Fallback to global media tier CDN number

Co-authored-by: trevor-signal <131492920+trevor-signal@users.noreply.github.com>

ts/RemoteConfig.ts

@@ -41,6 +41,7 @@ export type ConfigKeyType =
   | 'desktop.releaseNotes.dev'
   | 'global.attachments.maxBytes'
   | 'global.attachments.maxReceiveBytes'
+  | 'global.backups.mediaTierFallbackCdnNumber'
   | 'global.calling.maxGroupCallRingSize'
   | 'global.groupsv2.groupSizeHardLimit'
   | 'global.groupsv2.maxGroupSize'

ts/test-electron/util/downloadAttachment_test.ts

@@ -17,6 +17,7 @@ import {
   AttachmentVariant,
   AttachmentPermanentlyUndownloadableError,
 } from '../../types/Attachment';
+import { updateRemoteConfig } from '../../test-both/helpers/RemoteConfigStub';
 
 describe('utils/downloadAttachment', () => {
   const baseAttachment = {
@@ -300,7 +301,8 @@ describe('utils/downloadAttachment', () => {
 describe('getCdnNumberForBackupTier', () => {
   let sandbox: sinon.SinonSandbox;
 
-  beforeEach(() => {
+  beforeEach(async () => {
+    await DataWriter.removeAll();
     sandbox = sinon.createSandbox();
     sandbox.stub(window.storage, 'get').callsFake(key => {
       if (key === 'masterKey') {
@@ -311,11 +313,19 @@ describe('getCdnNumberForBackupTier', () => {
       }
       return undefined;
     });
+    await updateRemoteConfig([
+      {
+        name: 'global.backups.mediaTierFallbackCdnNumber',
+        enabled: true,
+        value: '42',
+      },
+    ]);
   });
 
   afterEach(async () => {
     await DataWriter.clearAllBackupCdnObjectMetadata();
     sandbox.restore();
+    await updateRemoteConfig([]);
   });
 
   const baseAttachment = {
@@ -334,7 +344,7 @@ describe('getCdnNumberForBackupTier', () => {
       ...baseAttachment,
       backupLocator: { mediaName: 'mediaName' },
     });
-    assert.equal(result, 3);
+    assert.equal(result, 42);
   });
   it('uses cdn number in DB if none on attachment', async () => {
     await DataWriter.saveBackupCdnObjectMetadata([

ts/test-mock/bootstrap.ts

@@ -176,6 +176,7 @@ const DEFAULT_REMOTE_CONFIG = [
   ['desktop.internalUser', { enabled: true }],
   ['desktop.releaseNotes', { enabled: true }],
   ['desktop.senderKey.retry', { enabled: true }],
+  ['global.backups.mediaTierFallbackCdnNumber', { enabled: true, value: '3' }],
   ['global.groupsv2.groupSizeHardLimit', { enabled: true, value: '64' }],
   ['global.groupsv2.maxGroupSize', { enabled: true, value: '32' }],
 ] as const;

ts/textsecure/downloadAttachment.ts

@@ -46,8 +46,8 @@ import { MAX_BACKUP_THUMBNAIL_SIZE } from '../types/VisualAttachment';
 import { missingCaseError } from '../util/missingCaseError';
 import { IV_LENGTH, MAC_LENGTH } from '../types/Crypto';
 import { BackupCredentialType } from '../types/backups';
-
-const DEFAULT_BACKUP_CDN_NUMBER = 3;
+import { getValue } from '../RemoteConfig';
+import { parseIntOrThrow } from '../util/parseIntOrThrow';
 
 export function getCdnKey(attachment: ProcessedAttachment): string {
   const cdnKey = attachment.cdnId || attachment.cdnKey;
@@ -93,7 +93,10 @@ export async function getCdnNumberForBackupTier(
     if (backupCdnInfo.isInBackupTier) {
       backupCdnNumber = backupCdnInfo.cdnNumber;
     } else {
-      backupCdnNumber = DEFAULT_BACKUP_CDN_NUMBER;
+      backupCdnNumber = parseIntOrThrow(
+        getValue('global.backups.mediaTierFallbackCdnNumber'),
+        'global.backups.mediaTierFallbackCdnNumber must be set'
+      );
     }
   }
   return backupCdnNumber;