feat: improved container-id parsing for ECS Fargate (#4216)

Refs: elastic/apm#888
Closes: #4215

Author: trentm

CHANGELOG.asciidoc

@@ -33,6 +33,25 @@ Notes:
 
 See the <<upgrade-to-v4>> guide.
 
+==== Unreleased
+
+[float]
+===== Breaking changes
+
+[float]
+===== Features
+
+- Minor improvement to container ID parsing from /etc/cgroup v1 files in
+  AWS ECS Fargate, where the pattern has been observed to sometimes differ
+  from the documented pattern. (https://github.com/elastic/apm/issues/888[APM spec issue #888])
+
+
+[float]
+===== Bug fixes
+
+[float]
+===== Chores
+
 
 [[release-notes-4.7.3]]
 ==== 4.7.3 - 2024/08/09

lib/apm-client/http-apm-client/container-info.js

@@ -12,7 +12,7 @@ const uuidSource =
   '[0-9a-f]{8}[-_][0-9a-f]{4}[-_][0-9a-f]{4}[-_][0-9a-f]{4}[-_][0-9a-f]{12}';
 const containerSource = '[0-9a-f]{64}';
 const taskSource = '[0-9a-f]{32}';
-const awsEcsSource = '[0-9a-f]{32}-[0-9]{10}';
+const awsEcsSource = '[0-9a-f]{32}-[0-9]{1,10}';
 
 const lineReg = /^(\d+):([^:]*):(.+)$/;
 const podReg = new RegExp(`pod(${uuidSource})(?:.slice)?$`);

test/apm-client/http-apm-client/container-info.test.js

@@ -265,6 +265,48 @@ tape.test('basics', (t) => {
     },
   );
 
+  // https://github.com/elastic/apm/issues/888 Fewer than ten digits observed
+  // for the suffix in ECS Fargate in the wild.
+  t.deepEqual(
+    parse(
+      '1:name=systemd:/ecs/46686c7c701cdfdf2549f88f7b9575e9/46686c7c701cdfdf2549f88f7b9575e9-123456789',
+      //                                                                                     ^^^^^^^^^
+    ),
+    {
+      entries: [
+        {
+          id: '1',
+          groups: 'name=systemd',
+          path: '/ecs/46686c7c701cdfdf2549f88f7b9575e9/46686c7c701cdfdf2549f88f7b9575e9-123456789',
+          controllers: ['name=systemd'],
+          taskId: '46686c7c701cdfdf2549f88f7b9575e9',
+        },
+      ],
+      containerId:
+        '34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376',
+      taskId: '46686c7c701cdfdf2549f88f7b9575e9',
+    },
+  );
+  t.deepEqual(
+    parse(
+      '1:name=systemd:/ecs/46686c7c701cdfdf2549f88f7b9575e9/46686c7c701cdfdf2549f88f7b9575e9-1',
+    ),
+    {
+      entries: [
+        {
+          id: '1',
+          groups: 'name=systemd',
+          path: '/ecs/46686c7c701cdfdf2549f88f7b9575e9/46686c7c701cdfdf2549f88f7b9575e9-1',
+          controllers: ['name=systemd'],
+          taskId: '46686c7c701cdfdf2549f88f7b9575e9',
+        },
+      ],
+      containerId:
+        '34dc0b5e626f2c5c4c5170e34b10e7654ce36f0fcd532739f4445baabea03376',
+      taskId: '46686c7c701cdfdf2549f88f7b9575e9',
+    },
+  );
+
   t.deepEqual(
     parse(`
     12:devices:/user.slice