Tell system to reinitialize when it refuses to give us data we need

Another hacky workaround to fix a hacky workaround.

We had talked to Google about the backup API not getting notified when essential K/V apps like @pm@ don't have new data for backup. The only option they offered is BackupMonitor which gets the information at least, but out of process on another thread.

 So we implemented a hacky workaround where BackupMonitor tells SnapshotCreator to extract backup data from an old snapshot.

 Unfortunately, it is possible that we do a backup run which includes @pm@, but encounters an error later, so the system cancels the entire backup which causes us not to have @pm@ data in a snapshots for re-use. Still, the system thinks we backed up @pm@ and doesn't give us its data.

Author: grote

app/src/main/java/com/stevesoltys/seedvault/repo/RepoModule.kt

@@ -19,7 +19,7 @@ val repoModule = module {
         val snapshotFolder = File(androidContext().filesDir, FOLDER_SNAPSHOTS)
         SnapshotManager(snapshotFolder, get(), get(), get())
     }
-    factory { SnapshotCreatorFactory(androidContext(), get(), get(), get()) }
+    factory { SnapshotCreatorFactory(androidContext(), get(), get(), get(), get()) }
     factory { Pruner(get(), get(), get(), get()) }
     single { Checker(get(), get(), get(), get(), get(), get()) }
 }

app/src/main/java/com/stevesoltys/seedvault/repo/SnapshotCreator.kt

@@ -25,6 +25,7 @@ import com.stevesoltys.seedvault.proto.Snapshot
 import com.stevesoltys.seedvault.proto.Snapshot.Apk
 import com.stevesoltys.seedvault.proto.Snapshot.App
 import com.stevesoltys.seedvault.proto.Snapshot.Blob
+import com.stevesoltys.seedvault.transport.backup.BackupInitializer
 import com.stevesoltys.seedvault.transport.backup.PackageService
 import com.stevesoltys.seedvault.transport.backup.isSystemApp
 import io.github.oshai.kotlinlogging.KotlinLogging
@@ -41,6 +42,7 @@ internal class SnapshotCreator(
     private val clock: Clock,
     private val packageService: PackageService,
     private val metadataManager: MetadataManager,
+    private val backupInitializer: BackupInitializer,
 ) {
 
     private val log = KotlinLogging.logger { }
@@ -115,44 +117,55 @@ internal class SnapshotCreator(
      * we try to extract data from the given [snapshot] (ideally we latest we have) and
      * add it to the current snapshot under construction.
      *
-     * @param warnNoData log a warning, if [snapshot] had no data for the given [packageName].
+     * @param isStopped set to true if the app had no data, because it is currently force-stopped.
      */
-    fun onNoDataInCurrentRun(snapshot: Snapshot, packageName: String, isStopped: Boolean = false) {
-        log.info { "onKvPackageNotChanged(${snapshot.token}, $packageName)" }
+    fun onNoDataInCurrentRun(snapshot: Snapshot?, packageName: String, isStopped: Boolean = false) {
+        log.info { "onKvPackageNotChanged(${snapshot?.token}, $packageName)" }
 
         if (appBuilderMap.containsKey(packageName)) {
             // the system backs up K/V apps repeatedly, e.g. @pm@
             log.info { "  Already have data for $packageName in current snapshot, not touching it" }
             return
         }
-        val app = snapshot.appsMap[packageName]
-        if (app == null) {
-            if (!isStopped) log.error {
-                "  No changed data for $packageName, but we had no data for it"
+        if (snapshot == null) {
+            log.error { "No latest snapshot! Initializing transport..." }
+            // Tell the system that it needs to initialize our transport,
+            // so it stops telling us that it has no data.
+            // It seems crazy that we can do this mid-backup
+            val error = { log.error { "Error initializing transport." } }
+            backupInitializer.initialize(error) {
+                log.info { "Success initializing transport." }
+            }
+        } else {
+            val app = snapshot.appsMap[packageName]
+            if (app == null) {
+                if (!isStopped) log.error {
+                    "  No changed data for $packageName, but we had no data for it"
+                }
+                return
             }
-            return
-        }
 
-        // get chunkIds from last snapshot
-        val chunkIds = app.chunkIdsList.hexFromProto() +
-            app.apk.splitsList.flatMap { it.chunkIdsList }.hexFromProto()
+            // get chunkIds from last snapshot
+            val chunkIds = app.chunkIdsList.hexFromProto() +
+                app.apk.splitsList.flatMap { it.chunkIdsList }.hexFromProto()
 
-        // get blobs for chunkIds
-        val blobMap = mutableMapOf<String, Blob>()
-        chunkIds.forEach { chunkId ->
-            val blob = snapshot.blobsMap[chunkId]
-            if (blob == null) log.error { "  No blob for $packageName chunk $chunkId" }
-            else blobMap[chunkId] = blob
-        }
+            // get blobs for chunkIds
+            val blobMap = mutableMapOf<String, Blob>()
+            chunkIds.forEach { chunkId ->
+                val blob = snapshot.blobsMap[chunkId]
+                if (blob == null) log.error { "  No blob for $packageName chunk $chunkId" }
+                else blobMap[chunkId] = blob
+            }
 
-        // add info to current snapshot
-        appBuilderMap[packageName] = app.toBuilder()
-        blobsMap.putAll(blobMap)
+            // add info to current snapshot
+            appBuilderMap[packageName] = app.toBuilder()
+            blobsMap.putAll(blobMap)
 
-        // record local metadata if this is not a stopped app
-        if (!isStopped) {
-            val packageInfo = PackageInfo().apply { this.packageName = packageName }
-            metadataManager.onPackageBackedUp(packageInfo, app.type.toBackupType(), app.size)
+            // record local metadata if this is not a stopped app
+            if (!isStopped) {
+                val packageInfo = PackageInfo().apply { this.packageName = packageName }
+                metadataManager.onPackageBackedUp(packageInfo, app.type.toBackupType(), app.size)
+            }
         }
     }
 

app/src/main/java/com/stevesoltys/seedvault/repo/SnapshotCreatorFactory.kt

@@ -8,6 +8,7 @@ package com.stevesoltys.seedvault.repo
 import android.content.Context
 import com.stevesoltys.seedvault.Clock
 import com.stevesoltys.seedvault.metadata.MetadataManager
+import com.stevesoltys.seedvault.transport.backup.BackupInitializer
 import com.stevesoltys.seedvault.transport.backup.PackageService
 
 /**
@@ -18,7 +19,8 @@ internal class SnapshotCreatorFactory(
     private val clock: Clock,
     private val packageService: PackageService,
     private val metadataManager: MetadataManager,
+    private val backupInitializer: BackupInitializer,
 ) {
     fun createSnapshotCreator() =
-        SnapshotCreator(context, clock, packageService, metadataManager)
+        SnapshotCreator(context, clock, packageService, metadataManager, backupInitializer)
 }

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt

@@ -75,7 +75,7 @@ internal class BackupCoordinator(
     private val state = CoordinatorState(
         calledInitialize = false,
         calledClearBackupData = false,
-        cancelReason = UNKNOWN_ERROR
+        cancelReason = UNKNOWN_ERROR,
     )
     private val launchableSystemApps by lazy {
         packageService.launchableSystemApps.map { it.activityInfo.packageName }.toSet()

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupTransportMonitor.kt

@@ -33,11 +33,7 @@ internal class BackupTransportMonitor(
         log.info { "sendNoDataChanged($packageName)" }
 
         val snapshot = snapshotManager.latestSnapshot
-        if (snapshot == null) {
-            log.error { "No latest snapshot!" }
-        } else {
-            val snapshotCreator = appBackupManager.snapshotCreator ?: error("No SnapshotCreator")
-            snapshotCreator.onNoDataInCurrentRun(snapshot, packageName)
-        }
+        val snapshotCreator = appBackupManager.snapshotCreator ?: error("No SnapshotCreator")
+        snapshotCreator.onNoDataInCurrentRun(snapshot, packageName)
     }
 }

app/src/test/java/com/stevesoltys/seedvault/repo/SnapshotCreatorTest.kt

@@ -23,12 +23,14 @@ import com.stevesoltys.seedvault.proto.SnapshotKt.app
 import com.stevesoltys.seedvault.proto.SnapshotKt.split
 import com.stevesoltys.seedvault.proto.copy
 import com.stevesoltys.seedvault.transport.TransportTest
+import com.stevesoltys.seedvault.transport.backup.BackupInitializer
 import com.stevesoltys.seedvault.transport.backup.PackageService
 import com.stevesoltys.seedvault.worker.BASE_SPLIT
 import io.mockk.Runs
 import io.mockk.every
 import io.mockk.just
 import io.mockk.mockk
+import io.mockk.verify
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertTrue
 import org.junit.Test
@@ -46,7 +48,9 @@ internal class SnapshotCreatorTest : TransportTest() {
 
     private val ctx: Context = ApplicationProvider.getApplicationContext()
     private val packageService: PackageService = mockk()
-    private val snapshotCreator = SnapshotCreator(ctx, clock, packageService, metadataManager)
+    private val backupInitializer: BackupInitializer = mockk()
+    private val snapshotCreator =
+        SnapshotCreator(ctx, clock, packageService, metadataManager, backupInitializer)
 
     init {
         every { packageService.launchableSystemApps } returns emptyList()
@@ -173,6 +177,15 @@ internal class SnapshotCreatorTest : TransportTest() {
         }
     }
 
+    @Test
+    fun `test onNoDataInCurrentRun re-initializes if no snapshot available`() {
+        every { backupInitializer.initialize(any(), any()) } just Runs
+
+        snapshotCreator.onNoDataInCurrentRun(null, MAGIC_PACKAGE_MANAGER)
+
+        verify { backupInitializer.initialize(any(), any()) }
+    }
+
     @Test
     fun `test onNoDataInCurrentRun`() {
         val snapshot = snapshot.copy {

app/src/test/java/com/stevesoltys/seedvault/transport/backup/BackupCreationTest.kt

@@ -66,8 +66,13 @@ internal class BackupCreationTest : BackupTest() {
     private val backupReceiver = BackupReceiver(blobCache, blobCreator, cryptoImpl)
     private val appBackupManager = mockk<AppBackupManager>()
     private val packageService = mockk<PackageService>()
-    private val snapshotCreator =
-        SnapshotCreator(context, clock, packageService, mockk(relaxed = true))
+    private val snapshotCreator = SnapshotCreator(
+        context = context,
+        clock = clock,
+        packageService = packageService,
+        metadataManager = mockk(relaxed = true),
+        backupInitializer = mockk(relaxed = true),
+    )
     private val notificationManager = mockk<BackupNotificationManager>()
     private val db = TestKvDbManager()