From 2d2ba4521d2112ffdc78e044e6ce185ee114f2eb Mon Sep 17 00:00:00 2001
From: Philipp Muens <raute1337@gmx.de>
Date: Mon, 9 Jan 2017 11:15:12 -0800
Subject: [PATCH] Update Docker detection to be cgroup based

This ensures a more stable detection strategy since .dockerenv might be not around for the long term.
---
 lib/classes/Utils.js      |  6 +++---
 lib/classes/Utils.test.js | 12 +++++++-----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/lib/classes/Utils.js b/lib/classes/Utils.js
index 781b3891b..31fad2ae3 100644
--- a/lib/classes/Utils.js
+++ b/lib/classes/Utils.js
@@ -303,9 +303,9 @@ class Utils {
       // wrap in try catch to make sure that missing permissions won't break anything
       let isDockerContainer = false;
       try {
-        const dockerenvFile = '.dockerenv';
-        const dockerenvFilePath = path.join(this.getRootPath(), dockerenvFile);
-        isDockerContainer = this.fileExistsSync(dockerenvFilePath) || false;
+        const cgroupFilePath = path.join(this.getRootPath(), 'proc', '1', 'cgroup');
+        const cgroupFileContent = fs.readFileSync(cgroupFilePath).toString();
+        isDockerContainer = !!cgroupFileContent.match(/docker/);
       } catch (exception) {
         // do nothing
       }
diff --git a/lib/classes/Utils.test.js b/lib/classes/Utils.test.js
index cf758dc6e..8a404f61f 100644
--- a/lib/classes/Utils.test.js
+++ b/lib/classes/Utils.test.js
@@ -374,13 +374,15 @@ describe('Utils', () => {
     describe('when detecting Docker containers', () => {
       let rootPathStub;
       let rootDirPath;
-      let dockerenvFilePath;
+      let cgroupFilePath;
 
       beforeEach(() => {
         rootDirPath = testUtils.getTmpDirPath();
-        dockerenvFilePath = path.join(rootDirPath, '.dockerenv');
+        cgroupFilePath = path.join(rootDirPath, 'proc', '1', 'cgroup');
+        const cgroupFileContent = '6:devices:/docker/3601745b3bd54d9780436faa5f0e4f72';
         fse.mkdirsSync(rootDirPath);
-        fse.ensureFileSync(dockerenvFilePath);
+        fse.ensureFileSync(cgroupFilePath);
+        fs.writeFileSync(cgroupFilePath, cgroupFileContent);
 
         rootPathStub = sinon.stub(utils, 'getRootPath').returns(rootDirPath);
       });
@@ -404,8 +406,8 @@ describe('Utils', () => {
         })
       );
 
-      it('should not throw error if .dockerenv file is not accessible', () => {
-        fs.chmodSync(dockerenvFilePath, '000');
+      it('should not throw error if cgroup file is not accessible', () => {
+        fs.chmodSync(cgroupFilePath, '000');
         fs.chmodSync(rootDirPath, '400');
 
         utils.logStat(serverless).then(() => {