Make RestoreSession.getAvailableRestoreSets() asynchronous

This transaction can involve the transport having to query a remote backend
over the wire, so it can take a Long Time(tm).  Make it main-thread-safe by
making it asynchronous, with the results passed as a callback to the invoker's
RestoreObserver.  We also make the IRestoreObserver callback interface
properly oneway.

Bug #2550665
Bug #2549422

Change-Id: If18a233a0a3d54c7b55101715c9e6195b762c5a0

7 files changed, 181 insertions, 35 deletions

diff --git a/api/current.xml b/api/current.xml
index cf4686765d0..b0d99317284 100644
--- a/api/current.xml
+++ b/api/current.xml
@@ -27381,6 +27381,47 @@
  visibility="public"
 >
 </constructor>
+<method name="onUpdate"
+ return="void"
+ abstract="false"
+ native="false"
+ synchronized="false"
+ static="false"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<parameter name="nowBeingRestored" type="int">
+</parameter>
+<parameter name="currentPackage" type="java.lang.String">
+</parameter>
+</method>
+<method name="restoreFinished"
+ return="void"
+ abstract="false"
+ native="false"
+ synchronized="false"
+ static="false"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<parameter name="error" type="int">
+</parameter>
+</method>
+<method name="restoreStarting"
+ return="void"
+ abstract="false"
+ native="false"
+ synchronized="false"
+ static="false"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<parameter name="numPackages" type="int">
+</parameter>
+</method>
 </class>
 <class name="SharedPreferencesBackupHelper"
  extends="android.app.backup.FileBackupHelperBase"
diff --git a/cmds/bmgr/src/com/android/commands/bmgr/Bmgr.java b/cmds/bmgr/src/com/android/commands/bmgr/Bmgr.java
index fa8a7c8c478..5612158021d 100644
--- a/cmds/bmgr/src/com/android/commands/bmgr/Bmgr.java
+++ b/cmds/bmgr/src/com/android/commands/bmgr/Bmgr.java
@@ -254,11 +254,13 @@ public final class Bmgr {
 
     private void doListRestoreSets() {
         try {
-            RestoreSet[] sets = mRestore.getAvailableRestoreSets();
-            if (sets == null || sets.length == 0) {
-                System.out.println("No restore sets available");
+            RestoreObserver observer = new RestoreObserver();
+            int err = mRestore.getAvailableRestoreSets(observer);
+            if (err != 0) {
+                System.out.println("Unable to request restore sets");
             } else {
-                printRestoreSets(sets);
+                observer.waitForCompletion();
+                printRestoreSets(observer.sets);
             }
         } catch (RemoteException e) {
             System.err.println(e.toString());
@@ -274,6 +276,16 @@ public final class Bmgr {
 
     class RestoreObserver extends IRestoreObserver.Stub {
         boolean done;
+        RestoreSet[] sets = null;
+
+        public void restoreSetsAvailable(RestoreSet[] result) {
+            synchronized (this) {
+                sets = result;
+                done = true;
+                this.notify();
+            }
+        }
+
         public void restoreStarting(int numPackages) {
             System.out.println("restoreStarting: " + numPackages + " packages");
         }
@@ -359,8 +371,11 @@ public final class Bmgr {
                 System.err.println(BMGR_NOT_RUNNING_ERR);
                 return;
             }
-            RestoreSet[] sets = mRestore.getAvailableRestoreSets();
-            if (sets != null) {
+            RestoreSet[] sets = null;
+            int err = mRestore.getAvailableRestoreSets(observer);
+            if (err != 0) {
+                observer.waitForCompletion();
+                sets = observer.sets;
                 for (RestoreSet s : sets) {
                     if (s.token == token) {
                         System.out.println("Scheduling restore: " + s.name);
diff --git a/core/java/android/app/backup/IRestoreObserver.aidl b/core/java/android/app/backup/IRestoreObserver.aidl
index ec856839cb3..449765ec475 100644
--- a/core/java/android/app/backup/IRestoreObserver.aidl
+++ b/core/java/android/app/backup/IRestoreObserver.aidl
@@ -16,12 +16,26 @@
 
 package android.app.backup;
 
+import android.app.backup.RestoreSet;
+
 /**
  * Callback class for receiving progress reports during a restore operation.
  *
  * @hide
  */
-interface IRestoreObserver {
+oneway interface IRestoreObserver {
+    /**
+     * Supply a list of the restore datasets available from the current transport.  This
+     * method is invoked as a callback following the application's use of the
+     * {@link android.app.backup.IRestoreSession.getAvailableRestoreSets} method.
+     *
+     * @param result An array of {@link android.app.backup.RestoreSet RestoreSet} objects
+     *   describing all of the available datasets that are candidates for restoring to
+     *   the current device.  If no applicable datasets exist, {@code result} will be
+     *   {@code null}.
+     */
+    void restoreSetsAvailable(in RestoreSet[] result);
+
     /**
      * The restore operation has begun.
      *
@@ -32,8 +46,8 @@ interface IRestoreObserver {
 
     /**
      * An indication of which package is being restored currently, out of the
-     * total number provided in the restoreStarting() callback.  This method
-     * is not guaranteed to be called.
+     * total number provided in the {@link #restoreStarting(int numPackages)} callback.
+     * This method is not guaranteed to be called.
      *
      * @param nowBeingRestored The index, between 1 and the numPackages parameter
      *   to the restoreStarting() callback, of the package now being restored.
diff --git a/core/java/android/app/backup/IRestoreSession.aidl b/core/java/android/app/backup/IRestoreSession.aidl
index 58c21fea40a..1dddbb02c8b 100644
--- a/core/java/android/app/backup/IRestoreSession.aidl
+++ b/core/java/android/app/backup/IRestoreSession.aidl
@@ -29,12 +29,12 @@ interface IRestoreSession {
     /**
      * Ask the current transport what the available restore sets are.
      *
-     * @return A bundle containing two elements:  an int array under the key
-     *   "tokens" whose entries are a transport-private identifier for each backup set;
-     *   and a String array under the key "names" whose entries are the user-meaningful
-     *   text corresponding to the backup sets at each index in the tokens array.
+     * @param observer This binder points to an object whose onRestoreSetsAvailable()
+     *   method will be called to supply the results of the transport's lookup.
+     * @return Zero on success; nonzero on error.  The observer will only receive a
+     *   result callback if this method returned zero.
      */
-    RestoreSet[] getAvailableRestoreSets();
+    int getAvailableRestoreSets(IRestoreObserver observer);
 
     /**
      * Restore the given set onto the device, replacing the current data of any app
diff --git a/core/java/android/app/backup/RestoreObserver.java b/core/java/android/app/backup/RestoreObserver.java
index 0a4ea176d10..dbddb788cc7 100644
--- a/core/java/android/app/backup/RestoreObserver.java
+++ b/core/java/android/app/backup/RestoreObserver.java
@@ -17,6 +17,7 @@
 package android.app.backup;
 
 import java.lang.String;
+import android.app.backup.RestoreSet;
 
 /**
  * Callback class for receiving progress reports during a restore operation.  These
@@ -24,12 +25,27 @@ import java.lang.String;
  */
 public abstract class RestoreObserver {
     /**
+     * Supply a list of the restore datasets available from the current transport.  This
+     * method is invoked as a callback following the application's use of the
+     * {@link android.app.backup.IRestoreSession.getAvailableRestoreSets} method.
+     *
+     * @param result An array of {@link android.app.backup.RestoreSet RestoreSet} objects
+     *   describing all of the available datasets that are candidates for restoring to
+     *   the current device.  If no applicable datasets exist, {@code result} will be
+     *   {@code null}.
+     *
+     * @hide
+     */
+    public void restoreSetsAvailable(RestoreSet[] result) {
+    }
+
+    /**
      * The restore operation has begun.
      *
      * @param numPackages The total number of packages being processed in
      *   this restore operation.
      */
-    void restoreStarting(int numPackages) {
+    public void restoreStarting(int numPackages) {
     }
 
     /**
@@ -45,7 +61,7 @@ public abstract class RestoreObserver {
      *   indication of the backup manager's progress through the overall restore process.
      * @param currentPackage The name of the package now being restored.
      */
-    void onUpdate(int nowBeingRestored, String currentPackage) {
+    public void onUpdate(int nowBeingRestored, String currentPackage) {
     }
 
     /**
@@ -55,6 +71,6 @@ public abstract class RestoreObserver {
      * @param error Zero on success; a nonzero error code if the restore operation
      *   as a whole failed.
      */
-    void restoreFinished(int error) {
+    public void restoreFinished(int error) {
     }
 }
diff --git a/core/java/android/app/backup/RestoreSession.java b/core/java/android/app/backup/RestoreSession.java
index da2778b6135..24ddb99725e 100644
--- a/core/java/android/app/backup/RestoreSession.java
+++ b/core/java/android/app/backup/RestoreSession.java
@@ -40,19 +40,22 @@ public class RestoreSession {
     /**
      * Ask the current transport what the available restore sets are.
      *
-     * @return A bundle containing two elements:  an int array under the key
-     *   "tokens" whose entries are a transport-private identifier for each backup set;
-     *   and a String array under the key "names" whose entries are the user-meaningful
-     *   text corresponding to the backup sets at each index in the tokens array.
-     *   On error, returns null.
+     * @param observer a RestoreObserver object whose restoreSetsAvailable() method will
+     *   be called on the application's main thread in order to supply the results of
+     *   the restore set lookup by the backup transport.  This parameter must not be
+     *   null.
+     * @return Zero on success, nonzero on error.  The observer's restoreSetsAvailable()
+     *   method will only be called if this method returned zero.
      */
-    public RestoreSet[] getAvailableRestoreSets() {
+    public int getAvailableRestoreSets(RestoreObserver observer) {
+        int err = -1;
+        RestoreObserverWrapper obsWrapper = new RestoreObserverWrapper(mContext, observer);
         try {
-            return mBinder.getAvailableRestoreSets();
+            err = mBinder.getAvailableRestoreSets(obsWrapper);
         } catch (RemoteException e) {
             Log.d(TAG, "Can't contact server to get available sets");
-            return null;
         }
+        return err;
     }
 
     /**
@@ -151,6 +154,7 @@ public class RestoreSession {
         static final int MSG_RESTORE_STARTING = 1;
         static final int MSG_UPDATE = 2;
         static final int MSG_RESTORE_FINISHED = 3;
+        static final int MSG_RESTORE_SETS_AVAILABLE = 4;
 
         RestoreObserverWrapper(Context context, RestoreObserver appObserver) {
             mHandler = new Handler(context.getMainLooper()) {
@@ -166,6 +170,9 @@ public class RestoreSession {
                     case MSG_RESTORE_FINISHED:
                         mAppObserver.restoreFinished(msg.arg1);
                         break;
+                    case MSG_RESTORE_SETS_AVAILABLE:
+                        mAppObserver.restoreSetsAvailable((RestoreSet[])msg.obj);
+                        break;
                     }
                 }
             };
@@ -173,6 +180,11 @@ public class RestoreSession {
         }
 
         // Binder calls into this object just enqueue on the main-thread handler
+        public void restoreSetsAvailable(RestoreSet[] result) {
+            mHandler.sendMessage(
+                    mHandler.obtainMessage(MSG_RESTORE_SETS_AVAILABLE, result));
+        }
+
         public void restoreStarting(int numPackages) {
             mHandler.sendMessage(
                     mHandler.obtainMessage(MSG_RESTORE_STARTING, numPackages, 0));
diff --git a/services/java/com/android/server/BackupManagerService.java b/services/java/com/android/server/BackupManagerService.java
index 6c1fa60298f..ecf1a1d1cd7 100644
--- a/services/java/com/android/server/BackupManagerService.java
+++ b/services/java/com/android/server/BackupManagerService.java
@@ -104,7 +104,8 @@ class BackupManagerService extends IBackupManager.Stub {
     private static final int MSG_RUN_RESTORE = 3;
     private static final int MSG_RUN_CLEAR = 4;
     private static final int MSG_RUN_INITIALIZE = 5;
-    private static final int MSG_TIMEOUT = 6;
+    private static final int MSG_RUN_GET_RESTORE_SETS = 6;
+    private static final int MSG_TIMEOUT = 7;
 
     // Timeout interval for deciding that a bind or clear-data has taken too long
     static final long TIMEOUT_INTERVAL = 10 * 1000;
@@ -177,6 +178,19 @@ class BackupManagerService extends IBackupManager.Stub {
     IBackupTransport mLocalTransport, mGoogleTransport;
     ActiveRestoreSession mActiveRestoreSession;
 
+    class RestoreGetSetsParams {
+        public IBackupTransport transport;
+        public ActiveRestoreSession session;
+        public IRestoreObserver observer;
+
+        RestoreGetSetsParams(IBackupTransport _transport, ActiveRestoreSession _session,
+                IRestoreObserver _observer) {
+            transport = _transport;
+            session = _session;
+            observer = _observer;
+        }
+    }
+
     class RestoreParams {
         public IBackupTransport transport;
         public IRestoreObserver observer;
@@ -333,6 +347,36 @@ class BackupManagerService extends IBackupManager.Stub {
                 break;
             }
 
+            case MSG_RUN_GET_RESTORE_SETS:
+            {
+                // Like other async operations, this is entered with the wakelock held
+                RestoreSet[] sets = null;
+                RestoreGetSetsParams params = (RestoreGetSetsParams)msg.obj;
+                try {
+                    sets = params.transport.getAvailableRestoreSets();
+                    // cache the result in the active session
+                    synchronized (params.session) {
+                        params.session.mRestoreSets = sets;
+                    }
+                    if (sets == null) EventLog.writeEvent(EventLogTags.RESTORE_TRANSPORT_FAILURE);
+                } catch (Exception e) {
+                    Slog.e(TAG, "Error from transport getting set list");
+                } finally {
+                    if (params.observer != null) {
+                        try {
+                            params.observer.restoreSetsAvailable(sets);
+                        } catch (RemoteException re) {
+                            Slog.e(TAG, "Unable to report listing to observer");
+                        } catch (Exception e) {
+                            Slog.e(TAG, "Restore observer threw", e);
+                        }
+                    }
+
+                    mWakelock.release();
+                }
+                break;
+            }
+
             case MSG_TIMEOUT:
             {
                 synchronized (mCurrentOpLock) {
@@ -2343,24 +2387,28 @@ class BackupManagerService extends IBackupManager.Stub {
         }
 
         // --- Binder interface ---
-        public synchronized RestoreSet[] getAvailableRestoreSets() {
+        public synchronized int getAvailableRestoreSets(IRestoreObserver observer) {
             mContext.enforceCallingOrSelfPermission(android.Manifest.permission.BACKUP,
                     "getAvailableRestoreSets");
+            if (observer == null) {
+                throw new IllegalArgumentException("Observer must not be null");
+            }
 
             long oldId = Binder.clearCallingIdentity();
             try {
                 if (mRestoreTransport == null) {
                     Slog.w(TAG, "Null transport getting restore sets");
-                    return null;
-                }
-                if (mRestoreSets == null) { // valid transport; do the one-time fetch
-                    mRestoreSets = mRestoreTransport.getAvailableRestoreSets();
-                    if (mRestoreSets == null) EventLog.writeEvent(EventLogTags.RESTORE_TRANSPORT_FAILURE);
-                }
-                return mRestoreSets;
+                    return -1;
+                }
+                // spin off the transport request to our service thread
+                mWakelock.acquire();
+                Message msg = mBackupHandler.obtainMessage(MSG_RUN_GET_RESTORE_SETS,
+                        new RestoreGetSetsParams(mRestoreTransport, this, observer));
+                mBackupHandler.sendMessage(msg);
+                return 0;
             } catch (Exception e) {
                 Slog.e(TAG, "Error in getAvailableRestoreSets", e);
-                return null;
+                return -1;
             } finally {
                 Binder.restoreCallingIdentity(oldId);
             }