fix: add docker container id discovery for SystemData

src/ElasticApm/Impl/MetadataDiscoverer.php

@@ -49,7 +49,7 @@ final class MetadataDiscoverer
     /** @var Logger */
     private $logger;
 
-    private function __construct(ConfigSnapshot $config, LoggerFactory $loggerFactory)
+    public function __construct(ConfigSnapshot $config, LoggerFactory $loggerFactory)
     {
         $this->config = $config;
         $this->logger = $loggerFactory->loggerForClass(LogCategory::BACKEND_COMM, __NAMESPACE__, __CLASS__, __FILE__);
@@ -130,6 +130,8 @@ public function discoverSystemData(ConfigSnapshot $config): SystemData
             }
         }
 
+        $containerId = $this->detectContainerId();
+
         return $result;
     }
 
@@ -143,6 +145,54 @@ public static function detectHostname(): ?string
         return Tracer::limitKeywordString($detected);
     }
 
+    private const DETECT_CONTAINER_ID_FILENAME_TI_REGEX = [
+        '/proc/self/mountinfo' => '/\/var\/lib\/docker\/containers\/([0-9a-f]+)\/hostname/m',
+        '/proc/self/cgroup' => '/\/docker\/([0-9a-f]+)$/m',
+    ];
+
+    /**
+     * @param callable(string $fileName): ?string $getFileContents
+     *
+     * @return ?string
+     */
+    public function detectContainerIdImpl(callable $getFileContents): ?string
+    {
+        foreach (self::DETECT_CONTAINER_ID_FILENAME_TI_REGEX as $fileName => $regex) {
+            if (($fileContents = $getFileContents($fileName)) !== null) {
+                if (preg_match($regex, $fileContents, $matches)) {
+                    return $matches[1];
+                }
+                ($loggerProxy = $this->logger->ifDebugLevelEnabled(__LINE__, __FUNCTION__))
+                && $loggerProxy->log('Could not find container ID in ' . $fileName, ['fileContents' => $fileContents, 'regex' => $regex]);
+            }
+        }
+
+        return null;
+    }
+
+    private function detectContainerIdGetFileContents(string $fileName): ?string
+    {
+        if (!file_exists($fileName)) {
+            ($loggerProxy = $this->logger->ifDebugLevelEnabled(__LINE__, __FUNCTION__)) && $loggerProxy->log('File ' . $fileName . ' does not exit');
+            return null;
+        }
+        $contents = file_get_contents($fileName);
+        if ($contents === false) {
+            ($loggerProxy = $this->logger->ifDebugLevelEnabled(__LINE__, __FUNCTION__)) && $loggerProxy->log('Failed to get ' . $fileName . ' contents');
+            return null;
+        }
+        return $contents;
+    }
+
+    private function detectContainerId(): ?string
+    {
+        return self::detectContainerIdImpl(
+            function (string $fileName): ?string {
+                return $this->detectContainerIdGetFileContents($fileName);
+            }
+        );
+    }
+
     public function buildNameVersionData(?string $name, ?string $version): NameVersionData
     {
         $result = new NameVersionData();

src/ElasticApm/Impl/SystemData.php

@@ -73,6 +73,17 @@ class SystemData implements SerializableDataInterface, LoggableInterface
      */
     public $configuredHostname = null;
 
+    /**
+     * @var string|null
+     *
+     * The length of this string is limited to 1024.
+     *
+     * Container ID.
+     *
+     * @link https://github.com/elastic/apm-server/blob/v7.4.0/docs/spec/system.json#L31
+     */
+    public $containerId = null;
+
     /** @inheritDoc */
     public function jsonSerialize()
     {
@@ -82,6 +93,11 @@ public function jsonSerialize()
         SerializationUtil::addNameValueIfNotNull('detected_hostname', $this->detectedHostname, /* ref */ $result);
         SerializationUtil::addNameValueIfNotNull('configured_hostname', $this->configuredHostname, /* ref */ $result);
 
+        if ($this->containerId !== null) {
+            $containerSubObject = ['id' => $this->containerId];
+            SerializationUtil::addNameValue('container', $containerSubObject, /* ref */ $result);
+        }
+
         return SerializationUtil::postProcessResult($result);
     }
 }

tests/ElasticApmTests/UnitTests/MetadataTest.php

@@ -25,8 +25,15 @@
 
 namespace ElasticApmTests\UnitTests;
 
+use Elastic\Apm\Impl\Log\NoopLoggerFactory;
 use Elastic\Apm\Impl\MetadataDiscoverer;
+use Elastic\Apm\Impl\Tracer;
+use ElasticApmTests\Util\AssertMessageStack;
+use ElasticApmTests\Util\DataProviderForTestBuilder;
+use ElasticApmTests\Util\MixedMap;
+use ElasticApmTests\Util\Pair;
 use ElasticApmTests\Util\TestCaseBase;
+use ElasticApmTests\Util\TracerBuilderForTests;
 
 class MetadataTest extends TestCaseBase
 {
@@ -39,4 +46,125 @@ public function testDefaultServiceNameUsesAgentName(): void
             MetadataDiscoverer::DEFAULT_SERVICE_NAME
         );
     }
+
+    private const FILE_NAME_TO_CONTENTS_KEY = 'file_name_to_contents';
+    private const PROC_SELF_MOUNTINFO_FILE_NAME = '/proc/self/mountinfo';
+    private const PROC_SELF_MOUNTINFO_CONTENTS_FROM_CONTAINER_KEY = 'proc_self_mountinfo_contents_from_container';
+    private const PROC_SELF_MOUNTINFO_CONTENTS_FROM_CONTAINER = '
+        857 856 0:61 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw
+        863 861 0:33 /docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df /sys/fs/cgroup/devices ro,nosuid,nodev,noexec,relatime master:15 - cgroup cgroup rw,devices
+        871 861 0:41 /docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df /sys/fs/cgroup/cpuset ro,nosuid,nodev,noexec,relatime master:23 - cgroup cgroup rw,cpuset
+        875 858 0:66 / /dev/shm rw,nosuid,nodev,noexec,relatime - tmpfs shm rw,size=65536k
+        876 856 8:5 /var/lib/docker/containers/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df/resolv.conf /etc/resolv.conf rw,relatime - ext4 /dev/sda5 rw,errors=remount-ro
+        877 856 8:5 /var/lib/docker/containers/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df/hostname /etc/hostname rw,relatime - ext4 /dev/sda5 rw,errors=remount-ro
+        878 856 8:5 /var/lib/docker/containers/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df/hosts /etc/hosts rw,relatime - ext4 /dev/sda5 rw,errors=remount-ro
+        674 857 0:61 /bus /proc/bus ro,nosuid,nodev,noexec,relatime - proc proc rw
+        675 857 0:61 /fs /proc/fs ro,nosuid,nodev,noexec,relatime - proc proc rw
+        676 857 0:61 /irq /proc/irq ro,nosuid,nodev,noexec,relatime - proc proc rw
+        677 857 0:61 /sys /proc/sys ro,nosuid,nodev,noexec,relatime - proc proc rw
+        ';
+    private const PROC_SELF_MOUNTINFO_CONTENTS_FROM_NON_CONTAINER_KEY = 'proc_self_mountinfo_contents_from_non_container';
+    private const PROC_SELF_MOUNTINFO_CONTENTS_FROM_NON_CONTAINER = '
+        24 29 0:22 / /sys rw,nosuid,nodev,noexec,relatime shared:7 - sysfs sysfs rw
+        25 29 0:23 / /proc rw,nosuid,nodev,noexec,relatime shared:14 - proc proc rw
+        26 29 0:5 / /dev rw,nosuid,noexec,relatime shared:2 - devtmpfs udev rw,size=1970232k,nr_inodes=492558,mode=755
+        28 29 0:25 / /run rw,nosuid,nodev,noexec,relatime shared:5 - tmpfs tmpfs rw,size=400072k,mode=755
+        29 1 8:5 / / rw,relatime shared:1 - ext4 /dev/sda5 rw,errors=remount-ro
+        193 29 7:21 / /snap/gnome-3-34-1804/93 ro,nodev,relatime shared:113 - squashfs /dev/loop21 ro
+        427 49 0:51 / /proc/sys/fs/binfmt_misc rw,nosuid,nodev,noexec,relatime shared:115 - binfmt_misc binfmt_misc rw
+        196 29 8:1 / /boot/efi rw,relatime shared:117 - vfat /dev/sda1 rw,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
+        ';
+    private const PROC_SELF_CGROUP_FILE_NAME = '/proc/self/cgroup';
+    private const PROC_SELF_CGROUP_CONTENTS_FROM_CONTAINER_KEY = 'proc_self_cgroup_contents_from_container';
+    private const PROC_SELF_CGROUP_CONTENTS_FROM_CONTAINER = '
+        10:cpuset:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        9:memory:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        8:pids:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        6:cpu,cpuacct:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        2:devices:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        1:name=systemd:/docker/c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df
+        0::/system.slice/containerd.service
+        ';
+    private const PROC_SELF_CGROUP_CONTENTS_FROM_NON_CONTAINER_KEY = 'proc_self_cgroup_contents_from_non_container';
+    private const PROC_SELF_CGROUP_CONTENTS_FROM_NON_CONTAINER = '
+        8:cpuset:/
+        7:pids:/user.slice/user-1000.slice/session-28.scope
+        6:memory:/user.slice/user-1000.slice/session-28.scope
+        4:devices:/user.slice
+        1:name=systemd:/user.slice/user-1000.slice/session-28.scope
+        0::/user.slice/user-1000.slice/session-28.scope
+        ';
+
+    private const FILE_CONTENTS_KEY_TO_CONTENTS
+        = [
+            self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_CONTAINER_KEY     => self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_CONTAINER,
+            self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_NON_CONTAINER_KEY => self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_NON_CONTAINER,
+            self::PROC_SELF_CGROUP_CONTENTS_FROM_CONTAINER_KEY        => self::PROC_SELF_CGROUP_CONTENTS_FROM_CONTAINER,
+            self::PROC_SELF_CGROUP_CONTENTS_FROM_NON_CONTAINER_KEY    => self::PROC_SELF_CGROUP_CONTENTS_FROM_NON_CONTAINER,
+        ];
+
+    private const EXPECTED_CONTAINER_ID_KEY = 'expected_container_id';
+    private const EXPECTED_CONTAINER_ID = 'c824705340063c4171d199fb6c95f94ff4966e29c77a7ad34d88b6f53a89f1df';
+
+    /**
+     * @return iterable<string, array{MixedMap}>
+     */
+    public static function dataProviderForTestDetectContainerId(): iterable
+    {
+        /**
+         * @return iterable<array<string, mixed>>
+         */
+        $generateDataSets = function (): iterable {
+            /** @var array<Pair<?string, bool>> $mountinfoVariants */
+            $mountinfoVariants = [
+                new Pair(self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_CONTAINER_KEY, true),
+                new Pair(self::PROC_SELF_MOUNTINFO_CONTENTS_FROM_NON_CONTAINER_KEY, false),
+                new Pair(null, false),
+            ];
+            /** @var array<Pair<?string, bool>> $cgroupVariants */
+            $cgroupVariants = [
+                new Pair(self::PROC_SELF_CGROUP_CONTENTS_FROM_CONTAINER_KEY, true),
+                new Pair(self::PROC_SELF_CGROUP_CONTENTS_FROM_NON_CONTAINER_KEY, false),
+                new Pair(null, false),
+            ];
+            $fileNameToContents = [];
+            foreach ($mountinfoVariants as $mountinfoVariant) {
+                $fileNameToContents[self::PROC_SELF_MOUNTINFO_FILE_NAME] = $mountinfoVariant->first;
+                foreach ($cgroupVariants as $cgroupVariant) {
+                    $fileNameToContents[self::PROC_SELF_CGROUP_FILE_NAME] = $cgroupVariant->first;
+                    yield [
+                        self::FILE_NAME_TO_CONTENTS_KEY => $fileNameToContents,
+                        self::EXPECTED_CONTAINER_ID_KEY => $mountinfoVariant->second || $cgroupVariant->second ? self::EXPECTED_CONTAINER_ID : null,
+                    ];
+                }
+            }
+        };
+
+        return DataProviderForTestBuilder::convertEachDataSetToMixedMapAndAddDesc($generateDataSets);
+    }
+
+    /**
+     * @dataProvider dataProviderForTestDetectContainerId
+     */
+    public function testDetectContainerId(MixedMap $testArgs): void
+    {
+        AssertMessageStack::newScope(/* out */ $dbgCtx, AssertMessageStack::funcArgs());
+        /** @var array<string, ?string> $fileNameToContentsKey */
+        $fileNameToContentsKey = $testArgs->getArray(self::FILE_NAME_TO_CONTENTS_KEY);
+        $expectedContainerId = $testArgs->getNullableString(self::EXPECTED_CONTAINER_ID_KEY);
+        $tracer = TracerBuilderForTests::startNew()->build();
+        self::assertInstanceOf(Tracer::class, $tracer);
+        $actualContainerId = (new MetadataDiscoverer($tracer->getConfig(), NoopLoggerFactory::singletonInstance()))->detectContainerIdImpl(
+            function (string $fileName) use ($fileNameToContentsKey): ?string {
+                self::assertArrayHasKey($fileName, $fileNameToContentsKey);
+                $fileContentsKey = $fileNameToContentsKey[$fileName];
+                if ($fileContentsKey === null) {
+                    return null;
+                }
+                self::assertArrayHasKey($fileContentsKey, self::FILE_CONTENTS_KEY_TO_CONTENTS);
+                return self::FILE_CONTENTS_KEY_TO_CONTENTS[$fileContentsKey];
+            }
+        );
+        self::assertSame($expectedContainerId, $actualContainerId);
+    }
 }

tests/ElasticApmTests/Util/Deserialization/MetadataDeserializer.php

@@ -208,6 +208,9 @@ function ($key, $value) use ($result): bool {
                     case 'configured_hostname':
                         $result->configuredHostname = self::assertValidKeywordString($value);
                         return true;
+                    case 'container':
+                        self::deserializeContainer($value, $result);
+                        return true;
                     default:
                         return false;
                 }
@@ -217,6 +220,26 @@ function ($key, $value) use ($result): bool {
         return $result;
     }
 
+    /**
+     * @param mixed      $value
+     * @param SystemData $result
+     */
+    private static function deserializeContainer($value, SystemData $result): void
+    {
+        DeserializationUtil::deserializeKeyValuePairs(
+            DeserializationUtil::assertDecodedJsonMap($value),
+            function ($key, $value) use ($result): bool {
+                switch ($key) {
+                    case 'id':
+                        $result->containerId = self::assertValidKeywordString($value);
+                        return true;
+                    default:
+                        return false;
+                }
+            }
+        );
+    }
+
     /**
      * @param mixed $value
      *