reduce number of unnecessary requests from HalEndpointService and RemoteDataBuildService

src/app/core/cache/builders/remote-data-build.service.ts

@@ -161,7 +161,10 @@ export class RemoteDataBuildService {
         const objectList = normalized[relationship].page || normalized[relationship];
         if (typeof objectList !== 'string') {
           objectList.forEach((href: string) => {
-            this.requestService.configure(new GetRequest(this.requestService.generateRequestId(), href))
+            const request = new GetRequest(this.requestService.generateRequestId(), href);
+            if (!this.requestService.isCachedOrPending(request)) {
+              this.requestService.configure(request)
+            }
           });
 
           const rdArr = [];
@@ -175,7 +178,10 @@ export class RemoteDataBuildService {
             result = rdArr[0];
           }
         } else {
-          this.requestService.configure(new GetRequest(this.requestService.generateRequestId(), objectList));
+          const request = new GetRequest(this.requestService.generateRequestId(), objectList);
+          if (!this.requestService.isCachedOrPending(request)) {
+            this.requestService.configure(request)
+          }
 
           // The rest API can return a single URL to represent a list of resources (e.g. /items/:id/bitstreams)
           // in that case only 1 href will be stored in the normalized obj (so the isArray above fails),

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

@@ -151,6 +151,8 @@ export class FindAllRequest extends GetRequest {
 }
 
 export class EndpointMapRequest extends GetRequest {
+  public responseMsToLive = Number.MAX_SAFE_INTEGER;
+
   constructor(
     uuid: string,
     href: string,

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

@@ -222,7 +222,7 @@ export class RequestService {
    * @param {GetRequest} request The request to check
    * @returns {boolean} True if the request is cached or still pending
    */
-  private isCachedOrPending(request: GetRequest): boolean {
+  public isCachedOrPending(request: GetRequest): boolean {
     const inReqCache = this.hasByHref(request.href);
     const inObjCache = this.objectCache.hasBySelfLink(request.href);
     const isCached = inReqCache || inObjCache;

src/app/core/shared/hal-endpoint.service.ts

@@ -4,13 +4,14 @@ import {
   map,
   mergeMap,
   startWith,
-  switchMap,
+  switchMap, take,
   tap
 } from 'rxjs/operators';
+import { RequestEntry } from '../data/request.reducer';
 import { RequestService } from '../data/request.service';
 import { GlobalConfig } from '../../../config/global-config.interface';
 import { EndpointMapRequest } from '../data/request.models';
-import { hasValue, isEmpty, isNotEmpty } from '../../shared/empty.util';
+import { hasNoValue, hasValue, isEmpty, isNotEmpty } from '../../shared/empty.util';
 import { RESTURLCombiner } from '../url-combiner/rest-url-combiner';
 import { Inject, Injectable } from '@angular/core';
 import { GLOBAL_CONFIG } from '../../../config';
@@ -36,15 +37,19 @@ export class HALEndpointService {
   private getEndpointMapAt(href): Observable<EndpointMap> {
     const request = new EndpointMapRequest(this.requestService.generateRequestId(), href);
 
+    if (!this.requestService.isCachedOrPending(request)) {
+      // don't bother configuring the request if it's already cached or pending.
       this.requestService.configure(request);
+    }
+
     return this.requestService.getByHref(request.href).pipe(
       getResponseFromEntry(),
       map((response: EndpointMapSuccessResponse) => response.endpointMap),
       );
   }
 
-  public getEndpoint(linkPath: string): Observable<string> {
+  public getEndpoint(linkPath: string, startHref?: string): Observable<string> {
-    return this.getEndpointAt(this.getRootHref(), ...linkPath.split('/'));
+    return this.getEndpointAt(startHref || this.getRootHref(), ...linkPath.split('/')).pipe(take(1));
   }
 
   /**
@@ -71,10 +76,11 @@ export class HALEndpointService {
     ) as Observable<string>;
 
     if (halNames.length === 1) {
-      return nextHref$;
+      return nextHref$.pipe(take(1));
     } else {
       return nextHref$.pipe(
-        switchMap((nextHref) => this.getEndpointAt(nextHref, ...halNames.slice(1)))
+        switchMap((nextHref) => this.getEndpointAt(nextHref, ...halNames.slice(1))),
+        take(1)
       );
     }
   }