First attempt

libraries/push/impl/src/main/kotlin/io/element/android/libraries/push/impl/workmanager/SyncNotificationWorkManagerRequest.kt

@@ -29,15 +29,13 @@ class SyncNotificationWorkManagerRequest(
     private val workerDataConverter: WorkerDataConverter,
     private val buildVersionSdkIntProvider: BuildVersionSdkIntProvider,
 ) : WorkManagerRequest {
-    override fun build(): Result<WorkRequest> {
+    override fun build(): List<Result<WorkRequest>> {
         if (notificationEventRequests.isEmpty()) {
-            return Result.failure(InvalidParameterException("notificationEventRequests cannot be empty"))
-        }
-        val data = workerDataConverter.serialize(notificationEventRequests).getOrElse {
-            return Result.failure(it)
+            return listOf(Result.failure(InvalidParameterException("notificationEventRequests cannot be empty")))
         }
         Timber.d("Scheduling ${notificationEventRequests.size} notification requests with WorkManager for $sessionId")
-        return Result.success(
+        return workerDataConverter.serialize(notificationEventRequests).map {
+            it.map { data ->
                 OneTimeWorkRequestBuilder<FetchNotificationsWorker>()
                     .setInputData(data)
                     .apply {
@@ -52,7 +50,8 @@ class SyncNotificationWorkManagerRequest(
                     // TODO investigate using this instead of the resolver queue
                     // .setInputMerger()
                     .build()
-        )
+            }
+        }
     }
 
     @Serializable

libraries/push/impl/src/main/kotlin/io/element/android/libraries/push/impl/workmanager/WorkerDataConverter.kt

@@ -12,6 +12,7 @@ import androidx.work.Data
 import androidx.work.workDataOf
 import dev.zacsweers.metro.Inject
 import io.element.android.libraries.androidutils.json.JsonProvider
+import io.element.android.libraries.core.extensions.mapCatchingExceptions
 import io.element.android.libraries.core.extensions.runCatchingExceptions
 import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.api.core.RoomId
@@ -23,12 +24,29 @@ import timber.log.Timber
 class WorkerDataConverter(
     private val json: JsonProvider,
 ) {
-    fun serialize(notificationEventRequests: List<NotificationEventRequest>): Result<Data> {
+    fun serialize(notificationEventRequests: List<NotificationEventRequest>): List<Result<Data>> {
+        return serializeRequests(notificationEventRequests)
+            .fold(
+                onSuccess = {
+                    listOf(Result.success(it))
+                },
+                onFailure = {
+                    // Perform serialization on sublists, workDataOf may have failed because of size limit
+                    Timber.w(it, "Failed to serialize ${notificationEventRequests.size} notification requests, trying with chunks of $CHUNK_SIZE.")
+                    notificationEventRequests.chunked(CHUNK_SIZE).map { chunk ->
+                        serializeRequests(chunk)
+                    }
+                },
+            )
+    }
+
+    private fun serializeRequests(notificationEventRequests: List<NotificationEventRequest>): Result<Data> {
         return runCatchingExceptions { json().encodeToString(notificationEventRequests.map { it.toData() }) }
             .onFailure {
                 Timber.e(it, "Failed to serialize notification requests")
             }
-            .map { str ->
+            .mapCatchingExceptions { str ->
+                // Note: workDataOf can fail if the data is too large
                 workDataOf(REQUESTS_KEY to str)
             }
     }
@@ -51,6 +69,7 @@ class WorkerDataConverter(
 
     companion object {
         private const val REQUESTS_KEY = "requests"
+        private const val CHUNK_SIZE = 20
     }
 }
 

libraries/workmanager/api/src/main/kotlin/io/element/android/libraries/workmanager/api/WorkManagerRequest.kt

@@ -11,5 +11,5 @@ package io.element.android.libraries.workmanager.api
 import androidx.work.WorkRequest
 
 interface WorkManagerRequest {
-    fun build(): Result<WorkRequest>
+    fun build(): List<Result<WorkRequest>>
 }

libraries/workmanager/impl/src/main/kotlin/io/element/android/libraries/workmanager/impl/DefaultWorkManagerScheduler.kt

@@ -27,15 +27,17 @@ class DefaultWorkManagerScheduler(
     private val workManager by lazy { WorkManager.getInstance(context) }
 
     override fun submit(workManagerRequest: WorkManagerRequest) {
-        workManagerRequest.build().fold(
-            onSuccess = {
-                workManager.enqueue(it)
+        workManagerRequest.build().forEach {
+            it.fold(
+                onSuccess = { workRequest ->
+                    workManager.enqueue(workRequest)
                 },
                 onFailure = {
                     Timber.e(it, "Failed to build WorkManager request $workManagerRequest")
                 }
             )
         }
+    }
 
     override fun cancel(sessionId: SessionId) {
         Timber.d("Cancelling work for sessionId: $sessionId")