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| /**
* Copyright 2017 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import { User } from '../auth/user';
import { DatabaseInfo } from '../core/database_info';
import { JsonProtoSerializer } from '../remote/serializer';
import { assert } from '../util/assert';
import { Code, FirestoreError } from '../util/error';
import * as log from '../util/log';
import { AutoId } from '../util/misc';
import { IndexedDbMutationQueue } from './indexeddb_mutation_queue';
import { IndexedDbQueryCache } from './indexeddb_query_cache';
import { IndexedDbRemoteDocumentCache } from './indexeddb_remote_document_cache';
import { ALL_STORES, DbOwner, DbOwnerKey } from './indexeddb_schema';
import { createOrUpgradeDb, SCHEMA_VERSION } from './indexeddb_schema';
import { LocalSerializer } from './local_serializer';
import { MutationQueue } from './mutation_queue';
import { Persistence } from './persistence';
import { PersistencePromise } from './persistence_promise';
import { QueryCache } from './query_cache';
import { RemoteDocumentCache } from './remote_document_cache';
import { SimpleDb, SimpleDbTransaction } from './simple_db';
const LOG_TAG = 'IndexedDbPersistence';
/** If the owner lease is older than 5 seconds, try to take ownership. */
const OWNER_LEASE_MAX_AGE_MS = 5000;
/** Refresh the owner lease every 4 seconds while owner. */
const OWNER_LEASE_REFRESH_INTERVAL_MS = 4000;
/** LocalStorage location to indicate a zombied ownerId (see class comment). */
const ZOMBIE_OWNER_LOCALSTORAGE_SUFFIX = 'zombiedOwnerId';
/** Error when the owner lease cannot be acquired or is lost. */
const EXISTING_OWNER_ERROR_MSG =
'There is another tab open with offline' +
' persistence enabled. Only one such tab is allowed at a time. The' +
' other tab must be closed or persistence must be disabled.';
const UNSUPPORTED_PLATFORM_ERROR_MSG =
'This platform is either missing' +
' IndexedDB or is known to have an incomplete implementation. Offline' +
' persistence has been disabled.';
/**
* An IndexedDB-backed instance of Persistence. Data is stored persistently
* across sessions.
*
* Currently the Firestore SDK only supports a single consumer of the database,
* but browsers obviously support multiple tabs. IndexedDbPersistence ensures a
* single consumer of the database via an "owner lease" stored in the database.
*
* On startup, IndexedDbPersistence assigns itself a random "ownerId" and writes
* it to a special "owner" object in the database (if no entry exists already or
* the current entry is expired). This owner lease is then verified inside every
* transaction to ensure the lease has not been lost.
*
* If a tab opts not to acquire the owner lease (because there's an existing
* non-expired owner) or loses the owner lease, IndexedDbPersistence enters a
* failed state and all subsequent operations will automatically fail.
*
* The current owner regularly refreshes the owner lease with new timestamps to
* prevent newly-opened tabs from taking over ownership.
*
* Additionally there is an optimization so that when a tab is closed, the owner
* lease is released immediately (this is especially important to make sure that
* a refreshed tab is able to immediately re-acquire the owner lease).
* Unfortunately, IndexedDB cannot be reliably used in window.unload since it is
* an asynchronous API. So in addition to attempting to give up the lease,
* the owner writes its ownerId to a "zombiedOwnerId" entry in LocalStorage
* which acts as an indicator that another tab should go ahead and take the
* owner lease immediately regardless of the current lease timestamp.
*/
export class IndexedDbPersistence implements Persistence {
/**
* The name of the main (and currently only) IndexedDB database. this name is
* appended to the prefix provided to the IndexedDbPersistence constructor.
*/
static MAIN_DATABASE = 'main';
private simpleDb: SimpleDb;
private started: boolean;
private dbName: string;
private localStoragePrefix: string;
private ownerId: string = this.generateOwnerId();
/**
* Set to an Error object if we encounter an unrecoverable error. All further
* transactions will be failed with this error.
*/
private persistenceError: Error | null;
/** The setInterval() handle tied to refreshing the owner lease. */
// tslint:disable-next-line:no-any setTimeout() type differs on browser / node
private ownerLeaseRefreshHandle: any;
/** Our window.unload handler, if registered. */
private windowUnloadHandler: (() => void) | null;
private serializer: LocalSerializer;
constructor(prefix: string, serializer: JsonProtoSerializer) {
this.dbName = prefix + IndexedDbPersistence.MAIN_DATABASE;
this.serializer = new LocalSerializer(serializer);
this.localStoragePrefix = prefix;
}
start(): Promise<void> {
Iif (!IndexedDbPersistence.isAvailable()) {
this.persistenceError = new FirestoreError(
Code.UNIMPLEMENTED,
UNSUPPORTED_PLATFORM_ERROR_MSG
);
return Promise.reject(this.persistenceError);
}
assert(!this.started, 'IndexedDbPersistence double-started!');
this.started = true;
return SimpleDb.openOrCreate(this.dbName, SCHEMA_VERSION, createOrUpgradeDb)
.then(db => {
this.simpleDb = db;
})
.then(() => this.tryAcquireOwnerLease())
.then(() => {
this.scheduleOwnerLeaseRefreshes();
this.attachWindowUnloadHook();
});
}
shutdown(): Promise<void> {
assert(this.started, 'IndexedDbPersistence shutdown without start!');
this.started = false;
this.detachWindowUnloadHook();
this.stopOwnerLeaseRefreshes();
return this.releaseOwnerLease().then(() => {
this.simpleDb.close();
});
}
getMutationQueue(user: User): MutationQueue {
return IndexedDbMutationQueue.forUser(user, this.serializer);
}
getQueryCache(): QueryCache {
return new IndexedDbQueryCache(this.serializer);
}
getRemoteDocumentCache(): RemoteDocumentCache {
return new IndexedDbRemoteDocumentCache(this.serializer);
}
runTransaction<T>(
action: string,
operation: (transaction: SimpleDbTransaction) => PersistencePromise<T>
): Promise<T> {
Iif (this.persistenceError) {
return Promise.reject(this.persistenceError);
}
log.debug(LOG_TAG, 'Starting transaction:', action);
// Do all transactions as readwrite against all object stores, since we
// are the only reader/writer.
return this.simpleDb.runTransaction('readwrite', ALL_STORES, txn => {
// Verify that we still have the owner lease as part of every transaction.
return this.ensureOwnerLease(txn).next(() => operation(txn));
});
}
static isAvailable(): boolean {
return SimpleDb.isAvailable();
}
/**
* Generates a string used as a prefix when storing data in IndexedDB and
* LocalStorage.
*/
static buildStoragePrefix(databaseInfo: DatabaseInfo): string {
// Use two different prefix formats:
//
// * firestore / persistenceKey / projectID . databaseID / ...
// * firestore / persistenceKey / projectID / ...
//
// projectIDs are DNS-compatible names and cannot contain dots
// so there's no danger of collisions.
let database = databaseInfo.databaseId.projectId;
Iif (!databaseInfo.databaseId.isDefaultDatabase) {
database += '.' + databaseInfo.databaseId.database;
}
return 'firestore/' + databaseInfo.persistenceKey + '/' + database + '/';
}
/**
* Acquires the owner lease if there's no valid owner. Else returns a rejected
* promise.
*/
private tryAcquireOwnerLease(): Promise<void> {
// NOTE: Don't use this.runTransaction, since it requires us to already
// have the lease.
return this.simpleDb.runTransaction('readwrite', [DbOwner.store], txn => {
const store = txn.store<DbOwnerKey, DbOwner>(DbOwner.store);
return store.get('owner').next(dbOwner => {
Eif (!this.validOwner(dbOwner)) {
const newDbOwner = new DbOwner(this.ownerId, Date.now());
log.debug(
LOG_TAG,
'No valid owner. Acquiring owner lease. Current owner:',
dbOwner,
'New owner:',
newDbOwner
);
return store.put('owner', newDbOwner);
} else {
log.debug(
LOG_TAG,
'Valid owner already. Failing. Current owner:',
dbOwner
);
this.persistenceError = new FirestoreError(
Code.FAILED_PRECONDITION,
EXISTING_OWNER_ERROR_MSG
);
return PersistencePromise.reject<void>(this.persistenceError);
}
});
});
}
/** Checks the owner lease and deletes it if we are the current owner. */
private releaseOwnerLease(): Promise<void> {
// NOTE: Don't use this.runTransaction, since it requires us to already
// have the lease.
return this.simpleDb.runTransaction('readwrite', [DbOwner.store], txn => {
const store = txn.store<DbOwnerKey, DbOwner>(DbOwner.store);
return store.get('owner').next(dbOwner => {
Eif (dbOwner !== null && dbOwner.ownerId === this.ownerId) {
log.debug(LOG_TAG, 'Releasing owner lease.');
return store.delete('owner');
} else {
return PersistencePromise.resolve();
}
});
});
}
/**
* Checks the owner lease and returns a rejected promise if we are not the
* current owner. This should be included in every transaction to guard
* against losing the owner lease.
*/
private ensureOwnerLease(txn: SimpleDbTransaction): PersistencePromise<void> {
const store = txn.store<DbOwnerKey, DbOwner>(DbOwner.store);
return store.get('owner').next(dbOwner => {
Iif (dbOwner === null || dbOwner.ownerId !== this.ownerId) {
this.persistenceError = new FirestoreError(
Code.FAILED_PRECONDITION,
EXISTING_OWNER_ERROR_MSG
);
return PersistencePromise.reject<void>(this.persistenceError);
} else {
return PersistencePromise.resolve();
}
});
}
/**
* Returns true if the provided owner exists, has a recent timestamp, and
* isn't zombied.
*
* NOTE: To determine if the owner is zombied, this method reads from
* LocalStorage which could be mildly expensive.
*/
private validOwner(dbOwner: DbOwner | null): boolean {
const now = Date.now();
const minAcceptable = now - OWNER_LEASE_MAX_AGE_MS;
const maxAcceptable = now;
Eif (dbOwner === null) {
return false; // no owner.
} else if (dbOwner.leaseTimestampMs < minAcceptable) {
return false; // owner lease has expired.
} else if (dbOwner.leaseTimestampMs > maxAcceptable) {
log.error(
'Persistence owner-lease is in the future. Discarding.',
dbOwner
);
return false;
} else if (dbOwner.ownerId === this.getZombiedOwnerId()) {
return false; // owner's tab closed.
} else {
return true;
}
}
/**
* Schedules a recurring timer to update the owner lease timestamp to prevent
* other tabs from taking the lease.
*/
private scheduleOwnerLeaseRefreshes(): void {
// NOTE: This doesn't need to be scheduled on the async queue and doing so
// would increase the chances of us not refreshing on time if the queue is
// backed up for some reason.
this.ownerLeaseRefreshHandle = setInterval(() => {
const txResult = this.runTransaction('Refresh owner timestamp', txn => {
// NOTE: We don't need to validate the current owner contents, since
// runTransaction does that automatically.
const store = txn.store<DbOwnerKey, DbOwner>(DbOwner.store);
return store.put('owner', new DbOwner(this.ownerId, Date.now()));
});
txResult.catch(reason => {
// Probably means we lost the lease. Report the error and stop trying to
// refresh the lease.
log.error(reason);
this.stopOwnerLeaseRefreshes();
});
}, OWNER_LEASE_REFRESH_INTERVAL_MS);
}
private stopOwnerLeaseRefreshes(): void {
Eif (this.ownerLeaseRefreshHandle) {
clearInterval(this.ownerLeaseRefreshHandle);
this.ownerLeaseRefreshHandle = null;
}
}
/**
* Attaches a window.unload handler that will synchronously write our
* ownerId to a "zombie owner id" location in localstorage. This can be used
* by tabs trying to acquire the lease to determine that the lease should be
* acquired immediately even if the timestamp is recent. This is particularly
* important for the refresh case (so the tab correctly re-acquires the owner
* lease). LocalStorage is used for this rather than IndexedDb because it is
* a synchronous API and so can be used reliably from an unload handler.
*/
private attachWindowUnloadHook(): void {
this.windowUnloadHandler = () => {
// Record that we're zombied.
this.setZombiedOwnerId(this.ownerId);
// Attempt graceful shutdown (including releasing our owner lease), but
// there's no guarantee it will complete.
this.shutdown();
};
window.addEventListener('unload', this.windowUnloadHandler);
}
private detachWindowUnloadHook(): void {
Eif (this.windowUnloadHandler) {
window.removeEventListener('unload', this.windowUnloadHandler);
this.windowUnloadHandler = null;
}
}
/**
* Returns any recorded "zombied owner" (i.e. a previous owner that became
* zombied due to their tab closing) from LocalStorage, or null if no such
* record exists.
*/
private getZombiedOwnerId(): string | null {
try {
const zombiedOwnerId = window.localStorage.getItem(
this.zombiedOwnerLocalStorageKey()
);
log.debug(LOG_TAG, 'Zombied ownerID from LocalStorage:', zombiedOwnerId);
return zombiedOwnerId;
} catch (e) {
// Gracefully handle if LocalStorage isn't available / working.
log.error('Failed to get zombie owner id.', e);
return null;
}
}
/**
* Records a zombied owner (an owner that had its tab closed) in LocalStorage
* or, if passed null, deletes any recorded zombied owner.
*/
private setZombiedOwnerId(zombieOwnerId: string | null) {
try {
if (zombieOwnerId === null) {
window.localStorage.removeItem(this.zombiedOwnerLocalStorageKey());
} else {
window.localStorage.setItem(
this.zombiedOwnerLocalStorageKey(),
zombieOwnerId
);
}
} catch (e) {
// Gracefully handle if LocalStorage isn't available / working.
log.error('Failed to set zombie owner id.', e);
}
}
private zombiedOwnerLocalStorageKey(): string {
return this.localStoragePrefix + ZOMBIE_OWNER_LOCALSTORAGE_SUFFIX;
}
private generateOwnerId(): string {
// For convenience, just use an AutoId.
return AutoId.newId();
}
}
|