fix issue where more than one api call was made on every route change

src/app/core/data/request.service.spec.ts

@@ -638,4 +638,41 @@ describe('RequestService', () => {
       expect(done$).toBeObservable(cold('-----(t|)', { t: true }));
     }));
   });
+
+  describe('setStaleByHref', () => {
+    const uuid = 'c574a42c-4818-47ac-bbe1-6c3cd622c81f';
+    const href = 'https://rest.api/some/object';
+    const freshRE: any = {
+      request: { uuid, href },
+      state: RequestEntryState.Success
+    };
+    const staleRE: any = {
+      request: { uuid, href },
+      state: RequestEntryState.SuccessStale
+    };
+
+    it(`should call getByHref to retrieve the RequestEntry matching the href`, () => {
+      spyOn(service, 'getByHref').and.returnValue(observableOf(staleRE));
+      service.setStaleByHref(href);
+      expect(service.getByHref).toHaveBeenCalledWith(href);
+    });
+
+    it(`should dispatch a RequestStaleAction for the RequestEntry returned by getByHref`, (done: DoneFn) => {
+      spyOn(service, 'getByHref').and.returnValue(observableOf(staleRE));
+      spyOn(store, 'dispatch');
+      service.setStaleByHref(href).subscribe(() => {
+        expect(store.dispatch).toHaveBeenCalledWith(new RequestStaleAction(uuid));
+        done();
+      });
+    });
+
+   it(`should emit true when the request in the store is stale`, () => {
+     spyOn(service, 'getByHref').and.returnValue(cold('a-b', {
+       a: freshRE,
+       b: staleRE
+     }));
+     const result$ = service.setStaleByHref(href);
+     expect(result$).toBeObservable(cold('--(c|)', { c: true }));
+   });
+  });
 });

src/app/core/data/request.service.ts

@@ -16,7 +16,7 @@ import {
   RequestExecuteAction,
   RequestStaleAction
 } from './request.actions';
-import { GetRequest} from './request.models';
+import { GetRequest } from './request.models';
 import { CommitSSBAction } from '../cache/server-sync-buffer.actions';
 import { RestRequestMethod } from './rest-request-method';
 import { coreSelector } from '../core.selectors';
@@ -331,7 +331,29 @@ export class RequestService {
       map((request: RequestEntry) => isStale(request.state)),
       filter((stale: boolean) => stale),
       take(1),
-      );
+    );
+  }
+
+  /**
+   * Mark a request as stale
+   * @param href  the href of the request
+   * @return      an Observable that will emit true once the Request becomes stale
+   */
+  setStaleByHref(href: string): Observable<boolean> {
+    const requestEntry$ = this.getByHref(href);
+
+    requestEntry$.pipe(
+      map((re: RequestEntry) => re.request.uuid),
+      take(1),
+    ).subscribe((uuid: string) => {
+      this.store.dispatch(new RequestStaleAction(uuid));
+    });
+
+    return requestEntry$.pipe(
+      map((request: RequestEntry) => isStale(request.state)),
+      filter((stale: boolean) => stale),
+      take(1)
+    );
   }
 
   /**
@@ -344,10 +366,10 @@ export class RequestService {
     // if it's not a GET request
     if (request.method !== RestRequestMethod.GET) {
       return true;
-    // if it is a GET request, check it isn't pending
+      // if it is a GET request, check it isn't pending
     } else if (this.isPending(request)) {
       return false;
-    // if it is pending, check if we're allowed to use a cached version
+      // if it is pending, check if we're allowed to use a cached version
     } else if (!useCachedVersionIfAvailable) {
       return true;
     } else {

src/app/core/data/root-data.service.spec.ts

@@ -1,16 +1,18 @@
 import { RootDataService } from './root-data.service';
 import { HALEndpointService } from '../shared/hal-endpoint.service';
-import { createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
-import { Observable, of } from 'rxjs';
+import {
+  createSuccessfulRemoteDataObject$,
+  createFailedRemoteDataObject$
+} from '../../shared/remote-data.utils';
+import { Observable } from 'rxjs';
 import { RemoteData } from './remote-data';
 import { Root } from './root.model';
-import { RawRestResponse } from '../dspace-rest/raw-rest-response.model';
 import { cold } from 'jasmine-marbles';
 
 describe('RootDataService', () => {
   let service: RootDataService;
   let halService: HALEndpointService;
-  let restService;
+  let requestService;
   let rootEndpoint;
   let findByHrefSpy;
 
@@ -19,10 +21,10 @@ describe('RootDataService', () => {
     halService = jasmine.createSpyObj('halService', {
       getRootHref: rootEndpoint,
     });
-    restService = jasmine.createSpyObj('halService', {
-      get: jasmine.createSpy('get'),
-    });
-    service = new RootDataService(null, null, null, halService, restService);
+    requestService = jasmine.createSpyObj('requestService', [
+      'setStaleByHref',
+    ]);
+    service = new RootDataService(requestService, null, null, halService);
 
     findByHrefSpy = spyOn(service as any, 'findByHref');
     findByHrefSpy.and.returnValue(createSuccessfulRemoteDataObject$({}));
@@ -47,12 +49,8 @@ describe('RootDataService', () => {
     let result$: Observable<boolean>;
 
     it('should return observable of true when root endpoint is available', () => {
-      const mockResponse = {
-        statusCode: 200,
-        statusText: 'OK'
-      } as RawRestResponse;
+      spyOn(service, 'findRoot').and.returnValue(createSuccessfulRemoteDataObject$<Root>({} as any));
 
-      restService.get.and.returnValue(of(mockResponse));
       result$ = service.checkServerAvailability();
 
       expect(result$).toBeObservable(cold('(a|)', {
@@ -61,12 +59,8 @@ describe('RootDataService', () => {
     });
 
     it('should return observable of false when root endpoint is not available', () => {
-      const mockResponse = {
-        statusCode: 500,
-        statusText: 'Internal Server Error'
-      } as RawRestResponse;
+      spyOn(service, 'findRoot').and.returnValue(createFailedRemoteDataObject$<Root>('500'));
 
-      restService.get.and.returnValue(of(mockResponse));
       result$ = service.checkServerAvailability();
 
       expect(result$).toBeObservable(cold('(a|)', {
@@ -75,4 +69,12 @@ describe('RootDataService', () => {
     });
 
   });
+
+  describe(`invalidateRootCache`, () => {
+    it(`should set the cached root request to stale`, () => {
+      service.invalidateRootCache();
+      expect(halService.getRootHref).toHaveBeenCalled();
+      expect(requestService.setStaleByHref).toHaveBeenCalledWith(rootEndpoint);
+    });
+  });
 });

src/app/core/data/root-data.service.ts

@@ -7,12 +7,11 @@ import { HALEndpointService } from '../shared/hal-endpoint.service';
 import { Observable, of as observableOf } from 'rxjs';
 import { RemoteData } from './remote-data';
 import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
-import { DspaceRestService } from '../dspace-rest/dspace-rest.service';
-import { RawRestResponse } from '../dspace-rest/raw-rest-response.model';
 import { catchError, map } from 'rxjs/operators';
 import { BaseDataService } from './base/base-data.service';
 import { ObjectCacheService } from '../cache/object-cache.service';
 import { dataService } from './base/data-service.decorator';
+import { getFirstCompletedRemoteData } from '../shared/operators';
 
 /**
  * A service to retrieve the {@link Root} object from the REST API.
@@ -25,21 +24,21 @@ export class RootDataService extends BaseDataService<Root> {
     protected rdbService: RemoteDataBuildService,
     protected objectCache: ObjectCacheService,
     protected halService: HALEndpointService,
-    protected restService: DspaceRestService,
   ) {
-    super('', requestService, rdbService, objectCache, halService, 6 * 60 * 60 * 1000);
+    super('', requestService, rdbService, objectCache, halService, 60 * 1000);
   }
 
   /**
    * Check if root endpoint is available
    */
   checkServerAvailability(): Observable<boolean> {
-    return this.restService.get(this.halService.getRootHref()).pipe(
+    return this.findRoot().pipe(
       catchError((err ) => {
         console.error(err);
         return observableOf(false);
       }),
-      map((res: RawRestResponse) => res.statusCode === 200)
+      getFirstCompletedRemoteData(),
+      map((rootRd: RemoteData<Root>) => rootRd.statusCode === 200)
     );
   }
 
@@ -60,6 +59,6 @@ export class RootDataService extends BaseDataService<Root> {
    * Set to sale the root endpoint cache hit
    */
   invalidateRootCache() {
-    this.requestService.setStaleByHrefSubstring(this.halService.getRootHref());
+    this.requestService.setStaleByHref(this.halService.getRootHref());
   }
 }

src/app/core/server-check/server-check.guard.spec.ts

@@ -1,68 +1,78 @@
 import { ServerCheckGuard } from './server-check.guard';
-import { Router } from '@angular/router';
+import { Router, NavigationStart, UrlTree, NavigationEnd, RouterEvent } from '@angular/router';
 
-import { of } from 'rxjs';
-import { take } from 'rxjs/operators';
-
-import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
+import { of, ReplaySubject } from 'rxjs';
 import { RootDataService } from '../data/root-data.service';
+import { TestScheduler } from 'rxjs/testing';
 import SpyObj = jasmine.SpyObj;
 
 describe('ServerCheckGuard', () => {
   let guard: ServerCheckGuard;
-  let router: SpyObj<Router>;
+  let router: Router;
+  const eventSubject = new ReplaySubject<RouterEvent>(1);
   let rootDataServiceStub: SpyObj<RootDataService>;
-
-  rootDataServiceStub = jasmine.createSpyObj('RootDataService', {
-    checkServerAvailability: jasmine.createSpy('checkServerAvailability'),
-    invalidateRootCache: jasmine.createSpy('invalidateRootCache')
-  });
-  router = jasmine.createSpyObj('Router', {
-    navigateByUrl: jasmine.createSpy('navigateByUrl')
-  });
+  let testScheduler: TestScheduler;
+  let redirectUrlTree: UrlTree;
 
   beforeEach(() => {
+    testScheduler = new TestScheduler((actual, expected) => {
+      expect(actual).toEqual(expected);
+    });
+    rootDataServiceStub = jasmine.createSpyObj('RootDataService', {
+      checkServerAvailability: jasmine.createSpy('checkServerAvailability'),
+      invalidateRootCache: jasmine.createSpy('invalidateRootCache')
+    });
+    redirectUrlTree = new UrlTree();
+    router = {
+      events: eventSubject.asObservable(),
+      navigateByUrl: jasmine.createSpy('navigateByUrl'),
+      parseUrl: jasmine.createSpy('parseUrl').and.returnValue(redirectUrlTree)
+    } as any;
     guard = new ServerCheckGuard(router, rootDataServiceStub);
   });
 
-  afterEach(() => {
-    router.navigateByUrl.calls.reset();
-    rootDataServiceStub.invalidateRootCache.calls.reset();
-  });
-
   it('should be created', () => {
     expect(guard).toBeTruthy();
   });
 
-  describe('when root endpoint has succeeded', () => {
+  describe('when root endpoint request has succeeded', () => {
     beforeEach(() => {
       rootDataServiceStub.checkServerAvailability.and.returnValue(of(true));
     });
 
-    it('should not redirect to error page', () => {
-      guard.canActivateChild({} as any, {} as any).pipe(
-        take(1)
-      ).subscribe((canActivate: boolean) => {
-        expect(canActivate).toEqual(true);
-        expect(rootDataServiceStub.invalidateRootCache).not.toHaveBeenCalled();
-        expect(router.navigateByUrl).not.toHaveBeenCalled();
+    it('should return true', () => {
+      testScheduler.run(({ expectObservable }) => {
+        const result$ = guard.canActivateChild({} as any, {} as any);
+        expectObservable(result$).toBe('(a|)', { a: true });
       });
     });
   });
 
-  describe('when root endpoint has not succeeded', () => {
+  describe('when root endpoint request has not succeeded', () => {
     beforeEach(() => {
       rootDataServiceStub.checkServerAvailability.and.returnValue(of(false));
     });
 
-    it('should redirect to error page', () => {
-      guard.canActivateChild({} as any, {} as any).pipe(
-        take(1)
-      ).subscribe((canActivate: boolean) => {
-        expect(canActivate).toEqual(false);
-        expect(rootDataServiceStub.invalidateRootCache).toHaveBeenCalled();
-        expect(router.navigateByUrl).toHaveBeenCalledWith(getPageInternalServerErrorRoute());
+    it('should return a UrlTree with the route to the 500 error page', () => {
+      testScheduler.run(({ expectObservable }) => {
+        const result$ = guard.canActivateChild({} as any, {} as any);
+        expectObservable(result$).toBe('(b|)', { b: redirectUrlTree });
       });
+      expect(router.parseUrl).toHaveBeenCalledWith('/500');
+    });
+  });
+
+  describe(`listenForRouteChanges`, () => {
+    it(`should invalidate the root cache on every NavigationStart event`, () => {
+        testScheduler.run(() => {
+          guard.listenForRouteChanges();
+          eventSubject.next(new NavigationStart(1,''));
+          eventSubject.next(new NavigationEnd(1,'', ''));
+          eventSubject.next(new NavigationStart(2,''));
+          eventSubject.next(new NavigationEnd(2,'', ''));
+          eventSubject.next(new NavigationStart(3,''));
+        });
+        expect(rootDataServiceStub.invalidateRootCache).toHaveBeenCalledTimes(3);
     });
   });
 });

src/app/core/server-check/server-check.guard.ts

@@ -1,8 +1,15 @@
 import { Injectable } from '@angular/core';
-import { ActivatedRouteSnapshot, CanActivateChild, Router, RouterStateSnapshot } from '@angular/router';
+import {
+  ActivatedRouteSnapshot,
+  CanActivateChild,
+  Router,
+  RouterStateSnapshot,
+  UrlTree,
+  NavigationStart
+} from '@angular/router';
 
 import { Observable } from 'rxjs';
-import { take, tap } from 'rxjs/operators';
+import { take, map, filter } from 'rxjs/operators';
 
 import { RootDataService } from '../data/root-data.service';
 import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
@@ -23,17 +30,32 @@ export class ServerCheckGuard implements CanActivateChild {
    */
   canActivateChild(
     route: ActivatedRouteSnapshot,
-    state: RouterStateSnapshot): Observable<boolean> {
+    state: RouterStateSnapshot
+  ): Observable<boolean | UrlTree> {
 
     return this.rootDataService.checkServerAvailability().pipe(
       take(1),
-      tap((isAvailable: boolean) => {
+      map((isAvailable: boolean) => {
         if (!isAvailable) {
-          this.rootDataService.invalidateRootCache();
-          this.router.navigateByUrl(getPageInternalServerErrorRoute());
+          return this.router.parseUrl(getPageInternalServerErrorRoute());
+        } else {
+          return true;
         }
       })
     );
+  }
 
+  /**
+   * Listen to all router events. Every time a new navigation starts, invalidate the cache
+   * for the root endpoint. That way we retrieve it once per routing operation to ensure the
+   * backend is not down. But if the guard is called multiple times during the same routing
+   * operation, the cached version is used.
+   */
+  listenForRouteChanges(): void {
+    this.router.events.pipe(
+      filter(event => event instanceof NavigationStart),
+    ).subscribe(() => {
+      this.rootDataService.invalidateRootCache();
+    });
   }
 }

src/modules/app/browser-init.service.ts

@@ -32,6 +32,7 @@ import { logStartupMessage } from '../../../startup-message';
 import { MenuService } from '../../app/shared/menu/menu.service';
 import { RootDataService } from '../../app/core/data/root-data.service';
 import { firstValueFrom, Subscription } from 'rxjs';
+import { ServerCheckGuard } from '../../app/core/server-check/server-check.guard';
 
 /**
  * Performs client-side initialization.
@@ -56,7 +57,8 @@ export class BrowserInitService extends InitService {
     protected authService: AuthService,
     protected themeService: ThemeService,
     protected menuService: MenuService,
-    private rootDataService: RootDataService
+    private rootDataService: RootDataService,
+    protected serverCheckGuard: ServerCheckGuard,
   ) {
     super(
       store,
@@ -172,4 +174,13 @@ export class BrowserInitService extends InitService {
       });
   }
 
+  /**
+   * Start route-listening subscriptions
+   * @protected
+   */
+  protected initRouteListeners(): void {
+    super.initRouteListeners();
+    this.serverCheckGuard.listenForRouteChanges();
+  }
+
 }