[RPC] android process isolation/watchdog (apache#1387)

apps/android_rpc/app/src/main/AndroidManifest.xml

@@ -2,11 +2,14 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="ml.dmlc.tvm.tvmrpc" >
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:label="@string/app_name"
         android:supportsRtl="true"
-        android:theme="@style/AppTheme" >
+        android:theme="@style/AppTheme"
+        android:icon="@mipmap/ic_launcher" >
         <activity
             android:name=".MainActivity"
             android:label="@string/app_name"
@@ -17,8 +20,9 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+        <service android:name=".RPCService"
+                 android:process=":RPCServiceProcess"
+                 android:permission="android.permission.BIND_JOB_SERVICE" />
     </application>
 
-    <uses-permission android:name="android.permission.INTERNET" />
-
-</manifest>
+</manifest>

apps/android_rpc/app/src/main/java/ml/dmlc/tvm/tvmrpc/MainActivity.java

@@ -25,30 +25,18 @@
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
+
 import android.support.v7.app.AppCompatActivity;
 import android.support.v7.widget.Toolbar;
 import android.widget.CompoundButton;
 import android.widget.EditText;
 import android.widget.Switch;
+import android.content.Intent;
+
 
 public class MainActivity extends AppCompatActivity {
-  static final int MSG_RPC_ERROR = 0;
-  static final String MSG_RPC_ERROR_DATA_KEY = "msg_rpc_error_data_key";
-
-  private RPCProcessor tvmServerWorker;
-  @SuppressLint("HandlerLeak")
-  private final Handler rpcHandler = new Handler() {
-    @Override
-    public void dispatchMessage(Message msg) {
-      Switch switchConnect = findViewById(R.id.switch_connect);
-      if (msg.what == MSG_RPC_ERROR && switchConnect.isChecked()) {
-        // switch off and show alert dialog.
-        switchConnect.setChecked(false);
-        String msgBody = msg.getData().getString(MSG_RPC_ERROR_DATA_KEY);
-        showDialog("Error", msgBody);
-      }
-    }
-  };
+
+  private RPCWatchdog watchdog;
 
   private void showDialog(String title, String msg) {
     AlertDialog.Builder builder = new AlertDialog.Builder(this);
@@ -71,10 +59,6 @@ protected void onCreate(Bundle savedInstanceState) {
     Toolbar toolbar = findViewById(R.id.toolbar);
     setSupportActionBar(toolbar);
 
-    tvmServerWorker = new RPCProcessor(rpcHandler);
-    tvmServerWorker.setDaemon(true);
-    tvmServerWorker.start();
-
     Switch switchConnect = findViewById(R.id.switch_connect);
     switchConnect.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
       @Override
@@ -88,25 +72,33 @@ public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
         }
       }
     });
+
     enableInputView(true);
+
   }
 
   @Override
   protected void onDestroy() {
     super.onDestroy();
-    tvmServerWorker.disconnect();
+    if (watchdog != null) {
+        watchdog.disconnect();
+        watchdog = null;
+    }
   }
 
   private void connectProxy() {
     EditText edProxyAddress = findViewById(R.id.input_address);
     EditText edProxyPort = findViewById(R.id.input_port);
     EditText edAppKey = findViewById(R.id.input_key);
-
     final String proxyHost = edProxyAddress.getText().toString();
     final int proxyPort = Integer.parseInt(edProxyPort.getText().toString());
     final String key = edAppKey.getText().toString();
 
-    tvmServerWorker.connect(proxyHost, proxyPort, key);
+    System.err.println("creating watchdog thread...");
+    watchdog = new RPCWatchdog(proxyHost, proxyPort, key, this);
+
+    System.err.println("starting watchdog thread...");
+    watchdog.start();
 
     SharedPreferences pref = getApplicationContext().getSharedPreferences("RPCProxyPreference", Context.MODE_PRIVATE);
     SharedPreferences.Editor editor = pref.edit();
@@ -117,8 +109,10 @@ private void connectProxy() {
   }
 
   private void disconnect() {
-    tvmServerWorker.disconnect();
-    System.err.println("Disconnected.");
+    if (watchdog != null) {
+        watchdog.disconnect();
+        watchdog = null;
+    }
   }
 
   private void enableInputView(boolean enable) {

apps/android_rpc/app/src/main/java/ml/dmlc/tvm/tvmrpc/RPCProcessor.java

@@ -34,10 +34,11 @@ class RPCProcessor extends Thread {
   private String host;
   private int port;
   private String key;
-
   private boolean running = false;
+  private long startTime;
   private ConnectProxyServerProcessor currProcessor;
-  private final Handler uiHandler;
+  private boolean kill = false;
+  public static final int SESSION_TIMEOUT = 30000;
 
   static final SocketFileDescriptorGetter socketFdGetter
       = new SocketFileDescriptorGetter() {
@@ -46,9 +47,18 @@ public int get(Socket socket) {
           return ParcelFileDescriptor.fromSocket(socket).getFd();
         }
       };
+  // callback to initialize the start time of an rpc session
+  class setTimeCallback implements Runnable { 
+    private RPCProcessor rPCProcessor;
+
+    public setTimeCallback(RPCProcessor rPCProcessor) {
+        this.rPCProcessor = rPCProcessor;    
+    }
 
-  RPCProcessor(Handler uiHandler) {
-    this.uiHandler = uiHandler;
+    @Override
+    public void run() {
+        rPCProcessor.setStartTime();
+    }
   }
 
   @Override public void run() {
@@ -61,23 +71,51 @@ public int get(Socket socket) {
           } catch (InterruptedException e) {
           }
         }
-        currProcessor = new ConnectProxyServerProcessor(host, port, key, socketFdGetter);
-      }
-      try {
-        currProcessor.run();
-      } catch (Throwable e) {
-        disconnect();
-        // turn connect switch off.
-        Message message = new Message();
-        message.what = MainActivity.MSG_RPC_ERROR;
-        Bundle bundle = new Bundle();
-        bundle.putString(MainActivity.MSG_RPC_ERROR_DATA_KEY, e.getMessage());
-        message.setData(bundle);
-        uiHandler.sendMessage(message);
+        // if kill, we do nothing and wait for app restart
+        // to prevent race where timedOut was reported but restart has not
+        // happened yet
+        if (kill) {
+            System.err.println("waiting for restart...");
+            currProcessor = null;
+        }
+        else {
+            startTime = 0;
+            currProcessor = new ConnectProxyServerProcessor(host, port, key, socketFdGetter);
+            currProcessor.setStartTimeCallback(new setTimeCallback(this));
+        }
       }
+        if (currProcessor != null)
+            currProcessor.run();
     }
   }
 
+  /**
+   * check if the current RPCProcessor has timed out while in a session
+   */
+  synchronized boolean timedOut(long curTime) {
+    if (startTime == 0) {
+        return false;
+    }
+    else if ((curTime - startTime) > SESSION_TIMEOUT) {
+        System.err.println("set kill flag...");
+        kill = true;
+        return true;
+    }
+    return false;
+  }
+
+  /**
+   * set the start time of the current RPC session (used in callback)
+   */
+  synchronized void setStartTime() {
+    startTime = System.currentTimeMillis();
+    System.err.println("start time set to: " + startTime);
+  }
+
+  synchronized long getStartTime() {
+    return startTime;
+  }
+
   /**
    * Disconnect from the proxy server.
    */

apps/android_rpc/app/src/main/java/ml/dmlc/tvm/tvmrpc/RPCService.java

@@ -0,0 +1,64 @@
+package ml.dmlc.tvm.tvmrpc;
+
+import android.app.Service;
+import android.os.IBinder;
+import android.content.Intent;
+
+public class RPCService extends Service {
+    private String host;
+    private int port;
+    private String key;
+    private int intentNum;
+    private RPCProcessor tvmServerWorker;
+
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        synchronized(this) {
+            System.err.println("start command intent");
+            // use an alternate kill to prevent android from recycling the
+            // process
+            if (intent.getBooleanExtra("kill", false)) {
+                System.err.println("rpc service received kill...");
+                System.exit(0);
+            }
+
+            this.host = intent.getStringExtra("host");
+            this.port = intent.getIntExtra("port", 9090);
+            this.key = intent.getStringExtra("key");
+            System.err.println("got the following: " + this.host + ", " + this.port + ", " + this.key);
+            System.err.println("intent num: " + this.intentNum);
+
+            if (tvmServerWorker == null) {
+                System.err.println("service created worker...");
+                tvmServerWorker = new RPCProcessor();
+                tvmServerWorker.setDaemon(true);
+                tvmServerWorker.start();
+                tvmServerWorker.connect(this.host, this.port, this.key);
+            }
+            else if (tvmServerWorker.timedOut(System.currentTimeMillis())) {
+                System.err.println("rpc service timed out, killing self...");
+                System.exit(0);
+            }
+            this.intentNum++; 
+        }
+        // do not restart unless watchdog/app expliciltly does so
+        return START_NOT_STICKY;
+    }
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        System.err.println("rpc service got onBind, doing nothing...");
+        return null;
+    }
+
+    @Override
+    public void onCreate() {
+        System.err.println("rpc service onCreate...");
+    }
+
+    @Override
+    public void onDestroy() {
+        tvmServerWorker.disconnect();
+        System.err.println("rpc service onDestroy...");
+    }
+}

apps/android_rpc/app/src/main/java/ml/dmlc/tvm/tvmrpc/RPCWatchdog.java

@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ml.dmlc.tvm.tvmrpc;
+
+import android.content.Context;
+import android.content.Intent;
+
+/**
+ * Watchdog for RPCService
+ */
+class RPCWatchdog extends Thread {
+  public static final int WATCHDOG_POLL_INTERVAL = 5000;
+  private String host;
+  private int port;
+  private String key;
+  private Context context;
+  private boolean done = false;
+
+  public RPCWatchdog(String host, int port, String key, Context context) {
+    super();
+    this.host = host;
+    this.port = port;
+    this.key = key;
+    this.context = context;
+  }
+
+  /**
+   * Polling loop to check on RPCService status
+   */ 
+  @Override public void run() {
+    try {
+        while (true) {
+          synchronized (this) {
+              if (done) {
+                System.err.println("watchdog done, returning...");
+                return;
+              }
+              else {
+                System.err.println("polling rpc service...");                                  
+                System.err.println("sending rpc service intent...");
+                Intent intent = new Intent(context, RPCService.class);
+                intent.putExtra("host", host);
+                intent.putExtra("port", port);
+                intent.putExtra("key", key);
+                // will implicilty restart the service if it died
+                context.startService(intent);
+              }
+          }
+          Thread.sleep(WATCHDOG_POLL_INTERVAL);
+        }
+    } catch (InterruptedException e) {
+    }
+  }
+
+  /**
+   * Disconnect from the proxy server.
+   */
+  synchronized void disconnect() {
+    // kill service
+    System.err.println("watchdog disconnect call...");
+    System.err.println("stopping rpc service...");
+    done = true;
+    Intent intent = new Intent(context, RPCService.class);
+    intent.putExtra("kill", true); 
+    context.startService(intent); 
+  }
+}