use cached gallery results

related to #2621

src/vs/workbench/parts/extensions/node/vsoGalleryService.ts

@@ -8,6 +8,7 @@
 import { assign } from 'vs/base/common/objects';
 import { TPromise } from 'vs/base/common/winjs.base';
 import { IGalleryService, IExtension } from 'vs/workbench/parts/extensions/common/extensions';
+import { IXHRResponse } from 'vs/base/common/http';
 import { IRequestService } from 'vs/platform/request/common/request';
 import { IWorkspaceContextService } from 'vs/workbench/services/workspace/common/contextService';
 
@@ -50,55 +51,58 @@ function getInstallCount(statistics: IGalleryExtensionStatistics[]): number {
 	return result ? result.value : 0;
 }
 
+const FIVE_MINUTES = 1000 * 60 * 5;
+
 export class GalleryService implements IGalleryService {
 
-	public serviceId = IGalleryService;
+	serviceId = IGalleryService;
 
 	private extensionsGalleryUrl: string;
+	private extensionsCacheUrl: string;
 
 	constructor(
 		@IRequestService private requestService: IRequestService,
 		@IWorkspaceContextService contextService: IWorkspaceContextService
 	) {
-		const extensionsGalleryConfig = contextService.getConfiguration().env.extensionsGallery;
-		this.extensionsGalleryUrl = extensionsGalleryConfig && extensionsGalleryConfig.serviceUrl;
+		const config = contextService.getConfiguration().env.extensionsGallery;
+		this.extensionsGalleryUrl = config && config.serviceUrl;
+		this.extensionsCacheUrl = config && config.cacheUrl;
 	}
 
 	private api(path = ''): string {
 		return `${ this.extensionsGalleryUrl }${ path }`;
 	}
 
-	public isEnabled(): boolean {
+	isEnabled(): boolean {
 		return !!this.extensionsGalleryUrl;
 	}
 
-	public query(): TPromise<IExtension[]> {
-		if (!this.extensionsGalleryUrl) {
+	query(): TPromise<IExtension[]> {
+		if (!this.isEnabled()) {
 			return TPromise.wrapError(new Error('No extension gallery service configured.'));
 		}
 
-		const data = JSON.stringify({
-			filters: [{
-				criteria:[{
-					filterType: 1,
-					value: 'vscode'
-				}]
-			}],
-			flags: 0x1 | 0x4 | 0x80 | 0x100
-		});
+		const gallery = this.queryGallery();
+		const cache = this.queryCache().then(r => {
+			const rawLastModified = r.getResponseHeader('last-modified');
 
-		const request = {
-			type: 'POST',
-			url: this.api('/extensionquery'),
-			data: data,
-			headers: {
-				'Content-Type': 'application/json',
-				'Accept': 'application/json;api-version=3.0-preview.1',
-				'Content-Length': data.length
+			if (!rawLastModified) {
+				return gallery;
 			}
-		};
 
-		return this.requestService.makeRequest(request)
+			const lastModified = new Date(rawLastModified).getTime();
+			const now = new Date().getTime();
+			const diff = now - lastModified;
+
+			if (diff > FIVE_MINUTES) {
+				return gallery;
+			}
+
+			gallery.cancel();
+			return TPromise.as(r);
+		}, err => gallery);
+
+		return cache
 			.then<IGalleryExtension[]>(r => JSON.parse(r.responseText).results[0].extensions || [])
 			.then<IExtension[]>(extensions => {
 				return extensions.map(extension => ({
@@ -119,4 +123,34 @@ export class GalleryService implements IGalleryService {
 				}));
 			});
 	}
+
+	private queryCache(): TPromise<IXHRResponse> {
+		const url = this.extensionsCacheUrl;
+		return this.requestService.makeRequest({ url });
+	}
+
+	private queryGallery(): TPromise<IXHRResponse> {
+		const data = JSON.stringify({
+			filters: [{
+				criteria:[{
+					filterType: 1,
+					value: 'vscode'
+				}]
+			}],
+			flags: 0x1 | 0x4 | 0x80 | 0x100
+		});
+
+		const request = {
+			type: 'POST',
+			url: this.api('/extensionquery'),
+			data: data,
+			headers: {
+				'Content-Type': 'application/json',
+				'Accept': 'application/json;api-version=3.0-preview.1',
+				'Content-Length': data.length
+			}
+		};
+
+		return this.requestService.makeRequest(request);
+	}
 }
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