parse container ID with cgroups v2

.ci/updatecli.d/update-json-specs.yml

@@ -24,10 +24,10 @@ sources:
       - findsubmatch:
           pattern: "[0-9a-f]{40}"
 
-  cgroup_parsing.json:
+  container_metadata_discovery.json:
     kind: file
     spec:
-      file: https://raw.githubusercontent.com/elastic/apm/main/tests/agents/json-specs/cgroup_parsing.json
+      file: https://raw.githubusercontent.com/elastic/apm/main/tests/agents/json-specs/container_metadata_discovery.json
   service_resource_inference.json:
     kind: file
     spec:
@@ -70,13 +70,13 @@ actions:
         * https://github.com/elastic/apm/commit/{{ source "sha" }}
 
 targets:
-  cgroup_parsing.json:
-    name: cgroup_parsing.json
+  container_metadata_discovery.json:
+    name: container_metadata_discovery.json
     scmid: default
-    sourceid: cgroup_parsing.json
+    sourceid: container_metadata_discovery.json
     kind: file
     spec:
-      file: apm-agent-core/src/test/resources/json-specs/cgroup_parsing.json
+      file: apm-agent-core/src/test/resources/json-specs/container_metadata_discovery.json
   service_resource_inference.json:
     name: service_resource_inference.json
     scmid: default

CHANGELOG.asciidoc

@@ -31,6 +31,10 @@ Use subheadings with the "=====" level for adding notes for unreleased changes:
 
 === Unreleased
 
+[float]
+===== Features
+* Capture `container.id` for cgroups v2 - {pull}3199[#3199]
+
 [float]
 ===== Bug fixes
 * Fixed agent programmatic attach with immutable config - {pull}3170[#3170]

apm-agent-core/src/main/java/co/elastic/apm/agent/impl/metadata/SystemInfo.java

@@ -45,11 +45,18 @@
 public class SystemInfo {
     private static final Logger logger = LoggerFactory.getLogger(SystemInfo.class);
 
-    private static final String CONTAINER_UID_REGEX = "^[0-9a-fA-F]{64}$";
+    private static final String CONTAINER_REGEX_64 = "[0-9a-fA-F]{64}";
+    private static final String CONTAINER_UID_REGEX = "^" + CONTAINER_REGEX_64 + "$";
     private static final String SHORTENED_UUID_PATTERN = "^[0-9a-fA-F]{8}\\-[0-9a-fA-F]{4}\\-[0-9a-fA-F]{4}\\-[0-9a-fA-F]{4}\\-[0-9a-fA-F]{4,}";
     private static final String AWS_FARGATE_UID_REGEX = "^[0-9a-fA-F]{32}\\-[0-9]{10}$";
     private static final String POD_REGEX = "(?:^/kubepods[\\S]*/pod([^/]+)$)|(?:kubepods[^/]*-pod([^/]+)\\.slice)";
 
+    private static final String CGROUPV2_HOSTNAME_FILE = "/etc/hostname";
+    private static final Pattern CGROUPV2_CONTAINER_PATTERN = Pattern.compile("^.*(" + CONTAINER_REGEX_64 + ").*$");
+
+    private static final String SELF_CGROUP = "/proc/self/cgroup";
+    private static final String SELF_MOUNTINFO = "/proc/self/mountinfo";
+
     /**
      * Architecture of the system the agent is running on.
      */
@@ -58,6 +65,7 @@ public class SystemInfo {
     /**
      * Hostname configured manually through {@link co.elastic.apm.agent.configuration.CoreConfiguration#hostname}.
      */
+    @SuppressWarnings("JavadocReference")
     @Nullable
     private final String configuredHostname;
 
@@ -101,11 +109,13 @@ public SystemInfo(String architecture, @Nullable String configuredHostname, @Nul
     /**
      * Creates a {@link SystemInfo} containing auto-discovered info about the system.
      * This method may block on reading files and executing external processes.
-     * @param configuredHostname hostname configured through the {@link co.elastic.apm.agent.configuration.CoreConfiguration#hostname} config
-     * @param timeoutMillis enables to limit the execution of the system discovery task
+     *
+     * @param configuredHostname      hostname configured through the {@link co.elastic.apm.agent.configuration.CoreConfiguration#hostname} config
+     * @param timeoutMillis           enables to limit the execution of the system discovery task
      * @param serverlessConfiguration serverless config
      * @return a future from which this system's info can be obtained
      */
+    @SuppressWarnings("JavadocReference")
     public static SystemInfo create(final @Nullable String configuredHostname, final long timeoutMillis, ServerlessConfiguration serverlessConfiguration) {
         final String osName = System.getProperty("os.name");
         final String osArch = System.getProperty("os.arch");
@@ -136,7 +146,8 @@ static boolean isWindows(String osName) {
      * Discover the current host's name. This method separates operating systems only to Windows and non-Windows,
      * both in the executed hostname-discovery-command and the fallback environment variables.
      * It always starts with execution of a command on an external process, so it may block up to the specified timeout.
-     * @param isWindows used to decide how hostname discovery should be executed
+     *
+     * @param isWindows     used to decide how hostname discovery should be executed
      * @param timeoutMillis limits the time this method may block on executing external commands
      * @return the discovered hostname
      */
@@ -182,7 +193,8 @@ static String discoverHostnameThroughCommand(boolean isWindows, long timeoutMill
     /**
      * Tries to discover the current host name by executing the provided command in a spawned process.
      * This method may block up to the specified timeout, waiting for the spawned process to terminate.
-     * @param cmd the hostname discovery command
+     *
+     * @param cmd           the hostname discovery command
      * @param timeoutMillis maximum time to allow to the provided command to execute
      * @return the discovered hostname
      */
@@ -246,21 +258,9 @@ static String discoverHostnameThroughEnv(boolean isWindows) {
      * @return container ID parsed from {@code /proc/self/cgroup} file lines, or {@code null} if can't find/read/parse file lines
      */
     SystemInfo findContainerDetails() {
-        String containerId = null;
-        try {
-            Path path = FileSystems.getDefault().getPath("/proc/self/cgroup");
-            if (path.toFile().exists()) {
-                List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
-                for (final String line : lines) {
-                    parseContainerId(line);
-                    if (container != null) {
-                        containerId = container.getId();
-                        break;
-                    }
-                }
-            }
-        } catch (Throwable e) {
-            logger.warn("Failed to read/parse container ID from '/proc/self/cgroup'", e);
+        parseCgroupsFile(FileSystems.getDefault().getPath(SELF_CGROUP));
+        if (container == null) {
+            parseMountInfo(FileSystems.getDefault().getPath(SELF_MOUNTINFO));
         }
 
         try {
@@ -284,29 +284,68 @@ SystemInfo findContainerDetails() {
             logger.warn("Failed to read environment variables for Kubernetes Downward API discovery", e);
         }
 
-        logger.debug("container ID is {}", containerId);
+        logger.debug("container ID is {}", container != null ? container.getId() : null);
         return this;
     }
 
+    @Nullable
+    private void parseMountInfo(Path path) {
+        if (!Files.isRegularFile(path)) {
+            logger.debug("Could not parse container ID from '{}'", path);
+            return;
+        }
+        try {
+            List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
+            parseCgroupsV2ContainerId(lines);
+            if (container != null) {
+                return;
+            }
+            logger.debug("Could not parse container ID from '{}' lines: {}", path, lines);
+        } catch (Throwable e) {
+            logger.warn(String.format("Failed to read/parse container ID from '%s'", path), e);
+        }
+    }
+
+    @Nullable
+    private void parseCgroupsFile(Path path) {
+        if(!Files.isRegularFile(path)){
+            logger.debug("Could not parse container ID from '{}'", path);
+            return;
+        }
+        try {
+            List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
+            for (String line : lines) {
+                parseCgroupsLine(line);
+                if (container != null) {
+                    return;
+                }
+            }
+        } catch (Throwable e) {
+            logger.warn(String.format("Failed to read/parse container ID from '%s'", path), e);
+        }
+    }
+
     /**
      * The virtual file /proc/self/cgroup lists the control groups that the process is a member of. Each line contains
      * three colon-separated fields of the form hierarchy-ID:subsystem-list:cgroup-path.
-     *
+     * <p>
      * Depending on the filesystem driver used for cgroup management, the cgroup-path will have
      * one of the following formats in a Docker container:
-     *
-     * 		systemd: /system.slice/docker-<container-ID>.scope
-     * 		cgroupfs: /docker/<container-ID>
-     *
-     * 	In a Kubernetes pod, the cgroup path will look like:
-     *
-     * 		systemd: /kubepods.slice/kubepods-<QoS-class>.slice/kubepods-<QoS-class>-pod<pod-UID>.slice/<container-iD>.scope
-     * 		cgroupfs: /kubepods/<QoS-class>/pod<pod-UID>/<container-iD>
+     * </p>
+     * <pre>
+     *   systemd: /system.slice/docker-<container-ID>.scope
+     *   cgroupfs: /docker/<container-ID>
+     * </pre>
+     * In a Kubernetes pod, the cgroup path will look like:
+     * <pre>
+     *   systemd: /kubepods.slice/kubepods-<QoS-class>.slice/kubepods-<QoS-class>-pod<pod-UID>.slice/<container-iD>.scope
+     *   cgroupfs: /kubepods/<QoS-class>/pod<pod-UID>/<container-iD>
+     * </pre
      *
      * @param line a line from the /proc/self/cgroup file
      * @return this SystemInfo object after parsing
      */
-    SystemInfo parseContainerId(String line) {
+    SystemInfo parseCgroupsLine(String line) {
         final String[] fields = line.split(":", 3);
         if (fields.length == 3) {
             String cGroupPath = fields[2];
@@ -351,14 +390,38 @@ SystemInfo parseContainerId(String line) {
                 if (kubernetes != null ||
                     idPart.matches(CONTAINER_UID_REGEX) ||
                     idPart.matches(SHORTENED_UUID_PATTERN) ||
-                    idPart.matches(AWS_FARGATE_UID_REGEX))  {
+                    idPart.matches(AWS_FARGATE_UID_REGEX)) {
                     container = new Container(idPart);
                 }
             }
         }
         if (container == null) {
-            logger.debug("Could not parse container ID from '/proc/self/cgroup' line: {}", line);
+            logger.debug("Could not parse container ID from line: {}", line);
+        }
+        return this;
+    }
+
+    /**
+     * @param lines lines from the /proc/self/mountinfo file
+     * @return this SystemInfo object after parsing
+     */
+    SystemInfo parseCgroupsV2ContainerId(List<String> lines) {
+        for (String line : lines) {
+            int index = line.indexOf(CGROUPV2_HOSTNAME_FILE);
+            if (index > 0) {
+                String[] parts = line.split(" ");
+                if (parts.length > 3) {
+                    Matcher matcher = CGROUPV2_CONTAINER_PATTERN.matcher(parts[3]);
+                    if (matcher.matches() && matcher.groupCount() == 1) {
+                        container = new Container(matcher.group(1));
+                    }
+                }
+            }
         }
+
+
+
+
         return this;
     }
 
@@ -373,23 +436,26 @@ public String getArchitecture() {
      * Returns the hostname. If a non-empty hostname was configured manually, it will be returned.
      * Otherwise, the automatically discovered hostname will be returned.
      * If both are null or empty, this method returns {@code <unknown>}.
+     *
      * @deprecated should only be used when communicating to APM Server of version lower than 7.4
      */
-     @Deprecated
+    @Deprecated
     public String getHostname() {
-         if (configuredHostname != null && !configuredHostname.isEmpty()) {
-             return configuredHostname;
-         }
-         if (detectedHostname != null && !detectedHostname.isEmpty()) {
-             return detectedHostname;
-         }
-         return "<unknown>";
+        if (configuredHostname != null && !configuredHostname.isEmpty()) {
+            return configuredHostname;
+        }
+        if (detectedHostname != null && !detectedHostname.isEmpty()) {
+            return detectedHostname;
+        }
+        return "<unknown>";
     }
 
     /**
      * The hostname manually configured through {@link co.elastic.apm.agent.configuration.CoreConfiguration#hostname}
+     *
      * @return the manually configured hostname
      */
+    @SuppressWarnings("JavadocReference")
     @Nullable
     public String getConfiguredHostname() {
         return configuredHostname;
@@ -431,7 +497,7 @@ public Kubernetes getKubernetesInfo() {
     }
 
     public static class Container {
-        private String id;
+        private final String id;
 
         Container(String id) {
             this.id = id;