When a background SDK task fails, react in the client (#6166)

- For initialization issues or errors, we just print and report them.
- For panics (unrecoverable errors) we also crash the app.

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustClientSessionDelegate.kt

@@ -10,11 +10,14 @@ package io.element.android.libraries.matrix.impl
 
 import io.element.android.libraries.core.coroutine.CoroutineDispatchers
 import io.element.android.libraries.core.log.logger.LoggerTag
+import io.element.android.libraries.matrix.impl.core.SdkBackgroundTaskError
 import io.element.android.libraries.matrix.impl.mapper.toSessionData
 import io.element.android.libraries.matrix.impl.paths.getSessionPaths
 import io.element.android.libraries.matrix.impl.util.anonymizedTokens
 import io.element.android.libraries.sessionstorage.api.SessionStore
+import io.element.android.services.analytics.api.AnalyticsService
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import org.matrix.rustcomponents.sdk.ClientDelegate
 import org.matrix.rustcomponents.sdk.ClientSessionDelegate
@@ -23,6 +26,7 @@ import timber.log.Timber
 import uniffi.matrix_sdk_common.BackgroundTaskFailureReason
 import java.lang.ref.WeakReference
 import java.util.concurrent.atomic.AtomicBoolean
+import kotlin.time.Duration.Companion.milliseconds
 
 private val loggerTag = LoggerTag("RustClientSessionDelegate")
 
@@ -36,6 +40,7 @@ private val loggerTag = LoggerTag("RustClientSessionDelegate")
 class RustClientSessionDelegate(
     private val sessionStore: SessionStore,
     private val appCoroutineScope: CoroutineScope,
+    private val analyticsService: AnalyticsService,
     coroutineDispatchers: CoroutineDispatchers,
 ) : ClientSessionDelegate, ClientDelegate {
     // Used to ensure several calls to `didReceiveAuthError` don't trigger multiple logouts
@@ -122,8 +127,18 @@ class RustClientSessionDelegate(
     }
 
     override fun onBackgroundTaskErrorReport(taskName: String, error: BackgroundTaskFailureReason) {
-        // TODO actually implement the missing logic to report to sentry and crash the app
+        val backgroundTaskError = SdkBackgroundTaskError(taskName, error)
-        Timber.tag(loggerTag.value).e("onBackgroundTaskErrorReport(taskName=$taskName, error=$error)")
+        Timber.e(backgroundTaskError, "SDK background task failed")
+        analyticsService.trackError(backgroundTaskError)
+
+        if (error is BackgroundTaskFailureReason.Panic) {
+            appCoroutineScope.launch {
+                // The SDK failed in an unrecoverable way, so it will have indeterminate behaviour now.
+                // Crash the app instead after a small delay to send the error.
+                delay(500.milliseconds)
+                throw backgroundTaskError
+            }
+        }
     }
 
     override fun retrieveSessionFromKeychain(userId: String): Session {

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClientFactory.kt

@@ -66,7 +66,12 @@ class RustMatrixClientFactory(
     private val sqliteStoreBuilderProvider: SqliteStoreBuilderProvider,
     private val workManagerScheduler: WorkManagerScheduler,
 ) {
-    private val sessionDelegate = RustClientSessionDelegate(sessionStore, appCoroutineScope, coroutineDispatchers)
+    private val sessionDelegate = RustClientSessionDelegate(
+        sessionStore = sessionStore,
+        appCoroutineScope = appCoroutineScope,
+        analyticsService = analyticsService,
+        coroutineDispatchers = coroutineDispatchers
+    )
 
     suspend fun create(sessionData: SessionData): RustMatrixClient = withContext(coroutineDispatchers.io) {
         val client = getBaseClientBuilder(

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/core/SdkBackgroundTaskError.kt

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.impl.core
+
+import uniffi.matrix_sdk_common.BackgroundTaskFailureReason
+
+/**
+ * Error thrown when a background SDK task panics and can't recover.
+ * @param task The name of the task that failed.
+ * @param reason The cause of this error.
+ */
+class SdkBackgroundTaskError(
+    task: String,
+    reason: BackgroundTaskFailureReason,
+) : Error() {
+    override val message: String = run {
+        val message = when (reason) {
+            is BackgroundTaskFailureReason.EarlyTermination -> "Early termination"
+            is BackgroundTaskFailureReason.Error -> "Error: ${reason.error}"
+            is BackgroundTaskFailureReason.Panic -> buildString {
+                append("Panic (unrecoverable): ")
+                reason.message?.let { append(it) }
+                reason.panicBacktrace?.let {
+                    append("\n")
+                    append(it)
+                }
+            }
+        }
+        "SDK background task '$task' failure: \n$message"
+    }
+}

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/RustClientSessionDelegateTest.kt

@@ -9,16 +9,20 @@
 package io.element.android.libraries.matrix.impl
 
 import com.google.common.truth.Truth.assertThat
+import io.element.android.libraries.matrix.impl.core.SdkBackgroundTaskError
 import io.element.android.libraries.matrix.impl.fixtures.factories.aRustSession
 import io.element.android.libraries.sessionstorage.api.SessionStore
 import io.element.android.libraries.sessionstorage.test.InMemorySessionStore
 import io.element.android.libraries.sessionstorage.test.aSessionData
+import io.element.android.services.analytics.api.AnalyticsService
+import io.element.android.services.analytics.test.FakeAnalyticsService
 import io.element.android.tests.testutils.testCoroutineDispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.test.TestScope
 import kotlinx.coroutines.test.runCurrent
 import kotlinx.coroutines.test.runTest
 import org.junit.Test
+import uniffi.matrix_sdk_common.BackgroundTaskFailureReason
 
 @OptIn(ExperimentalCoroutinesApi::class)
 class RustClientSessionDelegateTest {
@@ -44,12 +48,37 @@ class RustClientSessionDelegateTest {
         assertThat(result!!.accessToken).isEqualTo("at")
         assertThat(result.refreshToken).isEqualTo("rt")
     }
+
+    @Test
+    fun `onBackgroundTaskErrorReport reports the error to analytics if recoverable`() = runTest {
+        val analyticsService = FakeAnalyticsService(isEnabled = true)
+        val sut = aRustClientSessionDelegate(analyticsService = analyticsService)
+        sut.onBackgroundTaskErrorReport("Crasher", BackgroundTaskFailureReason.EarlyTermination)
+        sut.onBackgroundTaskErrorReport("Crasher", BackgroundTaskFailureReason.Error("BOOM"))
+
+        assertThat(analyticsService.trackedErrors).hasSize(2)
+        assertThat(analyticsService.trackedErrors[0].message).isEqualTo("SDK background task 'Crasher' failure: \nEarly termination")
+        assertThat(analyticsService.trackedErrors[1].message).isEqualTo("SDK background task 'Crasher' failure: \nError: BOOM")
+    }
+
+    @Test(expected = SdkBackgroundTaskError::class)
+    fun `onBackgroundTaskErrorReport reports the error to analytics and throws it if it's a panic`() = runTest {
+        val analyticsService = FakeAnalyticsService(isEnabled = true)
+        val sut = aRustClientSessionDelegate(analyticsService = analyticsService)
+        sut.onBackgroundTaskErrorReport("Crasher", BackgroundTaskFailureReason.Panic("BOOM", "Stacktrace"))
+
+        assertThat(analyticsService.trackedErrors).hasSize(1)
+        assertThat(analyticsService.trackedErrors[0].message)
+            .isEqualTo("SDK background task 'Crasher' failure: \nPanic (unrecoverable): BOOM\nStacktrace")
+    }
 }
 
 fun TestScope.aRustClientSessionDelegate(
     sessionStore: SessionStore = InMemorySessionStore(),
+    analyticsService: AnalyticsService = FakeAnalyticsService(),
 ) = RustClientSessionDelegate(
     sessionStore = sessionStore,
     appCoroutineScope = this,
+    analyticsService = analyticsService,
     coroutineDispatchers = testCoroutineDispatchers(),
 )