WIP

Author: rafikhan

packages/firebase/index.d.ts

@@ -7735,15 +7735,27 @@ declare namespace firebase.firestore {
      * buffer traffic indefinitely. Use of this option will cause some
      * performance degradation though.
      *
-     * This setting may be removed in a future release. If you find yourself
-     * using it to work around a specific network reliability issue, please
-     * tell us about it in
-     * https://github.com/firebase/firebase-js-sdk/issues/1674.
+     * This setting cannot be used with experimentalAutodetectLongPolling and
+     * may be removed in a future release. If you find yourself using it to
+     * work around a specific network reliability issue, please tell us about
+     * it in https://github.com/firebase/firebase-js-sdk/issues/1674.
      *
      * @webonly
      */
     experimentalForceLongPolling?: boolean;
 
+    /**
+     * Configures the SDK's underlying transport (WebChannel) to automatically detect if
+     * long-polling should be used and also update as the networking conditions change. This is
+     * very similar to experimentalForceLongPolling but does automatic detection.
+     *
+     * This setting cannot be used with experimentalForceLongPolling and may be removed in a future
+     * release.
+     *
+     * @webonly
+     */
+    experimentalAutodetectLongPolling?: boolean;
+
     /**
      * Whether to skip nested properties that are set to `undefined` during
      * object serialization. If set to `true`, these properties are skipped

packages/firestore-types/index.d.ts

@@ -29,6 +29,7 @@ export interface Settings {
   timestampsInSnapshots?: boolean;
   cacheSizeBytes?: number;
   experimentalForceLongPolling?: boolean;
+  experimentalAutodetectLongPolling?: boolean;
   ignoreUndefinedProperties?: boolean;
 }
 

packages/firestore/lite/src/api/database.ts

@@ -42,6 +42,7 @@ import { Settings } from '../../';
 export const DEFAULT_HOST = 'firestore.googleapis.com';
 export const DEFAULT_SSL = true;
 export const DEFAULT_FORCE_LONG_POLLING = false; // Used by full SDK
+export const DEFAULT_AUTODETECT_LONG_POLLING = false; // Used by full SDK
 
 /**
  * The root reference to the Firestore Lite database.
@@ -107,7 +108,8 @@ export class Firestore
       /* persistenceKey= */ 'unsupported',
       host ?? DEFAULT_HOST,
       ssl ?? DEFAULT_SSL,
-      DEFAULT_FORCE_LONG_POLLING
+      DEFAULT_FORCE_LONG_POLLING,
+      DEFAULT_AUTODETECT_LONG_POLLING
     );
   }
 

packages/firestore/src/api/database.ts

@@ -67,7 +67,8 @@ import {
   validateOptionNames,
   validatePositiveNumber,
   validateStringEnum,
-  valueDescription
+  valueDescription,
+  validateIsNotUsedTogether
 } from '../util/input_validation';
 import { getLogLevel, logError, LogLevel, setLogLevel } from '../util/log';
 import { AutoId } from '../util/misc';
@@ -108,6 +109,7 @@ const DEFAULT_HOST = 'firestore.googleapis.com';
 const DEFAULT_SSL = true;
 const DEFAULT_TIMESTAMPS_IN_SNAPSHOTS = true;
 const DEFAULT_FORCE_LONG_POLLING = false;
+const DEFAULT_FORCE_AUTODETECT_LONG_POLLING = false;
 const DEFAULT_IGNORE_UNDEFINED_PROPERTIES = false;
 
 /**
@@ -153,6 +155,8 @@ class FirestoreSettings {
 
   readonly forceLongPolling: boolean;
 
+  readonly autodetectLongPolling: boolean;
+
   readonly ignoreUndefinedProperties: boolean;
 
   // Can be a google-auth-library or gapi client.
@@ -183,6 +187,7 @@ class FirestoreSettings {
       'timestampsInSnapshots',
       'cacheSizeBytes',
       'experimentalForceLongPolling',
+      'experimentalAutodetectLongPolling',
       'ignoreUndefinedProperties'
     ]);
 
@@ -256,6 +261,23 @@ class FirestoreSettings {
     );
     this.forceLongPolling =
       settings.experimentalForceLongPolling ?? DEFAULT_FORCE_LONG_POLLING;
+
+    validateNamedOptionalType(
+      'settings',
+      'boolean',
+      'experimentalAutodetectLongPolling',
+      settings.experimentalAutodetectLongPolling
+    );
+    this.autodetectLongPolling =
+      settings.experimentalAutodetectLongPolling ??
+      DEFAULT_FORCE_AUTODETECT_LONG_POLLING;
+
+    validateIsNotUsedTogether(
+      'experimentalForceLongPolling',
+      settings.experimentalForceLongPolling,
+      'experimentalAutodetectLongPolling',
+      settings.experimentalAutodetectLongPolling
+    );
   }
 
   isEqual(other: FirestoreSettings): boolean {
@@ -266,6 +288,7 @@ class FirestoreSettings {
       this.credentials === other.credentials &&
       this.cacheSizeBytes === other.cacheSizeBytes &&
       this.forceLongPolling === other.forceLongPolling &&
+      this.autodetectLongPolling === other.autodetectLongPolling &&
       this.ignoreUndefinedProperties === other.ignoreUndefinedProperties
     );
   }
@@ -501,7 +524,8 @@ export class Firestore implements firestore.FirebaseFirestore, FirebaseService {
       this._persistenceKey,
       this._settings.host,
       this._settings.ssl,
-      this._settings.forceLongPolling
+      this._settings.forceLongPolling,
+      this._settings.autodetectLongPolling
     );
   }
 

packages/firestore/src/core/database_info.ts

@@ -29,13 +29,15 @@ export class DatabaseInfo {
    * @param ssl Whether to use SSL when connecting.
    * @param forceLongPolling Whether to use the forceLongPolling option
    * when using WebChannel as the network transport.
+   * @param autodetectLongPolling TODO
    */
   constructor(
     readonly databaseId: DatabaseId,
     readonly persistenceKey: string,
     readonly host: string,
     readonly ssl: boolean,
-    readonly forceLongPolling: boolean
+    readonly forceLongPolling: boolean,
+    readonly autodetectLongPolling: boolean
   ) {}
 }
 

packages/firestore/src/platform/browser/webchannel_connection.ts

@@ -74,12 +74,14 @@ export class WebChannelConnection implements Connection {
   private readonly databaseId: DatabaseId;
   private readonly baseUrl: string;
   private readonly forceLongPolling: boolean;
+  private readonly autodetectLongPolling: boolean;
 
   constructor(info: DatabaseInfo) {
     this.databaseId = info.databaseId;
     const proto = info.ssl ? 'https' : 'http';
     this.baseUrl = proto + '://' + info.host;
     this.forceLongPolling = info.forceLongPolling;
+    this.autodetectLongPolling = info.autodetectLongPolling;
   }
 
   /**
@@ -248,7 +250,8 @@ export class WebChannelConnection implements Connection {
         // timeouts to kick in if the request isn't working.
         forwardChannelRequestTimeoutMs: 10 * 60 * 1000
       },
-      forceLongPolling: this.forceLongPolling
+      forceLongPolling: this.forceLongPolling,
+      detectBufferingProxy: this.autodetectLongPolling
     };
 
     this.modifyHeadersForRequest(request.initMessageHeaders!, token);

packages/firestore/src/util/input_validation.ts

@@ -199,6 +199,27 @@ export function validateNamedOptionalType(
   }
 }
 
+/**
+ * Validates that two boolean options are not set at the same time.
+ */
+export function validateIsNotUsedTogether(
+  optionName1: string,
+  argument1: boolean | undefined,
+  optionName2: string,
+  argument2: boolean | undefined
+): void {
+  if (
+    argument1 !== undefined &&
+    argument2 !== undefined &&
+    argument1 === argument2
+  ) {
+    throw new FirestoreError(
+      Code.INVALID_ARGUMENT,
+      `${optionName1} and ${optionName2} can not be used together.`
+    );
+  }
+}
+
 export function validateArrayElements<T>(
   functionName: string,
   optionName: string,

packages/firestore/test/integration/util/internal_helpers.ts

@@ -44,7 +44,8 @@ export function getDefaultDatabaseInfo(): DatabaseInfo {
     'persistenceKey',
     DEFAULT_SETTINGS.host!,
     !!DEFAULT_SETTINGS.ssl,
-    !!DEFAULT_SETTINGS.experimentalForceLongPolling
+    !!DEFAULT_SETTINGS.experimentalForceLongPolling,
+    /*experimentalAutodetectLongPolling=*/ true
   );
 }
 

packages/firestore/test/unit/specs/spec_test_runner.ts

@@ -206,7 +206,8 @@ abstract class TestRunner {
       TEST_PERSISTENCE_KEY,
       'host',
       /*ssl=*/ false,
-      /*forceLongPolling=*/ false
+      /*forceLongPolling=*/ false,
+      /*autodetectLongPolling=*/ true
     );
 
     // TODO(mrschmidt): During client startup in `firestore_client`, we block

packages/webchannel-wrapper/src/index.d.ts

@@ -89,6 +89,7 @@ export interface WebChannelOptions {
   httpSessionIdParam?: string;
   httpHeadersOverwriteParam?: string;
   forceLongPolling?: boolean;
+  detectBufferingProxy?: boolean;
   fastHandshake?: boolean;
   disableRedac?: boolean;
   clientProfile?: string;