add progress notification and cancellation to key backup flush

src/matrix/Session.js

@@ -76,6 +76,7 @@ export class Session {
         this._getSyncToken = () => this.syncToken;
         this._olmWorker = olmWorker;
         this._keyBackup = null;
+        this._keyBackupOperation = new ObservableValue(null);
         this._hasSecretStorageKey = new ObservableValue(null);
         this._observedRoomStatus = new Map();
 
@@ -270,6 +271,10 @@ export class Session {
         return this._keyBackup;
     }
 
+    get keyBackupOperation() {
+        return this._keyBackupOperation;
+    }
+
     get hasIdentity() {
         return !!this._e2eeAccount;
     }
@@ -559,7 +564,7 @@ export class Session {
     async writeSync(syncResponse, syncFilterId, preparation, txn, log) {
         const changes = {
             syncInfo: null,
-            e2eeAccountChanges: null,
+            e2eeAccountChanges: null
         };
         const syncToken = syncResponse.next_batch;
         if (syncToken !== this.syncToken) {
@@ -584,7 +589,7 @@ export class Session {
             // this should come after the deviceMessageHandler, so the room keys are already written and their
             // isBetter property has been checked
             if (this._keyBackup) {
-                this._keyBackup.writeKeys(preparation.newRoomKeys, txn, log);
+                changes.shouldFlushKeyBackup = this._keyBackup.writeKeys(preparation.newRoomKeys, txn, log);
             }
         }
 
@@ -623,8 +628,18 @@ export class Session {
                 await log.wrap("uploadKeys", log => this._e2eeAccount.uploadKeys(this._storage, false, log));
             }
         }
-        if (this._keyBackup) {
-            this._keyBackup.flush();
+        // should flush and not already flushing
+        if (changes.shouldFlushKeyBackup && this._keyBackup && !this._keyBackupOperation.get()) {
+            log.wrapDetached("flush key backup", async log => {
+                const operation = this._keyBackup.flush(log);
+                this._keyBackupOperation.set(operation);
+                try {
+                    await operation.result;
+                } catch (err) {
+                    log.catch(err);
+                }
+                this._keyBackupOperation.set(null);
+            });
         }
     }
 

src/matrix/e2ee/megolm/keybackup/KeyBackup.ts

@@ -18,7 +18,10 @@ import {StoreNames} from "../../../storage/common";
 import {keyFromStorage, keyFromBackup} from "../decryption/RoomKey";
 import {MEGOLM_ALGORITHM} from "../../common";
 import * as Curve25519 from "./Curve25519";
+import {AbortableOperation} from "../../../../utils/AbortableOperation";
 
+import {SetAbortableFn} from "../../../../utils/AbortableOperation";
+import type {BackupInfo, SessionData, SessionKeyInfo, SessionInfo, KeyBackupPayload} from "./types";
 import type {HomeServerApi} from "../../../net/HomeServerApi";
 import type {IncomingRoomKey, RoomKey} from "../decryption/RoomKey";
 import type {KeyLoader} from "../decryption/KeyLoader";
@@ -27,6 +30,7 @@ import type {Storage} from "../../../storage/idb/Storage";
 import type {ILogItem} from "../../../../logging/types";
 import type {Platform} from "../../../../platform/web/Platform";
 import type {Transaction} from "../../../storage/idb/Transaction";
+import type {BackupEntry} from "../../../storage/idb/stores/SessionNeedingBackupStore";
 import type * as OlmNamespace from "@matrix-org/olm";
 type Olm = typeof OlmNamespace;
 
@@ -45,7 +49,7 @@ export class KeyBackup {
         if (!sessionResponse.session_data) {
             return;
         }
-        const sessionKeyInfo = this.crypto.decryptRoomKey(sessionResponse.session_data as Curve25519.SessionData);
+        const sessionKeyInfo = this.crypto.decryptRoomKey(sessionResponse.session_data as SessionData);
         if (sessionKeyInfo?.algorithm === MEGOLM_ALGORITHM) {
             return keyFromBackup(roomId, sessionId, sessionKeyInfo);
         } else if (sessionKeyInfo?.algorithm) {
@@ -64,45 +68,69 @@ export class KeyBackup {
         return hasBetter;
     }
 
-    async flush() {
-        while (true) {
-            await this.platform.clock.createTimeout(this.platform.random() * 10000).elapsed();
-            const txn = await this.storage.readTxn([
-                StoreNames.sessionsNeedingBackup,
-                StoreNames.inboundGroupSessions,
-            ]);
-            const keysNeedingBackup = await txn.sessionsNeedingBackup.getFirstEntries(20);
-            if (keysNeedingBackup.length === 0) {
-                return;
-            }
-            const roomKeys = await Promise.all(keysNeedingBackup.map(k => keyFromStorage(k.roomId, k.senderKey, k.sessionId, txn)));
-            const payload: KeyBackupPayload = { rooms: {} };
-            const payloadRooms = payload.rooms;
-            for (const key of roomKeys) {
-                if (key) {
-                    let roomPayload = payloadRooms[key.roomId];
-                    if (!roomPayload) {
-                       roomPayload = payloadRooms[key.roomId] = { sessions: {} };
-                    }
-                    roomPayload.sessions[key.sessionId] = await this.encodeRoomKey(key);
-                }
-            }
-            await this.hsApi.uploadRoomKeysToBackup(this.backupInfo.version, payload).response();
-            {
-                const txn = await this.storage.readWriteTxn([
+    // TODO: protect against having multiple concurrent flushes
+    flush(log: ILogItem): AbortableOperation<Promise<void>, Progress> {
+        return new AbortableOperation(async (setAbortable, setProgress) => {
+            let total = 0;
+            let amountFinished = 0;
+            while (true) {
+                const timeout = this.platform.clock.createTimeout(this.platform.random() * 10000);
+                setAbortable(timeout);
+                await timeout.elapsed();
+                const txn = await this.storage.readTxn([
                     StoreNames.sessionsNeedingBackup,
+                    StoreNames.inboundGroupSessions,
                 ]);
-                try {
-                    for (const key of keysNeedingBackup) {
-                        txn.sessionsNeedingBackup.remove(key.roomId, key.senderKey, key.sessionId);
-                    }
-                } catch (err) {
-                    txn.abort();
-                    throw err;
+                setAbortable(txn);
+                // fetch total again on each iteration as while we are flushing, sync might be adding keys
+                total = await txn.sessionsNeedingBackup.count();
+                setProgress(new Progress(total, amountFinished));
+                const keysNeedingBackup = await txn.sessionsNeedingBackup.getFirstEntries(20);
+                if (keysNeedingBackup.length === 0) {
+                    return;
                 }
-                await txn.complete();
+                const roomKeysOrNotFound = await Promise.all(keysNeedingBackup.map(k => keyFromStorage(k.roomId, k.senderKey, k.sessionId, txn)));
+                const roomKeys = roomKeysOrNotFound.filter(k => !!k) as RoomKey[];
+                if (roomKeys.length) {
+                    const payload = await this.encodeKeysForBackup(roomKeys);
+                    const uploadRequest = this.hsApi.uploadRoomKeysToBackup(this.backupInfo.version, payload);
+                    setAbortable(uploadRequest);
+                    await uploadRequest.response();
+                }
+                this.removeBackedUpKeys(keysNeedingBackup, setAbortable);
+                amountFinished += keysNeedingBackup.length;
+                setProgress(new Progress(total, amountFinished));
             }
+        });
+    }
+
+    private async encodeKeysForBackup(roomKeys: RoomKey[]): Promise<KeyBackupPayload> {
+        const payload: KeyBackupPayload = { rooms: {} };
+        const payloadRooms = payload.rooms;
+        for (const key of roomKeys) {
+            let roomPayload = payloadRooms[key.roomId];
+            if (!roomPayload) {
+               roomPayload = payloadRooms[key.roomId] = { sessions: {} };
+            }
+            roomPayload.sessions[key.sessionId] = await this.encodeRoomKey(key);
         }
+        return payload;
+    }
+
+    private async removeBackedUpKeys(keysNeedingBackup: BackupEntry[], setAbortable: SetAbortableFn) {
+        const txn = await this.storage.readWriteTxn([
+            StoreNames.sessionsNeedingBackup,
+        ]);
+        setAbortable(txn);
+        try {
+            for (const key of keysNeedingBackup) {
+                txn.sessionsNeedingBackup.remove(key.roomId, key.senderKey, key.sessionId);
+            }
+        } catch (err) {
+            txn.abort();
+            throw err;
+        }
+        await txn.complete();
     }
 
     private async encodeRoomKey(roomKey: RoomKey): Promise<SessionInfo> {
@@ -140,3 +168,10 @@ export class KeyBackup {
         }
     }
 }
+
+export class Progress {
+    constructor(
+        public readonly total: number,
+        public readonly finished: number
+    ) {}
+}

src/matrix/storage/idb/stores/SessionNeedingBackupStore.ts

@@ -53,4 +53,8 @@ export class SessionNeedingBackupStore {
     remove(roomId: string, senderKey: string, sessionId: string): void {
         this.store.delete(encodeKey(roomId, senderKey, sessionId));
     }
+
+    count(): Promise<number> {
+        return this.store.count();
+    }
 }