[CST-4880] Add ServerCheckGuard in order to show internal server error page when rest server is not available

Author: atarix83

src/app/app-routing-paths.ts

@@ -89,6 +89,12 @@ export function getPageNotFoundRoute() {
   return `/${PAGE_NOT_FOUND_PATH}`;
 }
 
+export const INTERNAL_SERVER_ERROR = '500';
+
+export function getPageInternalServerErrorRoute() {
+  return `/${INTERNAL_SERVER_ERROR}`;
+}
+
 export const INFO_MODULE_PATH = 'info';
 export function getInfoModulePath() {
   return `/${INFO_MODULE_PATH}`;

src/app/app-routing.module.ts

@@ -11,10 +11,12 @@ import {
   FORBIDDEN_PATH,
   FORGOT_PASSWORD_PATH,
   INFO_MODULE_PATH,
+  INTERNAL_SERVER_ERROR,
+  LEGACY_BITSTREAM_MODULE_PATH,
   PROFILE_MODULE_PATH,
   REGISTER_PATH,
+  REQUEST_COPY_MODULE_PATH,
   WORKFLOW_ITEM_MODULE_PATH,
-  LEGACY_BITSTREAM_MODULE_PATH, REQUEST_COPY_MODULE_PATH,
 } from './app-routing-paths';
 import { COLLECTION_MODULE_PATH } from './collection-page/collection-page-routing-paths';
 import { COMMUNITY_MODULE_PATH } from './community-page/community-page-routing-paths';
@@ -26,14 +28,25 @@ import { SiteRegisterGuard } from './core/data/feature-authorization/feature-aut
 import { ThemedPageNotFoundComponent } from './pagenotfound/themed-pagenotfound.component';
 import { ThemedForbiddenComponent } from './forbidden/themed-forbidden.component';
 import { GroupAdministratorGuard } from './core/data/feature-authorization/feature-authorization-guard/group-administrator.guard';
+import { ThemedPageInternalServerErrorComponent } from './page-internal-server-error/themed-page-internal-server-error.component';
+import { ServerCheckGuard } from './core/server-check/server-check.guard';
 
 @NgModule({
   imports: [
-    RouterModule.forRoot([{
-      path: '', canActivate: [AuthBlockingGuard],
+    RouterModule.forRoot([
+      { path: INTERNAL_SERVER_ERROR, component: ThemedPageInternalServerErrorComponent },
+      {
+        path: '',
+        canActivate: [AuthBlockingGuard],
+        canActivateChild: [ServerCheckGuard],
         children: [
           { path: '', redirectTo: '/home', pathMatch: 'full' },
-          { path: 'reload/:rnd', component: ThemedPageNotFoundComponent, pathMatch: 'full', canActivate: [ReloadGuard] },
+          {
+            path: 'reload/:rnd',
+            component: ThemedPageNotFoundComponent,
+            pathMatch: 'full',
+            canActivate: [ReloadGuard]
+          },
           {
             path: 'home',
             loadChildren: () => import('./home-page/home-page.module')
@@ -89,7 +102,8 @@ import { GroupAdministratorGuard } from './core/data/feature-authorization/featu
               .then((m) => m.ItemPageModule),
             canActivate: [EndUserAgreementCurrentUserGuard]
           },
-          { path: 'entities/:entity-type',
+          {
+            path: 'entities/:entity-type',
             loadChildren: () => import('./item-page/item-page.module')
               .then((m) => m.ItemPageModule),
             canActivate: [EndUserAgreementCurrentUserGuard]
@@ -133,12 +147,12 @@ import { GroupAdministratorGuard } from './core/data/feature-authorization/featu
           {
             path: 'login',
             loadChildren: () => import('./login-page/login-page.module')
-              .then((m) => m.LoginPageModule),
+              .then((m) => m.LoginPageModule)
           },
           {
             path: 'logout',
             loadChildren: () => import('./logout-page/logout-page.module')
-              .then((m) => m.LogoutPageModule),
+              .then((m) => m.LogoutPageModule)
           },
           {
             path: 'submit',
@@ -178,7 +192,7 @@ import { GroupAdministratorGuard } from './core/data/feature-authorization/featu
           },
           {
             path: INFO_MODULE_PATH,
-            loadChildren: () => import('./info/info.module').then((m) => m.InfoModule),
+            loadChildren: () => import('./info/info.module').then((m) => m.InfoModule)
           },
           {
             path: REQUEST_COPY_MODULE_PATH,
@@ -192,17 +206,18 @@ import { GroupAdministratorGuard } from './core/data/feature-authorization/featu
           {
             path: 'statistics',
             loadChildren: () => import('./statistics-page/statistics-page-routing.module')
-              .then((m) => m.StatisticsPageRoutingModule),
+              .then((m) => m.StatisticsPageRoutingModule)
           },
           {
             path: ACCESS_CONTROL_MODULE_PATH,
             loadChildren: () => import('./access-control/access-control.module').then((m) => m.AccessControlModule),
             canActivate: [GroupAdministratorGuard],
           },
           { path: '**', pathMatch: 'full', component: ThemedPageNotFoundComponent },
-      ]}
-    ],{
-    onSameUrlNavigation: 'reload',
+        ]
+      }
+    ], {
+      onSameUrlNavigation: 'reload',
 })
   ],
   exports: [RouterModule],

src/app/app.module.ts

@@ -54,8 +54,10 @@ import { ThemedFooterComponent } from './footer/themed-footer.component';
 import { ThemedBreadcrumbsComponent } from './breadcrumbs/themed-breadcrumbs.component';
 import { ThemedHeaderNavbarWrapperComponent } from './header-nav-wrapper/themed-header-navbar-wrapper.component';
 import { IdleModalComponent } from './shared/idle-modal/idle-modal.component';
+import { ThemedPageInternalServerErrorComponent } from './page-internal-server-error/themed-page-internal-server-error.component';
+import { PageInternalServerErrorComponent } from './page-internal-server-error/page-internal-server-error.component';
 
-import { AppConfig, APP_CONFIG } from '../config/app-config.interface';
+import { APP_CONFIG, AppConfig } from '../config/app-config.interface';
 
 export function getConfig() {
   return environment;
@@ -181,7 +183,9 @@ const DECLARATIONS = [
   ThemedBreadcrumbsComponent,
   ForbiddenComponent,
   ThemedForbiddenComponent,
-  IdleModalComponent
+  IdleModalComponent,
+  ThemedPageInternalServerErrorComponent,
+  PageInternalServerErrorComponent
 ];
 
 const EXPORTS = [

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

@@ -1,21 +1,27 @@
 import { RootDataService } from './root-data.service';
 import { HALEndpointService } from '../shared/hal-endpoint.service';
 import { createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
-import { Observable } from 'rxjs';
+import { Observable, of } 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 rootEndpoint;
 
   beforeEach(() => {
     rootEndpoint = 'root-endpoint';
     halService = jasmine.createSpyObj('halService', {
       getRootHref: rootEndpoint
     });
-    service = new RootDataService(null, null, null, null, halService, null, null, null);
+    restService = jasmine.createSpyObj('halService', {
+      get: jasmine.createSpy('get')
+    });
+    service = new RootDataService(null, null, null, null, halService, null, null, null, restService);
     (service as any).dataService = jasmine.createSpyObj('dataService', {
       findByHref: createSuccessfulRemoteDataObject$({})
     });
@@ -35,4 +41,37 @@ describe('RootDataService', () => {
       });
     });
   });
+
+  describe('checkServerAvailability', () => {
+    let result$: Observable<boolean>;
+
+    it('should return observable of true when root endpoint is available', () => {
+      const mockResponse = {
+        statusCode: 200,
+        statusText: 'OK'
+      } as RawRestResponse;
+
+      restService.get.and.returnValue(of(mockResponse));
+      result$ = service.checkServerAvailability();
+
+      expect(result$).toBeObservable(cold('(a|)', {
+        a: true
+      }));
+    });
+
+    it('should return observable of false when root endpoint is not available', () => {
+      const mockResponse = {
+        statusCode: 500,
+        statusText: 'Internal Server Error'
+      } as RawRestResponse;
+
+      restService.get.and.returnValue(of(mockResponse));
+      result$ = service.checkServerAvailability();
+
+      expect(result$).toBeObservable(cold('(a|)', {
+        a: false
+      }));
+    });
+
+  });
 });

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

@@ -17,6 +17,10 @@ import { RemoteData } from './remote-data';
 import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
 import { FindListOptions } from './request.models';
 import { PaginatedList } from './paginated-list.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 { of } from 'rxjs/internal/observable/of';
 
 /* tslint:disable:max-classes-per-file */
 
@@ -59,10 +63,24 @@ export class RootDataService {
     protected halService: HALEndpointService,
     protected notificationsService: NotificationsService,
     protected http: HttpClient,
-    protected comparator: DefaultChangeAnalyzer<Root>) {
+    protected comparator: DefaultChangeAnalyzer<Root>,
+    protected restService: DspaceRestService) {
     this.dataService = new DataServiceImpl(requestService, rdbService, null, objectCache, halService, notificationsService, http, comparator);
   }
 
+  /**
+   * Check if root endpoint is available
+   */
+  checkServerAvailability(): Observable<boolean> {
+    return this.restService.get(this.halService.getRootHref()).pipe(
+      catchError((err ) => {
+        console.error(err);
+        return of(false);
+      }),
+      map((res: RawRestResponse) => res.statusCode === 200)
+    );
+  }
+
   /**
    * Find the {@link Root} object of the REST API
    * @param useCachedVersionIfAvailable If this is true, the request will only be sent if there's
@@ -106,5 +124,12 @@ export class RootDataService {
   findAllByHref(href: string | Observable<string>, findListOptions: FindListOptions = {}, useCachedVersionIfAvailable = true, reRequestOnStale = true, ...linksToFollow: FollowLinkConfig<Root>[]): Observable<RemoteData<PaginatedList<Root>>> {
     return this.dataService.findAllByHref(href, findListOptions, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow);
   }
+
+  /**
+   * Set to sale the root endpoint cache hit
+   */
+  invalidateRootCache() {
+    this.requestService.setStaleByHrefSubstring('server/api');
+  }
 }
 /* tslint:enable:max-classes-per-file */

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

@@ -0,0 +1,68 @@
+import { ServerCheckGuard } from './server-check.guard';
+import { Router } from '@angular/router';
+
+import { of } from 'rxjs';
+import { take } from 'rxjs/operators';
+
+import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
+import { RootDataService } from '../data/root-data.service';
+import SpyObj = jasmine.SpyObj;
+
+describe('ServerCheckGuard', () => {
+  let guard: ServerCheckGuard;
+  let router: SpyObj<Router>;
+  let rootDataServiceStub: SpyObj<RootDataService>;
+
+  rootDataServiceStub = jasmine.createSpyObj('RootDataService', {
+    checkServerAvailability: jasmine.createSpy('checkServerAvailability'),
+    invalidateRootCache: jasmine.createSpy('invalidateRootCache')
+  });
+  router = jasmine.createSpyObj('Router', {
+    navigateByUrl: jasmine.createSpy('navigateByUrl')
+  });
+
+  beforeEach(() => {
+    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', () => {
+    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();
+      });
+    });
+  });
+
+  describe('when root endpoint 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());
+      });
+    });
+  });
+});

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

@@ -0,0 +1,39 @@
+import { Injectable } from '@angular/core';
+import { ActivatedRouteSnapshot, CanActivateChild, Router, RouterStateSnapshot } from '@angular/router';
+
+import { Observable } from 'rxjs';
+import { take, tap } from 'rxjs/operators';
+
+import { RootDataService } from '../data/root-data.service';
+import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
+
+@Injectable({
+  providedIn: 'root'
+})
+/**
+ * A guard that checks if root api endpoint is reachable.
+ * If not redirect to 500 error page
+ */
+export class ServerCheckGuard implements CanActivateChild {
+  constructor(private router: Router, private rootDataService: RootDataService) {
+  }
+
+  /**
+   * True when root api endpoint is reachable.
+   */
+  canActivateChild(
+    route: ActivatedRouteSnapshot,
+    state: RouterStateSnapshot): Observable<boolean> {
+
+    return this.rootDataService.checkServerAvailability().pipe(
+      take(1),
+      tap((isAvailable: boolean) => {
+        if (!isAvailable) {
+          this.rootDataService.invalidateRootCache();
+          this.router.navigateByUrl(getPageInternalServerErrorRoute());
+        }
+      })
+    );
+
+  }
+}

src/app/core/services/server-response.service.ts

@@ -31,4 +31,8 @@ export class ServerResponseService {
   setNotFound(message = 'Not found'): this {
     return this.setStatus(404, message);
   }
+
+  setInternalServerError(message = 'Internal Server Error'): this {
+    return this.setStatus(500, message);
+  }
 }

src/app/page-internal-server-error/page-internal-server-error.component.html

@@ -0,0 +1,10 @@
+<div class="page-internal-server-error container">
+  <h1>500</h1>
+  <h2><small>{{"500.page-internal-server-error" | translate}}</small></h2>
+  <br/>
+  <p>{{"500.help" | translate}}</p>
+  <br/>
+  <p class="text-center">
+    <a href="/home" class="btn btn-primary">{{"500.link.home-page" | translate}}</a>
+  </p>
+</div>