Fix potential performance issues during backup attachment upload.

app/src/main/java/org/thoughtcrime/securesms/backup/v2/ArchiveDatabaseExecutor.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.backup.v2
+
+import org.signal.core.util.ThreadUtil
+import org.signal.core.util.concurrent.SignalExecutors
+import org.thoughtcrime.securesms.dependencies.AppDependencies
+import org.thoughtcrime.securesms.util.ThrottledDebouncer
+import java.util.concurrent.ExecutionException
+import java.util.concurrent.Executors
+import kotlin.time.Duration.Companion.seconds
+
+/**
+ * During media upload/restore, we tend to hammer the database from a lot of different threads at once. This can block writes for more urgent things, like message
+ * sends. To reduce the impact, we put all of our database writes on a single-thread executor.
+ */
+object ArchiveDatabaseExecutor {
+
+  val executor = Executors.newSingleThreadExecutor(SignalExecutors.NumberedThreadFactory("archive-db", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD))
+
+  /**
+   * By default, downloading/uploading an attachment wants to notify a bunch of database observation listeners. This slams the observer so hard that other
+   * people using it will experience massive delays in notifications. To avoid this, we turn off notifications for downloads, and then use this notifier to
+   * push some out every so often.
+   */
+  val databaseObserverNotifier = ThrottledDebouncer(5.seconds.inWholeMilliseconds)
+
+  val notifyAttachmentObservers = {
+    AppDependencies.databaseObserver.notifyConversationListListeners()
+    AppDependencies.databaseObserver.notifyAttachmentUpdatedObservers()
+  }
+
+  val notifyAttachmentAndChatListObservers = {
+    AppDependencies.databaseObserver.notifyConversationListListeners()
+    AppDependencies.databaseObserver.notifyAttachmentUpdatedObservers()
+  }
+
+  fun <T> runBlocking(block: () -> T): T {
+    return try {
+      executor.submit(block).get()
+    } catch (e: ExecutionException) {
+      throw e.cause ?: e
+    }
+  }
+
+  fun throttledNotifyAttachmentObservers() {
+    databaseObserverNotifier.publish(notifyAttachmentObservers)
+  }
+
+  fun throttledNotifyAttachmentAndChatListObservers() {
+    databaseObserverNotifier.publish(notifyAttachmentAndChatListObservers)
+  }
+}