add MinIO tests (#381)

Extends workflow to test snapshots with minio.

.github/workflows/main.yml

@@ -16,7 +16,6 @@ jobs:
       matrix:
         python-version: [3.9]
         node-version: [14.x]
-
     steps:
       - uses: actions/checkout@v2
 
@@ -38,6 +37,12 @@ jobs:
       - name: Install Node.js packages
         run: yarn install
 
+      - name: Make sure bucket is versioned
+        env:
+          AWS_ACCESS_KEY_ID: administrator
+          AWS_SECRET_ACCESS_KEY: administrator
+        run: aws --region us-east-1 --endpoint-url http://localhost:9000 s3api put-bucket-versioning --bucket grist-docs-test --versioning-configuration Status=Enabled
+
       - name: Build Node.js code
         run: yarn run build:prod
 
@@ -47,8 +52,19 @@ jobs:
       - name: Run python tests
         run: yarn run test:python
 
-      - name: Run main tests
-        run: MOCHA_WEBDRIVER_HEADLESS=1 yarn run test
+      - name: Run server tests with minio and redis
+        run: MOCHA_WEBDRIVER_HEADLESS=1 yarn run test:server
+        env:
+          GRIST_DOCS_MINIO_ACCESS_KEY: administrator
+          GRIST_DOCS_MINIO_SECRET_KEY: administrator
+          TEST_REDIS_URL: "redis://localhost/11"
+          GRIST_DOCS_MINIO_USE_SSL: 0
+          GRIST_DOCS_MINIO_ENDPOINT: localhost
+          GRIST_DOCS_MINIO_PORT: 9000
+          GRIST_DOCS_MINIO_BUCKET: grist-docs-test
+
+      - name: Run main tests without minio and redis
+        run: MOCHA_WEBDRIVER_HEADLESS=1 yarn run test --exclude '_build/test/server/**/*'
 
       - name: Update candidate branch
         if: ${{ github.event_name == 'push' }}
@@ -57,3 +73,29 @@ jobs:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           branch: latest_candidate
           force: true
+
+    services:
+      # https://github.com/bitnami/bitnami-docker-minio/issues/16
+      minio:
+        image: bitnami/minio:latest
+        env:
+          MINIO_DEFAULT_BUCKETS: "grist-docs-test:public"
+          MINIO_ROOT_USER: administrator
+          MINIO_ROOT_PASSWORD: administrator
+        ports:
+          - 9000:9000
+        options: >-
+          --health-cmd "curl -f http://localhost:9000/minio/health/ready"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+      redis:
+        image: redis
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5

app/server/lib/ICreate.ts

@@ -30,6 +30,7 @@ export interface ICreate {
   // Return a string containing 1 or more HTML tags to insert into the head element of every
   // static page.
   getExtraHeadHtml?(): string;
+  getStorageOptions?(name: string): ICreateStorageOptions|undefined;
 }
 
 export interface ICreateActiveDocOptions {
@@ -40,6 +41,7 @@ export interface ICreateActiveDocOptions {
 }
 
 export interface ICreateStorageOptions {
+  name: string;
   check(): boolean;
   create(purpose: 'doc'|'meta', extraPrefix: string): ExternalStorage|undefined;
 }
@@ -117,5 +119,8 @@ export function makeSimpleCreator(opts: {
       elements.push(getThemeBackgroundSnippet());
       return elements.join('\n');
     },
+    getStorageOptions(name: string) {
+      return storage?.find(s => s.name === name);
+    }
   };
 }

app/server/lib/configureMinIOExternalStorage.ts

@@ -37,9 +37,11 @@ export function checkMinIOExternalStorage() {
   }).getAsBool();
   const accessKey = settings.flag('accessKey').requireString({
     envVar: ['GRIST_DOCS_MINIO_ACCESS_KEY'],
+    censor: true,
   });
   const secretKey = settings.flag('secretKey').requireString({
     envVar: ['GRIST_DOCS_MINIO_SECRET_KEY'],
+    censor: true,
   });
   settings.flag('url').set(`minio://${bucket}/${prefix}`);
   settings.flag('active').set(true);

stubs/app/server/lib/create.ts

@@ -8,6 +8,7 @@ export const create = makeSimpleCreator({
   sessionSecret: 'Phoo2ag1jaiz6Moo2Iese2xoaphahbai3oNg7diemohlah0ohtae9iengafieS2Hae7quungoCi9iaPh',
   storage: [
     {
+      name: 'minio',
       check: () => checkMinIOExternalStorage() !== undefined,
       create: configureMinIOExternalStorage,
     },

test/server/lib/HostedStorageManager.ts

@@ -0,0 +1,995 @@
+import {ErrorOrValue, freezeError, mapGetOrSet, MapWithTTL} from 'app/common/AsyncCreate';
+import {ObjMetadata, ObjSnapshot, ObjSnapshotWithMetadata} from 'app/common/DocSnapshot';
+import {DocWorkerMap} from 'app/gen-server/lib/DocWorkerMap';
+import {HomeDBManager} from 'app/gen-server/lib/HomeDBManager';
+import {ActiveDoc} from 'app/server/lib/ActiveDoc';
+import {create} from 'app/server/lib/create';
+import {DocManager} from 'app/server/lib/DocManager';
+import {makeExceptionalDocSession} from 'app/server/lib/DocSession';
+import {DELETED_TOKEN, ExternalStorage, wrapWithKeyMappedStorage} from 'app/server/lib/ExternalStorage';
+import {createDummyGristServer} from 'app/server/lib/GristServer';
+import {
+  BackupEvent,
+  backupSqliteDatabase,
+  HostedStorageManager,
+  HostedStorageOptions
+} from 'app/server/lib/HostedStorageManager';
+import log from 'app/server/lib/log';
+import {fromCallback} from 'app/server/lib/serverUtils';
+import {SQLiteDB} from 'app/server/lib/SQLiteDB';
+import * as bluebird from 'bluebird';
+import {assert} from 'chai';
+import * as fse from 'fs-extra';
+import * as path from 'path';
+import {createClient, RedisClient} from 'redis';
+import * as sinon from 'sinon';
+import {createInitialDb, removeConnection, setUpDB} from 'test/gen-server/seed';
+import {createTmpDir, getGlobalPluginManager} from 'test/server/docTools';
+import {setTmpLogLevel, useFixtureDoc} from 'test/server/testUtils';
+import {waitForIt} from 'test/server/wait';
+import uuidv4 from "uuid/v4";
+
+bluebird.promisifyAll(RedisClient.prototype);
+
+/**
+ * An in-memory store, for testing.
+ */
+class SimpleExternalStorage implements ExternalStorage {
+  protected _version = new Map<string, ObjSnapshot[]>();
+  private _nextId: number = 1;
+  private _memory = new Map<string, Buffer>();
+  private _metadata = new Map<string, ObjSnapshotWithMetadata>();
+
+  public constructor(public readonly label: string) {}
+
+  public async exists(key: string, snapshotId?: string): Promise<boolean> {
+    if (snapshotId) {
+      // Should check snapshotId is associated with key, but don't need to be too
+      // fussy this mock.
+      return this._memory.has(snapshotId);
+    }
+    return this._version.has(key);
+  }
+
+  public async head(key: string, snapshotId?: string) {
+    snapshotId = snapshotId || this._version.get(key)?.[0]?.snapshotId;
+    if (!snapshotId) { return null; }
+    return this._metadata.get(snapshotId) || null;
+  }
+
+  public async upload(key: string, fname: string, metadata?: ObjMetadata) {
+    const data = await fse.readFile(fname);
+    const id = `block-${this._nextId}`;
+    this._nextId++;
+    this._memory.set(id, data);
+    const info: ObjSnapshotWithMetadata = {
+      snapshotId: id,
+      lastModified: new Date().toISOString(),
+    };
+    this._metadata.set(id, {...info, ...metadata && {metadata}});
+    const versions = this._version.get(key) || [];
+    versions.unshift(info);
+    this._version.set(key, versions);
+    return id;
+  }
+
+  public async remove(key: string, snapshotIds?: string[]) {
+    const versions = this._version.get(key);
+    if (!versions) { return; }
+    if (!snapshotIds) {
+      for (const version of versions) {
+        this._memory.delete(version.snapshotId);
+        this._metadata.delete(version.snapshotId);
+      }
+      this._version.delete(key);
+    } else {
+      for (const snapshotId of snapshotIds) {
+        this._memory.delete(snapshotId);
+        this._metadata.delete(snapshotId);
+      }
+      const blockList = new Set(snapshotIds);
+      this._version.set(key, (this._version.get(key) || []).filter(v => !blockList.has(v.snapshotId)));
+    }
+  }
+
+  public async download(key: string, fname: string, snapshotId?: string) {
+    const versions = this._version.get(key);
+    if (!versions) { throw new Error('oopsie key not found'); }
+    if (snapshotId) {
+      if (!versions.find(v => v.snapshotId === snapshotId)) {
+        throw new Error('version not recognized');
+      }
+    } else {
+      snapshotId = versions[0].snapshotId;
+    }
+    if (!snapshotId) { throw new Error('version not found'); }
+    const data = this._memory.get(snapshotId);
+    if (!data) { throw new Error('version data not found'); }
+    await fse.writeFile(fname, data);
+    return snapshotId;
+  }
+
+  public async versions(key: string) {
+    return this._version.get(key) || [];
+  }
+
+  public url(key: string): string {
+    return `simple://test/${this.label}/${key}`;
+  }
+
+  public isFatalError(err: any): boolean {
+    return !String(err).includes('oopsie');
+  }
+
+  public async close() {
+    // nothing to do
+  }
+}
+
+/**
+ * A wrapper around an external store, that deliberately gives stale values for the
+ * `exists`, `download`, and `versions` methods.
+ */
+class CachedExternalStorage implements ExternalStorage {
+  private _cachedExists: MapWithTTL<string, Promise<ErrorOrValue<boolean>>>;
+  private _cachedHead: MapWithTTL<string, Promise<ErrorOrValue<ObjSnapshotWithMetadata|null>>>;
+  private _cachedDownload: MapWithTTL<string, Promise<ErrorOrValue<[string, Buffer]>>>;
+  private _cachedVersions: MapWithTTL<string, Promise<ErrorOrValue<ObjSnapshot[]>>>;
+
+  constructor(private _ext: ExternalStorage, ttlMs: number) {
+    this._cachedExists = new MapWithTTL(ttlMs);
+    this._cachedHead = new MapWithTTL(ttlMs);
+    this._cachedDownload = new MapWithTTL(ttlMs);
+    this._cachedVersions = new MapWithTTL(ttlMs);
+  }
+
+  public async exists(key: string, snapshotId?: string) {
+    const result = await mapGetOrSet(this._cachedExists, `${key}${snapshotId}`, () => {
+      return freezeError(this._ext.exists(key, snapshotId));
+    });
+    return result.unfreeze();
+  }
+
+  public async head(key: string, snapshotId?: string) {
+    const result = await mapGetOrSet(this._cachedHead, `${key}${snapshotId}`, () => {
+      return freezeError(this._ext.head(key, snapshotId));
+    });
+    return result.unfreeze();
+  }
+
+  public async upload(key: string, fname: string, metadata?: ObjMetadata) {
+    return this._ext.upload(key, fname, metadata);
+  }
+
+  public async remove(key: string, snapshotIds?: string[]) {
+    return this._ext.remove(key, snapshotIds);
+  }
+
+  public async download(key: string, fname: string, snapshotId?: string): Promise<string> {
+    const result = await mapGetOrSet(this._cachedDownload, `${key}${snapshotId}`, () => {
+      const altFname = fname + uuidv4();
+      return freezeError(
+        this._ext.download(key, altFname, snapshotId).then(async (v) => {
+          return [v, await fse.readFile(altFname)] as [string, Buffer];
+        })
+      );
+    });
+    try {
+      const [downloadedSnapshotId, txt] = await result.unfreeze();
+      await fse.writeFile(fname, txt);
+      return downloadedSnapshotId;
+    } catch (e) {
+      await fse.writeFile(fname, 'put some junk here to simulate unclean failure');
+      throw e;
+    }
+  }
+
+  public async versions(key: string) {
+    const result = await mapGetOrSet(this._cachedVersions, key, () => {
+      return freezeError(this._ext.versions(key));
+    });
+    return result.unfreeze();
+  }
+
+  public url(key: string): string {
+    return this._ext.url(key);
+  }
+
+  public isFatalError(err: any): boolean {
+    return this._ext.isFatalError(err);
+  }
+
+  public async close() {
+    // nothing to do
+  }
+}
+
+/**
+ * A wrapper that slows down responses from a store.
+ */
+class SlowExternalStorage implements ExternalStorage {
+  constructor(private _ext: ExternalStorage, private _delayMs: number) {}
+
+  public async exists(key: string, snapshotId?: string) {
+    await bluebird.delay(this._delayMs);
+    return this._ext.exists(key, snapshotId);
+  }
+
+  public async head(key: string, snapshotId?: string) {
+    await bluebird.delay(this._delayMs);
+    return this._ext.head(key, snapshotId);
+  }
+
+  public async upload(key: string, fname: string, metadata?: ObjMetadata) {
+    await bluebird.delay(this._delayMs);
+    return this._ext.upload(key, fname, metadata);
+  }
+
+  public async remove(key: string, snapshotIds?: string[]) {
+    await bluebird.delay(this._delayMs);
+    return this._ext.remove(key, snapshotIds);
+  }
+
+  public async download(key: string, fname: string, snapshotId?: string): Promise<string> {
+    await bluebird.delay(this._delayMs);
+    return this._ext.download(key, fname, snapshotId);
+  }
+
+  public async versions(key: string) {
+    await bluebird.delay(this._delayMs);
+    return this._ext.versions(key);
+  }
+
+  public url(key: string): string {
+    return this._ext.url(key);
+  }
+
+  public isFatalError(err: any): boolean {
+    return this._ext.isFatalError(err);
+  }
+
+  public async close() {
+    // nothing to do
+  }
+}
+
+
+/**
+ * A document store representing a doc worker's local store, for testing.
+ * Uses TEST_S3_BUCKET and TEST_S3_PREFIX.  Objects in test bucket should be set up
+ * to be deleted after a short period.  Since we don't attempt to garbage collect
+ * within the unit test.  s3://grist-docs-test/unit-tests/... is set up that way.
+ */
+class TestStore {
+  public docManager: DocManager;
+  public storageManager: HostedStorageManager;
+  private _active: boolean = false;  // True if the simulated doc worker is started.
+  private _extraPrefix = uuidv4();   // Extra prefix in S3 (unique to this test).
+
+  public constructor(
+    private _localDirectory: string,
+    private _workerId: string,
+    private _workers: DocWorkerMap,
+    private _externalStorageCreate: (purpose: 'doc'|'meta', extraPrefix: string) => ExternalStorage|undefined) {
+  }
+
+  // Simulates doc worker startup.
+  public async begin() {
+    await this.end();
+    this._active = true;
+    const dbManager = new HomeDBManager();
+    await dbManager.connect();
+    await dbManager.initializeSpecialIds();
+    const options: HostedStorageOptions = {
+      secondsBeforePush: 0.5,
+      secondsBeforeFirstRetry: 3,   // rumors online suggest delays of 10-11 secs
+                                    // are not super-unusual.
+      pushDocUpdateTimes: false,
+      externalStorageCreator: (purpose) => {
+        const result = this._externalStorageCreate(purpose, this._extraPrefix);
+        if (!result) { throw new Error('no storage'); }
+        return result;
+      }
+    };
+    const storageManager = new HostedStorageManager(this._localDirectory,
+                                                    this._workerId,
+                                                    false,
+                                                    this._workers,
+                                                    dbManager,
+                                                    create,
+                                                    options);
+    this.storageManager = storageManager;
+    this.docManager = new DocManager(storageManager, await getGlobalPluginManager(),
+                                     dbManager, {
+                                       ...createDummyGristServer(),
+                                       getStorageManager() { return storageManager; },
+                                     });
+  }
+
+  // Simulates doc worker shutdown.  Closes all open documents.
+  public async end() {
+    if (this._active) {
+      await this.docManager.shutdownAll();
+    }
+    this._active = false;
+  }
+
+  // Close a single doc.  The server does this for docs that are not open by
+  // any client.
+  public async closeDoc(doc: ActiveDoc) {
+    await doc.shutdown();
+  }
+
+  // Waits for any required S3 pushes to have completed.
+  public async waitForUpdates(): Promise<boolean> {
+    for (let i = 0; i < 50; i++) {
+      if (!this.storageManager.needsUpdate()) {
+        return true;
+      }
+      await bluebird.delay(100);
+    }
+    log.error("waitForUpdates failed");
+    return false;
+  }
+
+  // Wipes the doc worker's local document store.
+  public async removeAll(): Promise<void> {
+    const fnames = await fse.readdir(this._localDirectory);
+    await Promise.all(fnames.map(fname => {
+      return fse.remove(path.join(this._localDirectory, fname));
+    }));
+  }
+
+  public getDocPath(docId: string) {
+    return path.join(this._localDirectory, `${docId}.grist`);
+  }
+}
+
+
+describe('HostedStorageManager', function() {
+
+  setTmpLogLevel('info');  // allow info messages for this test since failures are hard to replicate
+  this.timeout(60000);     // s3 can be slow
+
+  const docSession = makeExceptionalDocSession('system');
+
+  before(async function() {
+    setUpDB(this);
+    await createInitialDb();
+  });
+
+  after(async function() {
+    await removeConnection();
+  });
+
+  for (const storage of ['azure', 's3', 'minio', 'cached'] as const) {
+    describe(storage, function() {
+
+      const sandbox = sinon.createSandbox();
+
+      const workerId = 'dw17';
+      let cli: RedisClient;
+      let store: TestStore;
+      let workers: DocWorkerMap;
+      let tmpDir: string;
+
+      before(async function() {
+        if (!process.env.TEST_REDIS_URL) { this.skip(); return; }
+        cli = createClient(process.env.TEST_REDIS_URL);
+        await cli.flushdbAsync();
+        workers = new DocWorkerMap([cli]);
+        await workers.addWorker({
+          id: workerId,
+          publicUrl: 'notset',
+          internalUrl: 'notset',
+        });
+        await workers.setWorkerAvailability(workerId, true);
+
+        await workers.assignDocWorker('Hello');
+        await workers.assignDocWorker('Hello2');
+
+        tmpDir = await createTmpDir();
+
+        let externalStorageCreate: (purpose: 'doc'|'meta', extraPrefix: string) => ExternalStorage|undefined;
+        function requireStorage<T>(storage: T|undefined): T {
+          if (storage === undefined) { throw new Error('storage not found'); }
+          return storage;
+        };
+        switch (storage) {
+          case 'cached': {
+            // Make an in-memory store that is slow and aggressively cached.
+            // This tickles a lot of cases that occasionally happen with s3.
+            let ext: ExternalStorage = new SimpleExternalStorage("bucket");
+            ext = new CachedExternalStorage(ext, 1000);
+            ext = new SlowExternalStorage(ext, 250);
+            // Everything is stored in fields of these objects, so the tests mustn't recreate them repeatedly.
+            externalStorageCreate = (purpose) => wrapWithKeyMappedStorage(ext, {purpose, basePrefix: 'prefix'});
+            break;
+          }
+          case 'azure':
+            if (!process.env.AZURE_STORAGE_CONNECTION_STRING) {
+              this.skip();
+            }
+            externalStorageCreate = requireStorage(create.getStorageOptions?.('azure')?.create);
+            break;
+          case 'minio':
+            if (!process.env.GRIST_DOCS_MINIO_ACCESS_KEY) {
+              this.skip();
+            }
+            externalStorageCreate = requireStorage(create.getStorageOptions?.('minio')?.create);
+            break;
+          case 's3':
+            if (!process.env.TEST_S3_BUCKET) {
+              this.skip();
+            }
+            externalStorageCreate = requireStorage(create.getStorageOptions?.('s3')?.create);
+            break;
+        }
+        store = new TestStore(tmpDir, workerId, workers, externalStorageCreate);
+      });
+
+      after(async function() {
+        await store?.storageManager.testStopOperations();
+        await workers?.removeWorker(workerId);
+        await cli?.quitAsync();
+      });
+
+      beforeEach(function() {
+        sandbox.spy(HostedStorageManager.prototype, 'markAsChanged');
+      });
+
+      afterEach(async function() {
+        sandbox.restore();
+        if (store) {
+          await store.end();
+          await store.removeAll();
+        }
+      });
+
+      async function getRedisChecksum(docId: string): Promise<string> {
+        return (await cli.getAsync(`doc-${docId}-checksum`)) || '';
+      }
+
+      async function setRedisChecksum(docId: string, checksum: string): Promise<'OK'> {
+        return cli.setAsync(`doc-${docId}-checksum`, checksum);
+      }
+
+      async function dropAllChecksums() {
+        // `keys` is a potentially slow, unrecommended operation - but ok in test scenario
+        // against a test instance of redis.
+        for (const key of await cli.keysAsync('*-checksum')) {
+          await cli.delAsync(key);
+        }
+      }
+
+      it('can create a fresh empty document', async function() {
+        const docId = `create-${uuidv4()}`;
+        await workers.assignDocWorker(docId);
+        assert.equal(await getRedisChecksum(docId), 'null');
+
+        // Create an empty document when checksum in redis is 'null'.
+        await store.begin();
+        await store.docManager.fetchDoc(docSession, docId);
+        assert(await store.waitForUpdates());
+        const checksum = await getRedisChecksum(docId);
+        assert.notEqual(checksum, 'null');
+        await store.end();
+
+        // Check if we nobble the expected checksum then fetch eventually errors.
+        await setRedisChecksum(docId, 'nobble');
+        await store.removeAll();
+        await store.begin();
+        await assert.isRejected(store.docManager.fetchDoc(docSession, docId),
+                                /operation failed to become consistent/);
+        await store.end();
+
+        // Check we get the document back on fresh start if checksum is correct.
+        await setRedisChecksum(docId, checksum);
+        await store.removeAll();
+        await store.begin();
+        await store.docManager.fetchDoc(docSession, docId);
+        await store.end();
+      });
+
+      it('can save modifications', async function() {
+        await store.begin();
+
+        await workers.assignDocWorker('Hello');
+        await useFixtureDoc('Hello.grist', store.storageManager);
+
+        await workers.assignDocWorker('Hello2');
+
+        let doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        let doc2 = await store.docManager.fetchDoc(docSession, 'Hello2');
+        await doc.docStorage.exec("update Table1 set A = 'magic_word' where id = 1");
+        await doc2.docStorage.exec("insert into Table1(id) values(42)");
+        await store.end();
+
+        await store.removeAll();
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        let result = await doc.docStorage.get("select A from Table1 where id = 1");
+        assert.equal(result!.A, 'magic_word');
+        doc2 = await store.docManager.fetchDoc(docSession, 'Hello2');
+        result = await doc2.docStorage.get("select id from Table1");
+        assert.equal(result!.id, 42);
+        await store.end();
+      });
+
+      it('can save modifications with interfering backup file', async function() {
+        await store.begin();
+
+        // There was a bug where if a corrupt/truncated backup file was created, all future
+        // backups would fail.  This tickles the condition and makes sure backups now succeed.
+        await fse.writeFile(path.join(tmpDir, 'Hello.grist-backup'), 'not a sqlite file');
+
+        await workers.assignDocWorker('Hello');
+        await useFixtureDoc('Hello.grist', store.storageManager);
+
+        let doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        await doc.docStorage.exec("update Table1 set A = 'magic_word2' where id = 1");
+        await store.end();  // S3 push will happen prior to this returning.
+
+        await store.removeAll();
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        const result = await doc.docStorage.get("select A from Table1 where id = 1");
+        assert.equal(result!.A, 'magic_word2');
+        await store.end();
+      });
+
+      it('survives if there is a doc marked dirty that turns out to be clean', async function() {
+        await store.begin();
+
+        await workers.assignDocWorker('Hello');
+        await useFixtureDoc('Hello.grist', store.storageManager);
+
+        let doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        await doc.docStorage.exec("update Table1 set A = 'magic_word' where id = 1");
+        await store.end();
+
+        await store.removeAll();
+
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        const result = await doc.docStorage.get("select A from Table1 where id = 1");
+        assert.equal(result!.A, 'magic_word');
+        store.docManager.markAsChanged(doc);
+        await store.end();
+
+        // The real test is whether this test manages to complete.
+      });
+
+      it('serializes parallel opening of same document', async function() {
+        await workers.assignDocWorker('Hello');
+
+        // put a doc in s3
+        await store.begin();
+        await useFixtureDoc('Hello.grist', store.storageManager);
+        let doc = await store.docManager.fetchDoc(docSession, 'Hello');
+        await doc.docStorage.exec("update Table1 set A = 'parallel' where id = 1");
+        await store.end();
+
+        // now open it many times in parallel
+        await store.removeAll();
+        await store.begin();
+        const docs = Promise.all([
+          store.docManager.fetchDoc(docSession, 'Hello'),
+          store.docManager.fetchDoc(docSession, 'Hello'),
+          store.docManager.fetchDoc(docSession, 'Hello'),
+          store.docManager.fetchDoc(docSession, 'Hello'),
+        ]);
+        await assert.isFulfilled(docs);
+        doc = (await docs)[0];
+        const result = await doc.docStorage.get("select A from Table1 where id = 1");
+        assert.equal(result!.A, 'parallel');
+        await store.end();
+
+        // To be sure we are checking something, let's call prepareLocalDoc directly
+        // on storage manager and make sure it fails.
+        await store.removeAll();
+        await store.begin();
+        const preps = Promise.all([
+          store.storageManager.prepareLocalDoc('Hello'),
+          store.storageManager.prepareLocalDoc('Hello'),
+          store.storageManager.prepareLocalDoc('Hello'),
+          store.storageManager.prepareLocalDoc('Hello')
+        ]);
+        await assert.isRejected(preps, /in parallel/);
+        await store.end();
+      });
+
+      it ('can delete a document', async function() {
+        const docId = `create-${uuidv4()}`;
+        await workers.assignDocWorker(docId);
+
+        // Create a document
+        await store.begin();
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("insert into Table1(id) values(42)");
+        await store.end();
+
+        const docPath = store.getDocPath(docId);
+        const ext = store.storageManager.testGetExternalStorage();
+
+        // Check that the document exists on filesystem and in external store.
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        assert.equal(await fse.pathExists(docPath), true);
+        assert.equal(await fse.pathExists(docPath + '-hash-doc'), true);
+        await waitForIt(async () => assert.equal(await ext.exists(docId), true), 20000);
+        await doc.docStorage.exec("insert into Table1(id) values(43)");
+
+        // Now delete the document, and check it no longer exists on filesystem or external store.
+        await store.docManager.deleteDoc(null, docId, true);
+        assert.equal(await fse.pathExists(docPath), false);
+        assert.equal(await fse.pathExists(docPath + '-hash-doc'), false);
+        assert.equal(await getRedisChecksum(docId), DELETED_TOKEN);
+        await waitForIt(async () => assert.equal(await ext.exists(docId), false), 20000);
+        await store.end();
+
+        // As far as the underlying storage is concerned it should be
+        // possible to recreate a doc with the same id after deletion.
+        // This should not happen in Grist, since in order to open a
+        // document it must exist in the db - however we'll need to watch
+        // out for caching.
+        // TODO: it could be worth tweaking fetchDoc so creation is explicit.
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("insert into Table1(id) values(42)");
+        await store.end();
+
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        assert.equal(await fse.pathExists(docPath), true);
+        assert.equal(await fse.pathExists(docPath + '-hash-doc'), true);
+        await store.end();
+      });
+
+      it('individual document close is orderly', async function() {
+        const docId = `create-${uuidv4()}`;
+        await workers.assignDocWorker(docId);
+
+        await store.begin();
+
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await store.closeDoc(doc);
+        const checksum1 = await getRedisChecksum(docId);
+        assert.notEqual(checksum1, 'null');
+
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("insert into Table1(id) values(42)");
+
+        // Add an attachment file with no corresponding metadata. It should be deleted when shutting down.
+        await doc.docStorage.exec("insert into _gristsys_Files(id, ident) values(23, 'foo')");
+        let files = await doc.docStorage.all("select * from _gristsys_Files");
+        assert.isNotEmpty(files);
+
+        await store.closeDoc(doc);
+        const checksum2 = await getRedisChecksum(docId);
+        assert.notEqual(checksum1, checksum2);
+
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("insert into Table1(id) values(43)");
+
+        // Attachment file should have been deleted on previous close.
+        files = await doc.docStorage.all("select * from _gristsys_Files");
+        assert.isEmpty(files);
+
+        const asyncClose = store.closeDoc(doc);  // this time, don't explicitly wait for closeDoc.
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        const checksum3 = await getRedisChecksum(docId);
+        assert.notEqual(checksum2, checksum3);
+        await asyncClose;
+
+        await store.end();
+      });
+
+      // Viewing a document should not mark it as changed (unless a document-level migration
+      // needed to run).
+      it('viewing a document does not generally change it', async function() {
+        const docId = `create-${uuidv4()}`;
+        await workers.assignDocWorker(docId);
+
+        await store.begin();
+
+        const markAsChanged: {callCount: number} = store.storageManager.markAsChanged as any;
+
+        const changesInitial = markAsChanged.callCount;
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.waitForInitialization();
+        await store.closeDoc(doc);
+        const changesAfterCreation = markAsChanged.callCount;
+        assert.isAbove(changesAfterCreation, changesInitial);
+
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.waitForInitialization();
+        await store.closeDoc(doc);
+        const changesAfterViewing = markAsChanged.callCount;
+        assert.equal(changesAfterViewing, changesAfterCreation);
+
+        await store.end();
+      });
+
+      it('can fork documents', async function() {
+        const docId = `create-${uuidv4()}`;
+        const forkId = `${docId}~fork1`;
+        await workers.assignDocWorker(docId);
+        await workers.assignDocWorker(forkId);
+
+        await store.begin();
+        await useFixtureDoc('Hello.grist', store.storageManager, `${docId}.grist`);
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("update Table1 set A = 'trunk' where id = 1");
+        await store.end();
+
+        await store.begin();
+        await store.docManager.storageManager.prepareFork(docId, forkId);
+        doc = await store.docManager.fetchDoc(docSession, forkId);
+        assert.equal('trunk', (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        await doc.docStorage.exec("update Table1 set A = 'fork' where id = 1");
+        await store.end();
+
+        await store.removeAll();
+
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        assert.equal('trunk', (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        doc = await store.docManager.fetchDoc(docSession, forkId);
+        assert.equal('fork', (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        await store.end();
+
+        // Check that the trunk can be replaced by a fork
+        await store.removeAll();
+        await store.begin();
+        await store.storageManager.replace(docId, {sourceDocId: forkId});
+        doc = await store.docManager.fetchDoc(docSession, docId);
+        assert.equal('fork', (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        await store.end();
+      });
+
+      it('can persist a fork with no modifications', async function() {
+        const docId = `create-${uuidv4()}`;
+        const forkId = `${docId}~fork1`;
+        await workers.assignDocWorker(docId);
+        await workers.assignDocWorker(forkId);
+
+        // Create a document.
+        await store.begin();
+        await useFixtureDoc('Hello.grist', store.storageManager, `${docId}.grist`);
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.docStorage.exec("update Table1 set A = 'trunk' where id = 1");
+        await store.end();
+
+        // Create a fork with no modifications.
+        await store.begin();
+        await store.docManager.storageManager.prepareFork(docId, forkId);
+        await store.end();
+        await store.waitForUpdates();
+        await store.removeAll();
+
+        // Zap local copy of fork.
+        await fse.remove(store.getDocPath(docId));
+
+        // Make sure opening the fork works as expected.
+        await store.begin();
+        doc = await store.docManager.fetchDoc(docSession, forkId);
+        assert.equal('trunk', (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        await store.end();
+        await store.removeAll();
+      });
+
+      it('can access snapshots', async function() {
+        // Keep number of forks less than 5 so pruning doesn't kick in.
+        const forks = 4;
+
+        const docId = `create-${uuidv4()}`;
+        const forkId1 = `${docId}~fork1`;
+        const forkId2 = `${docId}~fork2`;
+        const forkId3 = `${docId}~fork3`;
+        await workers.assignDocWorker(docId);
+        await workers.assignDocWorker(forkId1);
+        await workers.assignDocWorker(forkId2);
+        await workers.assignDocWorker(forkId3);
+
+        await store.begin();
+        await useFixtureDoc('Hello.grist', store.storageManager, `${docId}.grist`);
+        let doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.waitForInitialization();
+        for (let i = 0; i < forks; i++) {
+          await doc.docStorage.exec(`update Table1 set A = 'v${i}' where id = 1`);
+          await doc.testKeepOpen();
+          await store.waitForUpdates();
+        }
+        await store.end();
+
+        const {snapshots} = await store.storageManager.getSnapshots(doc.docName);
+        assert.isAtLeast(snapshots.length, forks + 1);  // May be 1 greater depending on how long
+        // it takes to run initial migrations.
+        await store.begin();
+        for (let i = forks - 1; i >= 0; i--) {
+          const snapshot = snapshots.shift()!;
+          const forkId = snapshot.docId;
+          await workers.assignDocWorker(forkId);
+          doc = await store.docManager.fetchDoc(docSession, forkId);
+          assert.equal(`v${i}`, (await doc.docStorage.get("select A from Table1 where id = 1"))!.A);
+        }
+        await store.end();
+      });
+
+      it('can prune snapshots', async function() {
+        const versions = 8;
+
+        const docId = `create-${uuidv4()}`;
+        await store.begin();
+        await useFixtureDoc('Hello.grist', store.storageManager, `${docId}.grist`);
+        const doc = await store.docManager.fetchDoc(docSession, docId);
+        for (let i = 0; i < versions; i++) {
+          await doc.docStorage.exec(`update Table1 set A = 'v${i}' where id = 1`);
+          await doc.testKeepOpen();
+          await store.waitForUpdates();
+        }
+        await store.storageManager.testWaitForPrunes();
+        await store.end();
+        await waitForIt(async () => {
+          const {snapshots} = await store.storageManager.getSnapshots(doc.docName);
+          // Should be keeping at least five, and then maybe 1 more if the hour changed
+          // during the test.
+          assert.isAtMost(snapshots.length, 6);
+          assert.isAtLeast(snapshots.length, 5);
+        }, 20000);
+        await waitForIt(async () => {
+          // Double check with external store directly.
+          const snapshots = await store.storageManager.testGetExternalStorage().versions(doc.docName);
+          assert.isAtMost(snapshots.length, 6);
+          assert.isAtLeast(snapshots.length, 5);
+        }, 20000);
+      });
+
+      for (const wipeLocal of [false, true]) {
+        it (`can lose checksums without disruption with${wipeLocal ? '' : 'out'} local file wipe`, async function() {
+          const docId = `create-${uuidv4()}`;
+          await workers.assignDocWorker(docId);
+
+          // Create a series of versions of a document, and fetch them sequentially
+          // so that they are potentially available as stale values.
+          await store.begin();
+          await useFixtureDoc('Hello.grist', store.storageManager, `${docId}.grist`);
+          let doc = await store.docManager.fetchDoc(docSession, docId);
+          await store.end();
+          for (let i = 0; i < 3; i++) {
+            await store.removeAll();
+            await store.begin();
+            doc = await store.docManager.fetchDoc(docSession, docId);
+            if (i > 0) {
+              const prev = await doc.docStorage.get("select A from Table1 where id = 1");
+              assert.equal(prev!.A, `magic_word${i - 1}`);
+            }
+            await doc.docStorage.exec(`update Table1 set A = 'magic_word${i}' where id = 1`);
+            await store.end();
+          }
+
+          // Wipe all checksums and make sure (1) we don't get any errors and (2) the
+          // right version of the document shows up after a while.
+          let result: string | undefined;
+          await waitForIt(async () => {
+            await dropAllChecksums();
+            if (wipeLocal) {
+              // Optionally wipe all local files.
+              await store.removeAll();
+            }
+            await store.begin();
+            doc = await store.docManager.fetchDoc(docSession, docId);
+            result = (await doc.docStorage.get("select A from Table1 where id = 1"))?.A;
+            await store.end();
+            if (result !== 'magic_word2') {
+              throw new Error(`inconsistent result: ${result}`);
+            }
+          }, 20000);
+          assert.equal(result, 'magic_word2');
+        });
+      }
+
+      it('can access metadata', async function() {
+        const docId = `create-${uuidv4()}`;
+        await store.begin();
+        // Use a doc that's up-to-date on storage migrations, but needs a python schema migration.
+        await useFixtureDoc('BlobMigrationV8.grist', store.storageManager, `${docId}.grist`);
+        const doc = await store.docManager.fetchDoc(docSession, docId);
+        await doc.waitForInitialization();
+        const rec = await doc.fetchTable(makeExceptionalDocSession('system'), '_grist_DocInfo');
+        const tz = rec[3].timezone[0];
+        const h = (await doc.getRecentStates(makeExceptionalDocSession('system')))[0].h;
+        await store.docManager.makeBackup(doc, 'hello');
+        await store.end();
+        const {snapshots} = await store.storageManager.getSnapshots(doc.docName);
+        assert.equal(snapshots[0]?.metadata?.label, 'hello');
+        // There can be extra snapshots, depending on timing.
+        const prevSnapshotWithLabel = snapshots.find((s, idx) => idx > 0 && s.metadata?.label);
+        assert.match(String(prevSnapshotWithLabel?.metadata?.label), /migrate-schema/);
+        assert.equal(snapshots[0]?.metadata?.tz, String(tz));
+        assert.equal(snapshots[0]?.metadata?.h, h);
+      });
+    });
+  }
+});
+
+// This is a performance test, to check if the backup settings are plausible.
+describe('backupSqliteDatabase', async function() {
+  it('backups are robust to locking', async function() {
+    // Takes some time to create large db and play with it.
+    this.timeout(20000);
+
+    const tmpDir = await createTmpDir();
+    const src = path.join(tmpDir, "src.db");
+    const dest = path.join(tmpDir, "dest.db");
+    const db = await SQLiteDB.openDBRaw(src);
+    await db.run("create table data(x,y,z)");
+    await db.execTransaction(async () => {
+      const stmt = await db.prepare("INSERT INTO data VALUES (?,?,?)");
+      for (let i = 0; i < 10000; i++) {
+        // Silly code to make a long random string to insert.
+        // We can make a big db faster this way.
+        const str = (new Array(100)).fill(1).map((_: any) => Math.random().toString(2)).join();
+        stmt.run(str, str, str);
+      }
+      await fromCallback(cb => stmt.finalize(cb));
+    });
+    const stat = await fse.stat(src);
+    assert(stat.size > 150 * 1000 * 1000);
+    let done: boolean = false;
+    let eventStart: number = 0;
+    let eventAction: string = "";
+    let eventCount: number = 0;
+    function progress(event: BackupEvent) {
+      if (event.phase === 'after') {
+        // Duration of backup action should never approach the default node-sqlite3 busy_timeout of 1s.
+        // If it does, then user actions could be blocked.
+        assert.equal(event.action, eventAction);
+        assert.isBelow(Date.now() - eventStart, 100);
+        eventCount++;
+      } else if (event.phase === 'before') {
+        eventStart = Date.now();
+        eventAction = event.action;
+      }
+    }
+    let backupError: Error|undefined;
+    const act = backupSqliteDatabase(src, dest, progress).then(() => done = true)
+      .catch((e) => { done = true; backupError = e; });
+    assert(!done);
+    // Try a series of insertions, to check that db never appears locked to us.
+    for (let i = 0; i < 100; i++) {
+      await bluebird.delay(10);
+      try {
+        await db.exec('INSERT INTO data VALUES (1,2,3)');
+      } catch (e) {
+        log.error('insertion failed, that is bad news, the db was locked for too long');
+        throw e;
+      }
+    }
+    assert(!done);
+
+    // Lock the db up completely for a while.
+    await db.exec('PRAGMA locking_mode = EXCLUSIVE');
+    await db.exec('BEGIN EXCLUSIVE');
+    await bluebird.delay(500);
+    await db.exec('COMMIT');
+    await db.exec('PRAGMA locking_mode = NORMAL');
+
+    assert(!done);
+    while (!done) {
+      // Make sure regular queries don't get in the way of backup completing
+      await db.all('select * from data limit 100');
+      await bluebird.delay(100);
+    }
+    await act;
+    if (backupError) { throw backupError; }
+
+    // Make sure we are receiving backup events and checking their timing.
+    assert.isAbove(eventCount, 100);
+
+    // Finally, check the backup looks sane.
+    const db2 = await SQLiteDB.openDBRaw(dest);
+    assert.lengthOf(await db2.all('select rowid from data'), 10000 + 100);
+  });
+});