Add ConnectivityMonitor

packages/firestore/src/platform/platform.ts

@@ -20,6 +20,7 @@ import { ProtoByteString } from '../core/types';
 import { Connection } from '../remote/connection';
 import { JsonProtoSerializer } from '../remote/serializer';
 import { fail } from '../util/assert';
+import { ConnectivityMonitor } from './../remote/connectivity_monitor';
 
 /**
  * Provides a common interface to load anything platform dependent, e.g.
@@ -31,6 +32,7 @@ import { fail } from '../util/assert';
 // use in our client.
 export interface Platform {
   loadConnection(databaseInfo: DatabaseInfo): Promise<Connection>;
+  newConnectivityMonitor(): ConnectivityMonitor;
   newSerializer(databaseId: DatabaseId): JsonProtoSerializer;
 
   /** Formats an object as a JSON string, suitable for logging. */

packages/firestore/src/platform_browser/browser_connectivity_monitor.ts

@@ -0,0 +1,67 @@
+/**
+ * @license
+ * Copyright 2019 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 { debug } from '../util/log';
+import {
+  ConnectivityMonitor,
+  ConnectivityMonitorCallback,
+  NetworkStatus
+} from './../remote/connectivity_monitor';
+
+const LOG_TAG = 'ConnectivityMonitor';
+
+/**
+ * Browser implementation of ConnectivityMonitor.
+ */
+export class BrowserConnectivityMonitor implements ConnectivityMonitor {
+  private readonly networkAvailableListener = () => this.onNetworkAvailable();
+  private readonly networkUnavailableListener = () =>
+    this.onNetworkUnavailable();
+  private callbacks: ConnectivityMonitorCallback[] = [];
+
+  constructor() {
+    this.configureNetworkMonitoring();
+  }
+
+  addCallback(callback: (status: NetworkStatus) => void): void {
+    this.callbacks.push(callback);
+  }
+
+  shutdown(): void {
+    window.removeEventListener('online', this.networkAvailableListener);
+    window.removeEventListener('offline', this.networkUnavailableListener);
+  }
+
+  private configureNetworkMonitoring(): void {
+    window.addEventListener('online', this.networkAvailableListener);
+    window.addEventListener('offline', this.networkUnavailableListener);
+  }
+
+  private onNetworkAvailable(): void {
+    debug(LOG_TAG, 'Network connectivity changed: AVAILABLE');
+    for (const callback of this.callbacks) {
+      callback(NetworkStatus.AVAILABLE);
+    }
+  }
+
+  private onNetworkUnavailable(): void {
+    debug(LOG_TAG, 'Network connectivity changed: UNAVAILABLE');
+    for (const callback of this.callbacks) {
+      callback(NetworkStatus.UNAVAILABLE);
+    }
+  }
+}

packages/firestore/src/platform_browser/browser_platform.ts

@@ -19,7 +19,9 @@ import { DatabaseId, DatabaseInfo } from '../core/database_info';
 import { Platform } from '../platform/platform';
 import { Connection } from '../remote/connection';
 import { JsonProtoSerializer } from '../remote/serializer';
+import { ConnectivityMonitor } from './../remote/connectivity_monitor';
 
+import { BrowserConnectivityMonitor } from './browser_connectivity_monitor';
 import { WebChannelConnection } from './webchannel_connection';
 
 export class BrowserPlatform implements Platform {
@@ -43,6 +45,10 @@ export class BrowserPlatform implements Platform {
     return Promise.resolve(new WebChannelConnection(databaseInfo));
   }
 
+  newConnectivityMonitor(): ConnectivityMonitor {
+    return new BrowserConnectivityMonitor();
+  }
+
   newSerializer(databaseId: DatabaseId): JsonProtoSerializer {
     return new JsonProtoSerializer(databaseId, { useProto3Json: true });
   }

packages/firestore/src/platform_node/node_platform.ts

@@ -22,6 +22,8 @@ import { Platform } from '../platform/platform';
 import { Connection } from '../remote/connection';
 import { JsonProtoSerializer } from '../remote/serializer';
 import { Code, FirestoreError } from '../util/error';
+import { ConnectivityMonitor } from './../remote/connectivity_monitor';
+import { NoopConnectivityMonitor } from './../remote/connectivity_monitor_noop';
 
 import { GrpcConnection } from './grpc_connection';
 import { loadProtos } from './load_protos';
@@ -46,6 +48,10 @@ export class NodePlatform implements Platform {
     return Promise.resolve(new GrpcConnection(protos, databaseInfo));
   }
 
+  newConnectivityMonitor(): ConnectivityMonitor {
+    return new NoopConnectivityMonitor();
+  }
+
   newSerializer(partitionId: DatabaseId): JsonProtoSerializer {
     return new JsonProtoSerializer(partitionId, { useProto3Json: false });
   }

packages/firestore/src/remote/connectivity_monitor.ts

@@ -0,0 +1,51 @@
+/**
+ * @license
+ * Copyright 2019 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.
+ */
+
+/**
+ * The set of network states is deliberately simplified -- we only care about
+ * states such that transition between them should break currently
+ * established connections.
+ */
+export const enum NetworkStatus {
+  AVAILABLE,
+  UNAVAILABLE
+}
+
+export type ConnectivityMonitorCallback = (status: NetworkStatus) => void;
+
+/**
+ * A base class for monitoring changes in network connectivity; it is expected
+ * that each platform will have its own system-dependent implementation.
+ */
+export interface ConnectivityMonitor {
+  /**
+   * Adds a callback to be called when connectivity changes.
+   *
+   * Callbacks are not made on the initial state of connectivity, since this
+   * monitor is primarily used for resetting backoff in the remote store when
+   * connectivity changes. As such, the initial connectivity state is
+   * irrelevant here.
+   */
+  addCallback(callback: ConnectivityMonitorCallback): void;
+
+  /**
+   * Stops monitoring connectivity. After this call completes, no further
+   * callbacks will be triggered. After shutdown() is called, no further calls
+   * are allowed on this instance.
+   */
+  shutdown(): void;
+}

packages/firestore/src/remote/connectivity_monitor_noop.ts

@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright 2019 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 { ConnectivityMonitor, NetworkStatus } from './connectivity_monitor';
+
+export class NoopConnectivityMonitor implements ConnectivityMonitor {
+  addCallback(callback: (status: NetworkStatus) => void): void {
+    // No-op.
+  }
+
+  shutdown(): void {
+    // No-op.
+  }
+}

packages/firestore/test/util/test_platform.ts

@@ -21,6 +21,8 @@ import { Platform } from '../../src/platform/platform';
 import { Connection } from '../../src/remote/connection';
 import { JsonProtoSerializer } from '../../src/remote/serializer';
 import { assert, fail } from '../../src/util/assert';
+import { ConnectivityMonitor } from './../../src/remote/connectivity_monitor';
+import { NoopConnectivityMonitor } from './../../src/remote/connectivity_monitor_noop';
 
 /**
  * `Window` fake that implements the event and storage API that is used by
@@ -245,6 +247,10 @@ export class TestPlatform implements Platform {
     return this.basePlatform.loadConnection(databaseInfo);
   }
 
+  newConnectivityMonitor(): ConnectivityMonitor {
+    return new NoopConnectivityMonitor();
+  }
+
   newSerializer(databaseId: DatabaseId): JsonProtoSerializer {
     return this.basePlatform.newSerializer(databaseId);
   }