Support cgroup v2 (#7167)

This resolves #6694. We've been tracking the update to cgroup version support and want to get ahead of the widespread usage. The surface of the existing `ContainerResource` has not changed, but its internals have been factored out to two "extractor" utilities -- one that understands cgroup v1 and another for v2. v1 is attempted and, if successful, the result is used. If v1 fails, then the `ContainerResource` will fall back to v2. As mentioned in #6694, the approach taken in this PR is borrowed from [this SO post](https://stackoverflow.com/questions/68816329/how-to-get-docker-container-id-from-within-the-container-with-cgroup-v2) combined with local experimentation on docker desktop on a Mac, which already uses cgroup2 v2.
open-telemetry · Nov 15, 2022 · b09fb67 · b09fb67
1 parent 33b0b58
commit b09fb67
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diff --git a/...rc/main/java/io/opentelemetry/instrumentation/resources/CgroupV1ContainerIdExtractor.java b/...rc/main/java/io/opentelemetry/instrumentation/resources/CgroupV1ContainerIdExtractor.java
@@ -0,0 +1,95 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.resources;
+
+import io.opentelemetry.api.internal.OtelEncodingUtils;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.stream.Stream;
+
+/** Utility for extracting the container ID from runtimes inside cgroup v1 containers. */
+final class CgroupV1ContainerIdExtractor {
+
+  private static final Logger logger =
+      Logger.getLogger(CgroupV1ContainerIdExtractor.class.getName());
+  static final Path V1_CGROUP_PATH = Paths.get("/proc/self/cgroup");
+  private final ContainerResource.Filesystem filesystem;
+
+  CgroupV1ContainerIdExtractor() {
+    this(ContainerResource.FILESYSTEM_INSTANCE);
+  }
+
+  // Exists for testing
+  CgroupV1ContainerIdExtractor(ContainerResource.Filesystem filesystem) {
+    this.filesystem = filesystem;
+  }
+
+  /**
+   * Each line of cgroup file looks like "14:name=systemd:/docker/.../... A hex string is expected
+   * inside the last section separated by '/' Each segment of the '/' can contain metadata separated
+   * by either '.' (at beginning) or '-' (at end)
+   *
+   * @return containerId
+   */
+  Optional<String> extractContainerId() {
+    if (!filesystem.isReadable(V1_CGROUP_PATH)) {
+      return Optional.empty();
+    }
+    try (Stream<String> lines = filesystem.lines(V1_CGROUP_PATH)) {
+      return lines
+          .filter(line -> !line.isEmpty())
+          .map(CgroupV1ContainerIdExtractor::getIdFromLine)
+          .filter(Optional::isPresent)
+          .findFirst()
+          .orElse(Optional.empty());
+    } catch (Exception e) {
+      logger.log(Level.WARNING, "Unable to read file", e);
+    }
+    return Optional.empty();
+  }
+
+  private static Optional<String> getIdFromLine(String line) {
+    // This cgroup output line should have the container id in it
+    int lastSlashIdx = line.lastIndexOf('/');
+    if (lastSlashIdx < 0) {
+      return Optional.empty();
+    }
+
+    String containerId;
+
+    String lastSection = line.substring(lastSlashIdx + 1);
+    int colonIdx = lastSection.lastIndexOf(':');
+
+    if (colonIdx != -1) {
+      // since containerd v1.5.0+, containerId is divided by the last colon when the cgroupDriver is
+      // systemd:
+      // https://github.com/containerd/containerd/blob/release/1.5/pkg/cri/server/helpers_linux.go#L64
+      containerId = lastSection.substring(colonIdx + 1);
+    } else {
+      int startIdx = lastSection.lastIndexOf('-');
+      int endIdx = lastSection.lastIndexOf('.');
+
+      startIdx = startIdx == -1 ? 0 : startIdx + 1;
+      if (endIdx == -1) {
+        endIdx = lastSection.length();
+      }
+      if (startIdx > endIdx) {
+        return Optional.empty();
+      }
+
+      containerId = lastSection.substring(startIdx, endIdx);
+    }
+
+    if (OtelEncodingUtils.isValidBase16String(containerId) && !containerId.isEmpty()) {
+      return Optional.of(containerId);
+    } else {
+      return Optional.empty();
+    }
+  }
+}
diff --git a/...rc/main/java/io/opentelemetry/instrumentation/resources/CgroupV2ContainerIdExtractor.java b/...rc/main/java/io/opentelemetry/instrumentation/resources/CgroupV2ContainerIdExtractor.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.resources;
+
+import static java.util.Optional.empty;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Optional;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/** Utility for extracting the container ID from runtimes inside cgroup v2 containers. */
+class CgroupV2ContainerIdExtractor {
+
+  private static final Logger logger =
+      Logger.getLogger(CgroupV2ContainerIdExtractor.class.getName());
+
+  static final Path V2_CGROUP_PATH = Paths.get("/proc/self/mountinfo");
+  private static final Pattern CONTAINER_RE =
+      Pattern.compile(".*/docker/containers/([0-9a-f]{64})/.*");
+
+  private final ContainerResource.Filesystem filesystem;
+
+  CgroupV2ContainerIdExtractor() {
+    this(ContainerResource.FILESYSTEM_INSTANCE);
+  }
+
+  // Exists for testing
+  CgroupV2ContainerIdExtractor(ContainerResource.Filesystem filesystem) {
+    this.filesystem = filesystem;
+  }
+
+  Optional<String> extractContainerId() {
+    if (!filesystem.isReadable(V2_CGROUP_PATH)) {
+      return empty();
+    }
+    try {
+      return filesystem
+          .lines(V2_CGROUP_PATH)
+          .map(CONTAINER_RE::matcher)
+          .filter(Matcher::matches)
+          .findFirst()
+          .map(matcher -> matcher.group(1));
+    } catch (IOException e) {
+      logger.log(Level.WARNING, "Unable to read v2 cgroup path", e);
+    }
+    return empty();
+  }
+}
diff --git a/...s/library/src/main/java/io/opentelemetry/instrumentation/resources/ContainerResource.java b/...s/library/src/main/java/io/opentelemetry/instrumentation/resources/ContainerResource.java
@@ -5,106 +5,75 @@
 
 package io.opentelemetry.instrumentation.resources;
 
+import static io.opentelemetry.semconv.resource.attributes.ResourceAttributes.CONTAINER_ID;
+
+import com.google.errorprone.annotations.MustBeClosed;
 import io.opentelemetry.api.common.Attributes;
-import io.opentelemetry.api.internal.OtelEncodingUtils;
 import io.opentelemetry.sdk.resources.Resource;
-import io.opentelemetry.semconv.resource.attributes.ResourceAttributes;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.Optional;
-import java.util.logging.Level;
-import java.util.logging.Logger;
 import java.util.stream.Stream;
 
-/** Factory for {@link Resource} retrieving Container ID information. */
+/**
+ * Factory for {@link Resource} retrieving Container ID information. It supports both cgroup v1 and
+ * v2 runtimes.
+ */
 public final class ContainerResource {
 
-  private static final Logger logger = Logger.getLogger(ContainerResource.class.getName());
-  private static final String UNIQUE_HOST_NAME_FILE_NAME = "/proc/self/cgroup";
-  private static final Resource INSTANCE = buildSingleton(UNIQUE_HOST_NAME_FILE_NAME);
+  static final Filesystem FILESYSTEM_INSTANCE = new Filesystem();
+  private static final Resource INSTANCE = buildSingleton();
 
-  private static Resource buildSingleton(String uniqueHostNameFileName) {
+  private static Resource buildSingleton() {
     // can't initialize this statically without running afoul of animalSniffer on paths
-    return buildResource(Paths.get(uniqueHostNameFileName));
+    return new ContainerResource().buildResource();
   }
 
-  // package private for testing
-  static Resource buildResource(Path path) {
-    return extractContainerId(path)
-        .map(
-            containerId ->
-                Resource.create(Attributes.of(ResourceAttributes.CONTAINER_ID, containerId)))
-        .orElseGet(Resource::empty);
+  private final CgroupV1ContainerIdExtractor v1Extractor;
+  private final CgroupV2ContainerIdExtractor v2Extractor;
+
+  private ContainerResource() {
+    this(new CgroupV1ContainerIdExtractor(), new CgroupV2ContainerIdExtractor());
   }
 
-  /** Returns resource with container information. */
-  public static Resource get() {
-    return INSTANCE;
+  // Visible for testing
+  ContainerResource(
+      CgroupV1ContainerIdExtractor v1Extractor, CgroupV2ContainerIdExtractor v2Extractor) {
+    this.v1Extractor = v1Extractor;
+    this.v2Extractor = v2Extractor;
   }
 
-  /**
-   * Each line of cgroup file looks like "14:name=systemd:/docker/.../... A hex string is expected
-   * inside the last section separated by '/' Each segment of the '/' can contain metadata separated
-   * by either '.' (at beginning) or '-' (at end)
-   *
-   * @return containerId
-   */
-  private static Optional<String> extractContainerId(Path cgroupFilePath) {
-    if (!Files.exists(cgroupFilePath) || !Files.isReadable(cgroupFilePath)) {
-      return Optional.empty();
-    }
-    try (Stream<String> lines = Files.lines(cgroupFilePath)) {
-      return lines
-          .filter(line -> !line.isEmpty())
-          .map(ContainerResource::getIdFromLine)
-          .filter(Optional::isPresent)
-          .findFirst()
-          .orElse(Optional.empty());
-    } catch (Exception e) {
-      logger.log(Level.WARNING, "Unable to read file", e);
-    }
-    return Optional.empty();
+  // Visible for testing
+  Resource buildResource() {
+    return getContainerId()
+        .map(id -> Resource.create(Attributes.of(CONTAINER_ID, id)))
+        .orElseGet(Resource::empty);
   }
 
-  private static Optional<String> getIdFromLine(String line) {
-    // This cgroup output line should have the container id in it
-    int lastSlashIdx = line.lastIndexOf('/');
-    if (lastSlashIdx < 0) {
-      return Optional.empty();
+  private Optional<String> getContainerId() {
+    Optional<String> v1Result = v1Extractor.extractContainerId();
+    if (v1Result.isPresent()) {
+      return v1Result;
     }
+    return v2Extractor.extractContainerId();
+  }
 
-    String containerId;
-
-    String lastSection = line.substring(lastSlashIdx + 1);
-    int colonIdx = lastSection.lastIndexOf(':');
-
-    if (colonIdx != -1) {
-      // since containerd v1.5.0+, containerId is divided by the last colon when the cgroupDriver is
-      // systemd:
-      // https://github.com/containerd/containerd/blob/release/1.5/pkg/cri/server/helpers_linux.go#L64
-      containerId = lastSection.substring(colonIdx + 1);
-    } else {
-      int startIdx = lastSection.lastIndexOf('-');
-      int endIdx = lastSection.lastIndexOf('.');
+  /** Returns resource with container information. */
+  public static Resource get() {
+    return INSTANCE;
+  }
 
-      startIdx = startIdx == -1 ? 0 : startIdx + 1;
-      if (endIdx == -1) {
-        endIdx = lastSection.length();
-      }
-      if (startIdx > endIdx) {
-        return Optional.empty();
-      }
+  // Exists for testing
+  static class Filesystem {
 
-      containerId = lastSection.substring(startIdx, endIdx);
+    boolean isReadable(Path path) {
+      return Files.isReadable(path);
     }
 
-    if (OtelEncodingUtils.isValidBase16String(containerId) && !containerId.isEmpty()) {
-      return Optional.of(containerId);
-    } else {
-      return Optional.empty();
+    @MustBeClosed
+    Stream<String> lines(Path path) throws IOException {
+      return Files.lines(path);
     }
   }
-
-  private ContainerResource() {}
 }