb748e72d1e2a4f824fde92f720952d062dede1318c2d6219a672d6"
+}
+