title: Angular2 RxJS - split collection of urls to fetch into smaller chunks
body: <p>I use Angular2.4.8. I have collection of url to fetch (dozens of them). Currently I fetch them all at once but it often happens that server can't handle so many requests simultaneously. Current code:</p>
  
  <pre><code>let collectionsRequests = Array.from(collectionsUrls, url =&gt; this.http.get(url));
  Observable.forkJoin(collectionsRequests).subscribe((collectionResponses: Response[]) =&gt; {
      collectionResponses.forEach(response =&gt; {
          // parse responses
      });
  });
  </code></pre>
  
  <p>where <code>collectionsUrls</code> is array of strings (urls) to fetch.</p>
  
  <p>I'd like to divide those requests to packs with 10 requests and when one pack is finished then next pack start until end of array.</p>
  
  <p>I tried to use <code>bufferCount</code> and <code>concatMap</code> but with no success. Although probably this is a good direction. How should it look like?</p>