creating a dedicated threadsafe Session instance initializer in order to attempt to restore session when they're not yet created in memory

vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt

@@ -16,8 +16,10 @@
 
 package im.vector.app.core.di
 
+import android.content.Context
 import arrow.core.Option
 import im.vector.app.ActiveSessionDataSource
+import im.vector.app.core.extensions.configureAndStart
 import im.vector.app.core.pushers.UnifiedPushHelper
 import im.vector.app.core.services.GuardServiceStarter
 import im.vector.app.features.call.webrtc.WebRtcCallManager
@@ -25,6 +27,12 @@ import im.vector.app.features.crypto.keysrequest.KeyRequestHandler
 import im.vector.app.features.crypto.verification.IncomingVerificationRequestHandler
 import im.vector.app.features.notifications.PushRuleTriggerListener
 import im.vector.app.features.session.SessionListener
+import kotlinx.coroutines.DelicateCoroutinesApi
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.newSingleThreadContext
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
+import org.matrix.android.sdk.api.auth.AuthenticationService
 import org.matrix.android.sdk.api.session.Session
 import timber.log.Timber
 import java.util.concurrent.atomic.AtomicReference
@@ -41,7 +49,10 @@ class ActiveSessionHolder @Inject constructor(
         private val sessionListener: SessionListener,
         private val imageManager: ImageManager,
         private val unifiedPushHelper: UnifiedPushHelper,
-        private val guardServiceStarter: GuardServiceStarter
+        private val guardServiceStarter: GuardServiceStarter,
+        private val sessionInitializer: SessionInitializer,
+        private val applicationContext: Context,
+        private val authenticationService: AuthenticationService,
 ) {
 
     private var activeSessionReference: AtomicReference<Session?> = AtomicReference()
@@ -80,18 +91,29 @@ class ActiveSessionHolder @Inject constructor(
     }
 
     fun hasActiveSession(): Boolean {
-        return activeSessionReference.get() != null
+        return activeSessionReference.get() != null || authenticationService.hasAuthenticatedSessions()
     }
 
     fun getSafeActiveSession(): Session? {
-        return activeSessionReference.get()
+        return runBlocking { getOrInitializeSession(startSync = true) }
     }
 
     fun getActiveSession(): Session {
-        return activeSessionReference.get()
+        return getSafeActiveSession()
                 ?: throw IllegalStateException("You should authenticate before using this")
     }
 
+    suspend fun getOrInitializeSession(startSync: Boolean): Session? {
+        return activeSessionReference.get() ?: sessionInitializer.tryInitialize(readCurrentSession = { activeSessionReference.get() }) { session ->
+            setActiveSession(session)
+            withContext(Dispatchers.Main) {
+                session.configureAndStart(applicationContext, startSyncing = startSync)
+            }
+        }
+    }
+
+    fun isWaitingForSessionInitialization() = activeSessionReference.get() == null && authenticationService.hasAuthenticatedSessions()
+
     // TODO Stop sync ?
 //    fun switchToSession(sessionParams: SessionParams) {
 //        val newActiveSession = authenticationService.getSession(sessionParams)

vector/src/main/java/im/vector/app/core/di/ActiveSessionSetter.kt

@@ -1,40 +0,0 @@
-/*
- * Copyright 2022 New Vector Ltd
- *
- * Licensed 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 im.vector.app.core.di
-
-import android.content.Context
-import im.vector.app.core.extensions.configureAndStart
-import org.matrix.android.sdk.api.auth.AuthenticationService
-import javax.inject.Inject
-
-class ActiveSessionSetter @Inject constructor(
-        private val activeSessionHolder: ActiveSessionHolder,
-        private val authenticationService: AuthenticationService,
-        private val applicationContext: Context,
-) {
-    fun shouldSetActionSession(): Boolean {
-        return authenticationService.hasAuthenticatedSessions() && !activeSessionHolder.hasActiveSession()
-    }
-
-    fun tryToSetActiveSession(startSync: Boolean) {
-        if (shouldSetActionSession()) {
-            val lastAuthenticatedSession = authenticationService.getLastAuthenticatedSession()!!
-            activeSessionHolder.setActiveSession(lastAuthenticatedSession)
-            lastAuthenticatedSession.configureAndStart(applicationContext, startSyncing = startSync)
-        }
-    }
-}

vector/src/main/java/im/vector/app/core/di/SessionInitializer.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2022 New Vector Ltd
+ *
+ * Licensed 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 im.vector.app.core.di
+
+import kotlinx.coroutines.DelicateCoroutinesApi
+import kotlinx.coroutines.newSingleThreadContext
+import kotlinx.coroutines.withContext
+import org.matrix.android.sdk.api.auth.AuthenticationService
+import org.matrix.android.sdk.api.session.Session
+import javax.inject.Inject
+
+@OptIn(DelicateCoroutinesApi::class)
+private val INITIALIZER_CONTEXT = newSingleThreadContext("session-initializer")
+
+class SessionInitializer @Inject constructor(
+        private val authenticationService: AuthenticationService,
+) {
+
+    /**
+     * A thread safe way to initialize the last authenticated Session instance.
+     *
+     * @param readCurrentSession expects an in-memory Session to be provided or null if not yet set.
+     * @param initializer callback to allow additional initialization on the Session, such as setting the in-memory Session instance.
+     * @return the initialized Session or null when no authenticated sessions are available.
+     */
+    suspend fun tryInitialize(readCurrentSession: () -> Session?, initializer: suspend (Session) -> Unit): Session? {
+        return withContext(INITIALIZER_CONTEXT) {
+            val currentInMemorySession = readCurrentSession()
+            when {
+                currentInMemorySession != null -> currentInMemorySession
+                authenticationService.hasAuthenticatedSessions() -> {
+                    val lastAuthenticatedSession = authenticationService.getLastAuthenticatedSession()!!
+                    lastAuthenticatedSession.also { initializer(lastAuthenticatedSession) }
+                }
+                else -> null
+            }
+        }
+    }
+}

vector/src/main/java/im/vector/app/core/pushers/VectorMessagingReceiver.kt

@@ -27,7 +27,6 @@ import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import dagger.hilt.android.AndroidEntryPoint
 import im.vector.app.BuildConfig
 import im.vector.app.core.di.ActiveSessionHolder
-import im.vector.app.core.di.ActiveSessionSetter
 import im.vector.app.core.network.WifiDetector
 import im.vector.app.core.pushers.model.PushData
 import im.vector.app.core.services.GuardServiceStarter
@@ -38,6 +37,7 @@ import im.vector.app.features.settings.BackgroundSyncMode
 import im.vector.app.features.settings.VectorDataStore
 import im.vector.app.features.settings.VectorPreferences
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
@@ -60,7 +60,6 @@ class VectorMessagingReceiver : MessagingReceiver() {
     @Inject lateinit var notificationDrawerManager: NotificationDrawerManager
     @Inject lateinit var notifiableEventResolver: NotifiableEventResolver
     @Inject lateinit var pushersManager: PushersManager
-    @Inject lateinit var activeSessionSetter: ActiveSessionSetter
     @Inject lateinit var activeSessionHolder: ActiveSessionHolder
     @Inject lateinit var vectorPreferences: VectorPreferences
     @Inject lateinit var vectorDataStore: VectorDataStore
@@ -116,7 +115,7 @@ class VectorMessagingReceiver : MessagingReceiver() {
                 // we are in foreground, let the sync do the things?
                 Timber.tag(loggerTag.value).d("PUSH received in a foreground state, ignore")
             } else {
-                onMessageReceivedInternal(pushData)
+                coroutineScope.launch(Dispatchers.IO) { onMessageReceivedInternal(pushData) }
             }
         }
     }
@@ -170,7 +169,7 @@ class VectorMessagingReceiver : MessagingReceiver() {
      *
      * @param pushData Object containing message data.
      */
-    private fun onMessageReceivedInternal(pushData: PushData) {
+    private suspend fun onMessageReceivedInternal(pushData: PushData) {
         try {
             if (BuildConfig.LOW_PRIVACY_LOG_ENABLE) {
                 Timber.tag(loggerTag.value).d("## onMessageReceivedInternal() : $pushData")
@@ -178,12 +177,7 @@ class VectorMessagingReceiver : MessagingReceiver() {
                 Timber.tag(loggerTag.value).d("## onMessageReceivedInternal()")
             }
 
-            val session = activeSessionHolder.getSafeActiveSession()
-                    ?: run {
-                        // Active session may not exist yet, if MainActivity has not been launched
-                        activeSessionSetter.tryToSetActiveSession(startSync = false)
-                        activeSessionHolder.getSafeActiveSession()
-                    }
+            val session = activeSessionHolder.getOrInitializeSession(startSync = false)
 
             if (session == null) {
                 Timber.tag(loggerTag.value).w("## Can't sync from push, no current session")

vector/src/main/java/im/vector/app/features/start/StartAppViewModel.kt

@@ -20,7 +20,7 @@ import com.airbnb.mvrx.MavericksViewModelFactory
 import dagger.assisted.Assisted
 import dagger.assisted.AssistedFactory
 import dagger.assisted.AssistedInject
-import im.vector.app.core.di.ActiveSessionSetter
+import im.vector.app.core.di.ActiveSessionHolder
 import im.vector.app.core.di.MavericksAssistedViewModelFactory
 import im.vector.app.core.di.hiltMavericksViewModelFactory
 import im.vector.app.core.platform.VectorViewModel
@@ -31,7 +31,7 @@ import kotlin.time.Duration.Companion.seconds
 
 class StartAppViewModel @AssistedInject constructor(
         @Assisted val initialState: StartAppViewState,
-        private val activeSessionSetter: ActiveSessionSetter,
+        private val sessionHolder: ActiveSessionHolder,
 ) : VectorViewModel<StartAppViewState, StartAppAction, StartAppViewEvent>(initialState) {
 
     @AssistedFactory
@@ -42,7 +42,7 @@ class StartAppViewModel @AssistedInject constructor(
     companion object : MavericksViewModelFactory<StartAppViewModel, StartAppViewState> by hiltMavericksViewModelFactory()
 
     fun shouldStartApp(): Boolean {
-        return activeSessionSetter.shouldSetActionSession()
+        return sessionHolder.isWaitingForSessionInitialization()
     }
 
     override fun handle(action: StartAppAction) {
@@ -55,11 +55,15 @@ class StartAppViewModel @AssistedInject constructor(
         handleLongProcessing()
         viewModelScope.launch(Dispatchers.IO) {
             // This can take time because of DB migration(s), so do it in a background task.
-            activeSessionSetter.tryToSetActiveSession(startSync = true)
+            eagerlyInitializeSession()
             _viewEvents.post(StartAppViewEvent.AppStarted)
         }
     }
 
+    private suspend fun eagerlyInitializeSession() {
+        sessionHolder.getOrInitializeSession(startSync = true)
+    }
+
     private fun handleLongProcessing() {
         viewModelScope.launch(Dispatchers.Default) {
             delay(1.seconds.inWholeMilliseconds)