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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 * as api from '../protos/firestore_proto_api';
import { CredentialsProvider, Token } from '../api/credentials';
import { SnapshotVersion } from '../core/snapshot_version';
import { ProtoByteString, TargetId } from '../core/types';
import { QueryData } from '../local/query_data';
import { Mutation, MutationResult } from '../model/mutation';
import { assert } from '../util/assert';
import { AsyncQueue, TimerId } from '../util/async_queue';
import { Code, FirestoreError } from '../util/error';
import * as log from '../util/log';
import { ExponentialBackoff } from './backoff';
import { Connection, Stream } from './connection';
import { JsonProtoSerializer } from './serializer';
import { WatchChange } from './watch_change';
import { isNullOrUndefined } from '../util/types';
import { CancelablePromise } from '../util/promise';
const LOG_TAG = 'PersistentStream';
// The generated proto interfaces for these class are missing the database
// field. So we add it here.
// TODO(b/36015800): Remove this once the api generator is fixed.
interface ListenRequest extends api.ListenRequest {
database?: string;
}
export interface WriteRequest extends api.WriteRequest {
database?: string;
}
enum PersistentStreamState {
/**
* The streaming RPC is not running and there's no error condition.
* Calling `start` will start the stream immediately without backoff.
* While in this state isStarted will return false.
*/
Initial,
/**
* The stream is starting, and is waiting for an auth token to attach to
* the initial request. While in this state, isStarted will return
* true but isOpen will return false.
*/
Auth,
/**
* The streaming RPC is up and running. Requests and responses can flow
* freely. Both isStarted and isOpen will return true.
*/
Open,
/**
* The stream encountered an error. The next start attempt will back off.
* While in this state isStarted() will return false.
*
*/
Error,
/**
* An in-between state after an error where the stream is waiting before
* re-starting. After
* waiting is complete, the stream will try to open. While in this
* state isStarted() will return YES but isOpen will return false.
*/
Backoff,
/**
* The stream has been explicitly stopped; no further events will be emitted.
*/
Stopped
}
/**
* Provides a common interface that is shared by the listeners for stream
* events by the concrete implementation classes.
*/
export interface PersistentStreamListener {
/**
* Called after the stream was established and can accept outgoing
* messages
*/
onOpen: () => Promise<void>;
/**
* Called after the stream has closed. If there was an error, the
* FirestoreError will be set.
*/
onClose: (err?: FirestoreError) => Promise<void>;
}
/**
* Initial backoff time in milliseconds after an error.
* Set to 1s according to https://cloud.google.com/apis/design/errors.
*/
const BACKOFF_INITIAL_DELAY_MS = 1000;
/** Maximum backoff time in milliseconds */
const BACKOFF_MAX_DELAY_MS = 60 * 1000;
const BACKOFF_FACTOR = 1.5;
/** The time a stream stays open after it is marked idle. */
const IDLE_TIMEOUT_MS = 60 * 1000;
/**
* A PersistentStream is an abstract base class that represents a streaming RPC
* to the Firestore backend. It's built on top of the connections own support
* for streaming RPCs, and adds several critical features for our clients:
*
* - Exponential backoff on failure
* - Authentication via CredentialsProvider
* - Dispatching all callbacks into the shared worker queue
*
* Subclasses of PersistentStream implement serialization of models to and
* from the JSON representation of the protocol buffers for a specific
* streaming RPC.
*
* ## Starting and Stopping
*
* Streaming RPCs are stateful and need to be `start`ed before messages can
* be sent and received. The PersistentStream will call the onOpen function
* of the listener once the stream is ready to accept requests.
*
* Should a `start` fail, PersistentStream will call the registered
* onClose with a FirestoreError indicating what went wrong.
*
* A PersistentStream can be started and stopped repeatedly.
*
* Generic types:
* SendType: The type of the outgoing message of the underlying
* connection stream
* ReceiveType: The type of the incoming message of the underlying
* connection stream
* ListenerType: The type of the listener that will be used for callbacks
*/
export abstract class PersistentStream<
SendType,
ReceiveType,
ListenerType extends PersistentStreamListener
> {
private state: PersistentStreamState;
private inactivityTimerPromise: CancelablePromise<void> | null = null;
private stream: Stream<SendType, ReceiveType> | null = null;
protected backoff: ExponentialBackoff;
protected listener: ListenerType | null = null;
constructor(
private queue: AsyncQueue,
connectionTimerId: TimerId,
private idleTimerId: TimerId,
protected connection: Connection,
private credentialsProvider: CredentialsProvider
) {
this.backoff = new ExponentialBackoff(
queue,
connectionTimerId,
BACKOFF_INITIAL_DELAY_MS,
BACKOFF_FACTOR,
BACKOFF_MAX_DELAY_MS
);
this.state = PersistentStreamState.Initial;
}
/**
* Returns true if `start` has been called and no error has occurred. True
* indicates the stream is open or in the process of opening (which
* encompasses respecting backoff, getting auth tokens, and starting the
* actual RPC). Use `isOpen` to determine if the stream is open and ready for
* outbound requests.
*/
isStarted(): boolean {
return (
this.state === PersistentStreamState.Backoff ||
this.state === PersistentStreamState.Auth ||
this.state === PersistentStreamState.Open
);
}
/**
* Returns true if the underlying RPC is open (the openHandler has been
* called) and the stream is ready for outbound requests.
*/
isOpen(): boolean {
return this.state === PersistentStreamState.Open;
}
/**
* Starts the RPC. Only allowed if isStarted returns false. The stream is
* not immediately ready for use: onOpen will be invoked when the RPC is ready
* for outbound requests, at which point isOpen will return true.
*
* When start returns, isStarted will return true.
*/
start(listener: ListenerType): void {
if (this.state === PersistentStreamState.Error) {
this.performBackoff(listener);
return;
}
assert(this.state === PersistentStreamState.Initial, 'Already started');
this.listener = listener;
this.auth();
}
/**
* Stops the RPC. This call is idempotent and allowed regardless of the
* current isStarted state.
*
* When stop returns, isStarted and isOpen will both return false.
*/
stop(): void {
if (this.isStarted()) {
this.close(PersistentStreamState.Stopped);
}
}
/**
* After an error the stream will usually back off on the next attempt to
* start it. If the error warrants an immediate restart of the stream, the
* sender can use this to indicate that the receiver should not back off.
*
* Each error will call the onClose function. That function can decide to
* inhibit backoff if required.
*/
inhibitBackoff(): void {
assert(!this.isStarted(), 'Can only inhibit backoff in a stopped state');
this.state = PersistentStreamState.Initial;
this.backoff.reset();
}
/**
* Marks this stream as idle. If no further actions are performed on the
* stream for one minute, the stream will automatically close itself and
* notify the stream's onClose() handler with Status.OK. The stream will then
* be in a !isStarted() state, requiring the caller to start the stream again
* before further use.
*
* Only streams that are in state 'Open' can be marked idle, as all other
* states imply pending network operations.
*/
markIdle(): void {
// Starts the idle time if we are in state 'Open' and are not yet already
// running a timer (in which case the previous idle timeout still applies).
if (this.isOpen() && this.inactivityTimerPromise === null) {
this.inactivityTimerPromise = this.queue.enqueueAfterDelay(
this.idleTimerId,
IDLE_TIMEOUT_MS,
() => this.handleIdleCloseTimer()
);
this.inactivityTimerPromise.catch((err: FirestoreError) => {
// When the AsyncQueue gets drained during testing, pending Promises
// (including these idle checks) will get rejected. We special-case
// these cancelled idle checks to make sure that these specific Promise
// rejections are not considered unhandled.
assert(
err.code === Code.CANCELLED,
`Received unexpected error in idle timeout closure. Expected CANCELLED, but was: ${
err
}`
);
});
}
}
/** Sends a message to the underlying stream. */
protected sendRequest(msg: SendType): void {
this.cancelIdleCheck();
this.stream!.send(msg);
}
/** Called by the idle timer when the stream should close due to inactivity. */
private handleIdleCloseTimer(): Promise<void> {
Eif (this.isOpen()) {
// When timing out an idle stream there's no reason to force the stream into backoff when
// it restarts so set the stream state to Initial instead of Error.
return this.close(PersistentStreamState.Initial);
}
return Promise.resolve();
}
/** Marks the stream as active again. */
private cancelIdleCheck() {
if (this.inactivityTimerPromise) {
this.inactivityTimerPromise.cancel();
this.inactivityTimerPromise = null;
}
}
/**
* Closes the stream and cleans up as necessary:
*
* * closes the underlying GRPC stream;
* * calls the onClose handler with the given 'error';
* * sets internal stream state to 'finalState';
* * adjusts the backoff timer based on the error
*
* A new stream can be opened by calling `start` unless `finalState` is set to
* `PersistentStreamState.Stopped`.
*
* @param finalState the intended state of the stream after closing.
* @param error the error the connection was closed with.
*/
private close(
finalState: PersistentStreamState,
error?: FirestoreError
): Promise<void> {
assert(
finalState === PersistentStreamState.Error || isNullOrUndefined(error),
"Can't provide an error when not in an error state."
);
this.cancelIdleCheck();
if (finalState !== PersistentStreamState.Error) {
// If this is an intentional close ensure we don't delay our next connection attempt.
this.backoff.reset();
} else if (error && error.code === Code.RESOURCE_EXHAUSTED) {
// Log the error. (Probably either 'quota exceeded' or 'max queue length reached'.)
log.error(error.toString());
log.error(
'Using maximum backoff delay to prevent overloading the backend.'
);
this.backoff.resetToMax();
}
// Clean up the underlying stream because we are no longer interested in events.
if (this.stream !== null) {
this.tearDown();
this.stream.close();
this.stream = null;
}
// This state must be assigned before calling onClose() to allow the callback to
// inhibit backoff or otherwise manipulate the state in its non-started state.
this.state = finalState;
const listener = this.listener!;
// Clear the listener to avoid bleeding of events from the underlying streams.
this.listener = null;
// If the caller explicitly requested a stream stop, don't notify them of a closing stream (it
// could trigger undesirable recovery logic, etc.).
if (finalState !== PersistentStreamState.Stopped) {
return listener.onClose(error);
} else {
return Promise.resolve();
}
}
/**
* Can be overridden to perform additional cleanup before the stream is closed.
* Calling super.tearDown() is not required.
*/
protected tearDown(): void {}
/**
* Used by subclasses to start the concrete RPC and return the underlying
* connection stream.
*/
protected abstract startRpc(
token: Token | null
): Stream<SendType, ReceiveType>;
/**
* Called after the stream has received a message. The function will be
* called on the right queue and must return a Promise.
* @param message The message received from the stream.
*/
protected abstract onMessage(message: ReceiveType): Promise<void>;
private auth(): void {
assert(
this.state === PersistentStreamState.Initial,
'Must be in initial state to auth'
);
this.state = PersistentStreamState.Auth;
this.credentialsProvider.getToken(/*forceRefresh=*/ false).then(
token => {
// Normally we'd have to schedule the callback on the AsyncQueue.
// However, the following calls are safe to be called outside the
// AsyncQueue since they don't chain asynchronous calls
this.startStream(token);
},
(error: Error) => {
this.queue.enqueue(() => {
if (this.state !== PersistentStreamState.Stopped) {
// Stream can be stopped while waiting for authorization.
const rpcError = new FirestoreError(
Code.UNKNOWN,
'Fetching auth token failed: ' + error.message
);
return this.handleStreamClose(rpcError);
} else {
return Promise.resolve();
}
});
}
);
}
private startStream(token: Token | null): void {
Iif (this.state === PersistentStreamState.Stopped) {
// Stream can be stopped while waiting for authorization.
return;
}
assert(
this.state === PersistentStreamState.Auth,
'Trying to start stream in a non-auth state'
);
// Helper function to dispatch to AsyncQueue and make sure that any
// close will seem instantaneous and events are prevented from being
// raised after the close call
const dispatchIfStillActive = (
stream: Stream<SendType, ReceiveType>,
fn: () => Promise<void>
) => {
this.queue.enqueue(() => {
// Only raise events if the stream instance has not changed
if (this.stream === stream) {
return fn();
} else {
return Promise.resolve();
}
});
};
// Only start stream if listener has not changed
Eif (this.listener !== null) {
const currentStream = this.startRpc(token);
this.stream = currentStream;
this.stream.onOpen(() => {
dispatchIfStillActive(currentStream, () => {
assert(
this.state === PersistentStreamState.Auth,
'Expected stream to be in state auth, but was ' + this.state
);
this.state = PersistentStreamState.Open;
return this.listener!.onOpen();
});
});
this.stream.onClose((error: FirestoreError) => {
dispatchIfStillActive(currentStream, () => {
return this.handleStreamClose(error);
});
});
this.stream.onMessage((msg: ReceiveType) => {
dispatchIfStillActive(currentStream, () => {
return this.onMessage(msg);
});
});
}
}
private performBackoff(listener: ListenerType): void {
assert(
this.state === PersistentStreamState.Error,
'Should only perform backoff in an error case'
);
this.state = PersistentStreamState.Backoff;
this.backoff.backoffAndRun(() => {
if (this.state === PersistentStreamState.Stopped) {
// Stream can be stopped while waiting for backoff to complete.
return Promise.resolve();
}
this.state = PersistentStreamState.Initial;
this.start(listener);
assert(this.isStarted(), 'PersistentStream should have started');
return Promise.resolve();
});
}
private handleStreamClose(error?: FirestoreError): Promise<void> {
assert(this.isStarted(), "Can't handle server close on non-started stream");
log.debug(LOG_TAG, `close with error: ${error}`);
this.stream = null;
// In theory the stream could close cleanly, however, in our current model
// we never expect this to happen because if we stop a stream ourselves,
// this callback will never be called. To prevent cases where we retry
// without a backoff accidentally, we set the stream to error in all cases.
return this.close(PersistentStreamState.Error, error);
}
}
/** Listener for the PersistentWatchStream */
export interface WatchStreamListener extends PersistentStreamListener {
/**
* Called on a watchChange. The snapshot parameter will be MIN if the watch
* change did not have a snapshot associated with it.
*/
onWatchChange: (
watchChange: WatchChange,
snapshot: SnapshotVersion
) => Promise<void>;
}
/**
* A PersistentStream that implements the Listen RPC.
*
* Once the Listen stream has called the openHandler, any number of listen and
* unlisten calls calls can be sent to control what changes will be sent from
* the server for ListenResponses.
*/
export class PersistentListenStream extends PersistentStream<
api.ListenRequest,
api.ListenResponse,
WatchStreamListener
> {
constructor(
queue: AsyncQueue,
connection: Connection,
credentials: CredentialsProvider,
private serializer: JsonProtoSerializer
) {
super(
queue,
TimerId.ListenStreamConnection,
TimerId.ListenStreamIdle,
connection,
credentials
);
}
protected startRpc(
token: Token | null
): Stream<api.ListenRequest, api.ListenResponse> {
return this.connection.openStream<api.ListenRequest, api.ListenResponse>(
'Listen',
token
);
}
protected onMessage(watchChangeProto: api.ListenResponse): Promise<void> {
// A successful response means the stream is healthy
this.backoff.reset();
const watchChange = this.serializer.fromWatchChange(watchChangeProto);
const snapshot = this.serializer.versionFromListenResponse(
watchChangeProto
);
return this.listener!.onWatchChange(watchChange, snapshot);
}
/**
* Registers interest in the results of the given query. If the query
* includes a resumeToken it will be included in the request. Results that
* affect the query will be streamed back as WatchChange messages that
* reference the targetId.
*/
watch(queryData: QueryData): void {
const request: ListenRequest = {};
request.database = this.serializer.encodedDatabaseId;
request.addTarget = this.serializer.toTarget(queryData);
const labels = this.serializer.toListenRequestLabels(queryData);
if (labels) {
request.labels = labels;
}
this.sendRequest(request);
}
/**
* Unregisters interest in the results of the query associated with the
* given targetId.
*/
unwatch(targetId: TargetId): void {
const request: ListenRequest = {};
request.database = this.serializer.encodedDatabaseId;
request.removeTarget = targetId;
this.sendRequest(request);
}
}
/** Listener for the PersistentWriteStream */
export interface WriteStreamListener extends PersistentStreamListener {
/**
* Called by the PersistentWriteStream upon a successful handshake response
* from the server, which is the receiver's cue to send any pending writes.
*/
onHandshakeComplete: () => Promise<void>;
/**
* Called by the PersistentWriteStream upon receiving a StreamingWriteResponse
* from the server that contains a mutation result.
*/
onMutationResult: (
commitVersion: SnapshotVersion,
results: MutationResult[]
) => Promise<void>;
}
/**
* A Stream that implements the Write RPC.
*
* The Write RPC requires the caller to maintain special streamToken
* state in between calls, to help the server understand which responses the
* client has processed by the time the next request is made. Every response
* will contain a streamToken; this value must be passed to the next
* request.
*
* After calling start() on this stream, the next request must be a handshake,
* containing whatever streamToken is on hand. Once a response to this
* request is received, all pending mutations may be submitted. When
* submitting multiple batches of mutations at the same time, it's
* okay to use the same streamToken for the calls to writeMutations.
*
* TODO(b/33271235): Use proto types
*/
export class PersistentWriteStream extends PersistentStream<
api.WriteRequest,
api.WriteResponse,
WriteStreamListener
> {
private handshakeComplete_ = false;
constructor(
queue: AsyncQueue,
connection: Connection,
credentials: CredentialsProvider,
private serializer: JsonProtoSerializer
) {
super(
queue,
TimerId.WriteStreamConnection,
TimerId.WriteStreamIdle,
connection,
credentials
);
}
/**
* The last received stream token from the server, used to acknowledge which
* responses the client has processed. Stream tokens are opaque checkpoint
* markers whose only real value is their inclusion in the next request.
*
* PersistentWriteStream manages propagating this value from responses to the
* next request.
*/
lastStreamToken: ProtoByteString;
/**
* Tracks whether or not a handshake has been successfully exchanged and
* the stream is ready to accept mutations.
*/
get handshakeComplete(): boolean {
return this.handshakeComplete_;
}
// Override of PersistentStream.start
start(listener: WriteStreamListener): void {
this.handshakeComplete_ = false;
super.start(listener);
}
protected tearDown() {
if (this.handshakeComplete_) {
this.writeMutations([]);
}
}
protected startRpc(
token: Token | null
): Stream<api.WriteRequest, api.WriteResponse> {
return this.connection.openStream<api.WriteRequest, api.WriteResponse>(
'Write',
token
);
}
protected onMessage(responseProto: api.WriteResponse): Promise<void> {
// Always capture the last stream token.
assert(
!!responseProto.streamToken,
'Got a write response without a stream token'
);
this.lastStreamToken = responseProto.streamToken!;
if (!this.handshakeComplete_) {
// The first response is always the handshake response
assert(
!responseProto.writeResults || responseProto.writeResults.length === 0,
'Got mutation results for handshake'
);
this.handshakeComplete_ = true;
return this.listener!.onHandshakeComplete();
} else {
// A successful first write response means the stream is healthy,
// Note, that we could consider a successful handshake healthy, however,
// the write itself might be causing an error we want to back off from.
this.backoff.reset();
const results = this.serializer.fromWriteResults(
responseProto.writeResults
);
const commitVersion = this.serializer.fromVersion(
responseProto.commitTime!
);
return this.listener!.onMutationResult(commitVersion, results);
}
}
/**
* Sends an initial streamToken to the server, performing the handshake
* required to make the StreamingWrite RPC work. Subsequent
* calls should wait until onHandshakeComplete was called.
*/
writeHandshake(): void {
assert(this.isOpen(), 'Writing handshake requires an opened stream');
assert(!this.handshakeComplete_, 'Handshake already completed');
// TODO(dimond): Support stream resumption. We intentionally do not set the
// stream token on the handshake, ignoring any stream token we might have.
const request: WriteRequest = {};
request.database = this.serializer.encodedDatabaseId;
this.sendRequest(request);
}
/** Sends a group of mutations to the Firestore backend to apply. */
writeMutations(mutations: Mutation[]): void {
assert(this.isOpen(), 'Writing mutations requires an opened stream');
assert(
this.handshakeComplete_,
'Handshake must be complete before writing mutations'
);
assert(
this.lastStreamToken.length > 0,
'Trying to write mutation without a token'
);
const request: WriteRequest = {
// Protos are typed with string, but we support UInt8Array on Node
// tslint:disable-next-line:no-any
streamToken: this.lastStreamToken as any,
writes: mutations.map(mutation => this.serializer.toMutation(mutation))
};
this.sendRequest(request);
}
}
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