pre-flight checks before running CI

agent/lib/src/adb.dart

@@ -22,6 +22,10 @@ Future<Null> pickNextDevice() async {
   List<Adb> allDevices = (await Adb.deviceIds)
     .map((String id) => new Adb(deviceId: id))
     .toList();
+
+  if (allDevices.length == 0)
+    throw 'No Android devices detected';
+
   // TODO(yjbanov): filter out and warn about those with low battery level
   _currentDevice = allDevices[new math.Random().nextInt(allDevices.length)];
 }

agent/lib/src/agent.dart

@@ -37,9 +37,14 @@ class Agent {
   final Client httpClient;
 
   /// Makes a REST API request to Cocoon.
-  Future<dynamic> _cocoon(String apiPath, dynamic json) async {
+  Future<dynamic> _cocoon(String apiPath, [dynamic json]) async {
     String url = '$baseCocoonUrl/api/$apiPath';
-    Response resp = await httpClient.post(url, body: JSON.encode(json));
+    Response resp;
+    if (json != null) {
+      resp = await httpClient.post(url, body: JSON.encode(json));
+    } else {
+      resp = await httpClient.get(url);
+    }
     return JSON.decode(resp.body);
   }
 
@@ -121,6 +126,10 @@ class Agent {
       'NewStatus': newStatus,
     });
   }
+
+  Future<Map<String, dynamic>> getAuthenticationStatus() async {
+    return await _cocoon('get-authentication-status');
+  }
 }
 
 class AuthenticatedClient extends BaseClient {

agent/lib/src/commands/ci.dart

@@ -8,7 +8,9 @@ import 'dart:io';
 
 import 'package:args/args.dart';
 
+import '../adb.dart';
 import '../agent.dart';
+import '../firebase.dart';
 import '../utils.dart';
 
 /// Agents periodically poll the server for more tasks. This sleep period is
@@ -33,6 +35,7 @@ class ContinuousIntegrationCommand extends Command {
 
   @override
   Future<Null> run(ArgResults args) async {
+    await _performPreflightChecks();
     _listenToShutdownSignals();
     while(!_exiting) {
       try {
@@ -72,6 +75,19 @@ class ContinuousIntegrationCommand extends Command {
     }
   }
 
+  Future<Null> _performPreflightChecks() async {
+    print('Pre-flight checks:');
+    await pickNextDevice();
+    print('  - device connected');
+    await checkFirebaseConnection();
+    print('  - firebase connected');
+    if (!(await agent.getAuthenticationStatus())['Status'] == 'OK') {
+      throw 'Failed to authenticate to Cocoon. Check config.yaml.';
+    }
+    print('  - Cocoon auth OK');
+    print('Pre-flight OK');
+  }
+
   /// Listens to standard output and upload logs to Cocoon in semi-realtime.
   Future<Null> _logStandardStreams(CocoonTask task, Process proc) async {
     StringBuffer buffer = new StringBuffer();

agent/lib/src/firebase.dart

@@ -16,6 +16,12 @@ Firebase _measurements() {
       auth: firebaseToken);
 }
 
+Future<Null> checkFirebaseConnection() async {
+  if (await _measurements().child('dashboard_bot_status').child('current').get() == null) {
+    throw 'Connection to Firebase is unhealthy. Failed to read the current dashboard_bot_status entity.';
+  }
+}
+
 Future<Null> uploadToFirebase(String measurementKey, dynamic jsonData) async {
   Firebase ref = _measurements().child(measurementKey);
   await ref.child('current').set(jsonData);