Use TCP keepalive probes to detect local log stream closing

Change-type: patch
Closes: #1219
Signed-off-by: Cameron Diver <cameron@balena.io>

lib/utils/device/api.ts

@@ -16,6 +16,8 @@
  */
 import * as Bluebird from 'bluebird';
 import * as _ from 'lodash';
+import { NodeJSSocketWithFileDescriptor } from 'net-keepalive';
+import * as os from 'os';
 import * as request from 'request';
 import * as Stream from 'stream';
 
@@ -175,7 +177,7 @@ export class DeviceAPI {
 		return new Bluebird((resolve, reject) => {
 			const req = request.get(url);
 
-			req.on('error', reject).on('response', res => {
+			req.on('error', reject).on('response', async res => {
 				if (res.statusCode !== 200) {
 					reject(
 						new ApiErrors.DeviceAPIError(
@@ -183,6 +185,18 @@ export class DeviceAPI {
 						),
 					);
 				}
+				res.socket.setKeepAlive(true, 1000);
+				if (os.platform() !== 'win32') {
+					const NetKeepalive = await import('net-keepalive');
+					// Certain versions of typescript won't convert
+					// this automatically
+					const sock = (res.socket as any) as NodeJSSocketWithFileDescriptor;
+					// We send a tcp keepalive probe once every 5 seconds
+					NetKeepalive.setKeepAliveInterval(sock, 5000);
+					// After 5 failed probes, the connection is marked as
+					// closed
+					NetKeepalive.setKeepAliveProbes(sock, 5);
+				}
 				resolve(res);
 			});
 		});

lib/utils/device/logs.ts

@@ -45,7 +45,10 @@ export function displayDeviceLogs(
 		});
 
 		logs.on('error', reject);
-		logs.on('end', resolve);
+		logs.on('end', () => {
+			logger.logError('Connection to device lost');
+			resolve();
+		});
 	});
 }
 

package.json

@@ -74,6 +74,7 @@
     "@types/lodash": "4.14.112",
     "@types/mixpanel": "2.14.0",
     "@types/mkdirp": "0.5.2",
+    "@types/net-keepalive": "^0.4.0",
     "@types/node": "6.14.2",
     "@types/prettyjson": "0.0.28",
     "@types/raven": "2.5.1",
@@ -186,6 +187,7 @@
     "window-size": "^1.1.0"
   },
   "optionalDependencies": {
+    "net-keepalive": "^1.2.1",
     "removedrive": "^1.0.0",
     "windosu": "^0.2.0"
   }