Reduce number of calls to /api/configuration.

src/app/app.component.ts

@@ -64,7 +64,7 @@ export class AppComponent implements OnInit, OnDestroy {
     }
 
     private checkForApplicationVersion(): Observable<Configuration> {
-        return from(this.configService.load());
+        return from(this.configService.reload());
     }
 
     private isNewVersionAvailable(version: string): boolean {

src/app/core/services/analytics.service.ts

@@ -25,7 +25,7 @@ export class AnalyticsService {
     }
 
     public init(): Observable<void> {
-        return this.configService.load().pipe(
+        return this.configService.configuration$().pipe(
             map(config => {
                 const analytics = config.analytics;
                 const {enabled, url, siteId} = analytics;

src/app/core/services/authentication.service.ts

@@ -84,7 +84,7 @@ export class AuthenticationService {
     public init(): Observable<void> {
         this._removeCookie();
 
-        return this._configService.load().pipe(
+        return this._configService.configuration$().pipe(
             map(config => ({
                 ...config.login,
                 redirectUri: `${window.location.origin}/home`,

src/app/core/services/config.service.ts

@@ -2,35 +2,48 @@ import {HttpClient} from '@angular/common/http';
 import {Injectable} from '@angular/core';
 import {environment} from 'environments/environment';
 import {Configuration} from '../models';
-import {Observable, throwError} from "rxjs";
+import {Observable, of, throwError} from "rxjs";
 import {catchError, map} from "rxjs/operators";
 import {Response} from "./visa-response";
 
 export function configServiceInitializerFactory(configurationService: ConfigService): () => Observable<Configuration> {
-    // a lambda is required here, otherwise `this` won't work inside ConfigurationService::load
-    return () => configurationService.load();
+    return () => configurationService.configuration$();
 }
 
 @Injectable()
 export class ConfigService {
+    private _configuration: Configuration;
 
     constructor(private http: HttpClient) {
     }
 
-    // the return value (Promise) of this method is used as an APP_INITIALIZER,
-    // so the application's initialization will not complete until the Promise resolves.
-    public load(): Observable<Configuration> {
+    configuration$(): Observable<Configuration> {
+        if (this._configuration != null) {
+            return of(this._configuration);
+        } else {
+            return this._load();
+        }
+    }
+
+    reload(): Observable<Configuration> {
+        this._configuration = null;
+        return this.configuration$();
+    }
+
+
+    private _load(): Observable<Configuration> {
         const configurationUrl = `${environment.paths.api}/configuration`;
 
         return this.http.get<Response<Configuration>>(configurationUrl)
             .pipe(
                 map(({data}) => {
+                    this._configuration = data;
                     return data;
                 }),
                 catchError(error => {
                     console.error(`error loading configuration: ${JSON.stringify(error)}`);
                     return throwError(error);
-                })
+                }),
             );
     }
 }

src/app/documentation/documentation.component.ts

@@ -58,7 +58,7 @@ export class DocumentationComponent implements OnInit, OnDestroy {
         this.titleService.setTitle(title);
         this.analyticsService.trackPageView(title);
 
-        this.configService.load()
+        this.configService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((config) => {
                 this._contactEmail = config.contactEmail;

src/app/shared/components/dialogs/invalid-account/dialog.component.ts

@@ -24,7 +24,7 @@ export class InvalidAccountDialogComponent implements OnInit, OnDestroy {
     }
 
     public ngOnInit(): void {
-        this._configService.load()
+        this._configService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((config) => {
                 this._contactEmail = config.contactEmail;

src/app/shared/components/login/login.component.ts

@@ -32,7 +32,7 @@ export class LoginComponent implements OnInit, OnDestroy {
     }
 
     public ngOnInit(): void {
-        this._configService.load()
+        this._configService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((config) => {
                 this.config = config;

src/app/user/home/home.component.ts

@@ -122,7 +122,7 @@ export class HomeComponent implements OnInit, OnDestroy {
             this._user = user;
         });
 
-        this.configService.load()
+        this.configService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((configuration) => {
                 this._configuration = configuration;

src/app/user/instance-new/instance-keyboard-layout-select.component.ts

@@ -60,7 +60,7 @@ export class InstanceKeyboardLayoutSelectComponent implements OnInit, OnDestroy
     }
 
     ngOnInit(): void {
-        this._configurationService.load()
+        this._configurationService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((config) => {
                 this._layouts = config.desktop.keyboardLayouts;

src/app/user/instance-new/instance-new.component.ts

@@ -175,7 +175,7 @@ export class InstanceNewComponent implements OnInit, OnDestroy, AfterViewChecked
             this._user = user;
         });
 
-        this.configurationService.load()
+        this.configurationService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((config) => {
                 this._openDataIncluded = config.experiments.openDataIncluded;

src/app/user/instance/instance.component.ts

@@ -411,7 +411,7 @@ export class InstanceComponent implements OnInit, OnDestroy {
 
     private handleClipboardData(): void {
         this.readAsyncClipboard();
-        this.configurationService.load()
+        this.configurationService.configuration$()
             .pipe(takeUntil(this._destroy$))
             .subscribe((configuration) => {
                 const isValidUri = (url) => {