ElementR| Retry query backup until it works during migration to avoid…

… spurious correption error popup (matrix-org#4113)

* retry query backup until it works during migration

* Add log line when fails to get backup during migration

src/rust-crypto/libolm_migration.ts

@@ -25,6 +25,8 @@ import { requestKeyBackupVersion } from "./backup";
 import { IRoomEncryption } from "../crypto/RoomList";
 import { CrossSigningKeyInfo } from "../crypto-api";
 import { RustCrypto } from "./rust-crypto";
+import { KeyBackupInfo } from "../crypto-api/keybackup";
+import { sleep } from "../utils";
 
 /**
  * Determine if any data needs migrating from the legacy store, and do so.
@@ -105,7 +107,7 @@ export async function migrateFromLegacyCrypto(args: {
 
     if (migrationState === MigrationState.NOT_STARTED) {
         logger.info("Migrating data from legacy crypto store. Step 1: base data");
-        await migrateBaseData(args.http, args.userId, args.deviceId, legacyStore, pickleKey, args.storeHandle);
+        await migrateBaseData(args.http, args.userId, args.deviceId, legacyStore, pickleKey, args.storeHandle, logger);
 
         migrationState = MigrationState.INITIAL_DATA_MIGRATED;
         await legacyStore.setMigrationState(migrationState);
@@ -144,6 +146,7 @@ async function migrateBaseData(
     legacyStore: CryptoStore,
     pickleKey: Uint8Array,
     storeHandle: RustSdkCryptoJs.StoreHandle,
+    logger: Logger,
 ): Promise<void> {
     const migrationData = new RustSdkCryptoJs.BaseMigrationData();
     migrationData.userId = new RustSdkCryptoJs.UserId(userId);
@@ -160,7 +163,18 @@ async function migrateBaseData(
     // If we have a backup recovery key, we need to try to figure out which backup version it is for.
     // All we can really do is ask the server for the most recent version.
     if (recoveryKey) {
-        const backupInfo = await requestKeyBackupVersion(http);
+        let backupCallDone = false;
+        let backupInfo: KeyBackupInfo | null = null;
+        while (!backupCallDone) {
+            try {
+                backupInfo = await requestKeyBackupVersion(http);
+                backupCallDone = true;
+            } catch (e) {
+                logger.info("Failed to get backup version during migration, retrying in 2 seconds", e);
+                // Retry until successful, use simple constant delay
+                await sleep(2000);
+            }
+        }
         if (backupInfo) {
             migrationData.backupVersion = backupInfo.version;
             migrationData.backupRecoveryKey = recoveryKey;