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    <p>You can use the task queue and the datastore. You need 3 handlers:</p> <ol> <li>The task handler, doing the hard work. It will store its progress in the datastore.</li> <li>A handler that starts the task in the background and returns the 'blank' page</li> <li>A handler to get the status</li> </ol> <p>Note: The page cannot be really blank. It must have javascript on it that checks the status. I think this is true with the <code>Channel API</code> too.</p> <p>Anyway heres the code in Python:</p> <pre><code>class LongTaskStatus(ndb.Model): is_complete = ndb.BooleanProperty() percentage = ndb.FloatProperty() messages = ndb.StringProperty(repeated=True) class LongTaskHandler(webapp2.RequestHandler): def get(self): # Query for existing status model or create a new one # Does work ... # Update progress status = LongTaskStatus() status.messages.appen('Still busy...') status.put() # Does work ... class StartHandler(webapp2.RequestHandler): def get(self): # start the task taskqueue.add(url='/longtask') # Return a page which uses javascript to check the progress every few seconds template = JINJA_ENVIRONMENT.get_template('taskprogress.html') self.response.write(template.render(template_values)) class CheckTaskStatus(wenapp2.RequestHandler): def get(self): query = LongTaskStatus.query().fetch(1) result = {} if query: status = query[0] result = { 'is_complete': status.is_complete, 'percentage': status.percentage, 'messages': status.messages } self.response.write(json.dumps(result)) </code></pre> <p>and heres the "blank" page:</p> <pre><code>&lt;!DOCTYPE html&gt; &lt;html lang="en"&gt; &lt;body&gt; &lt;div id="status"&gt;&lt;/div&gt; &lt;script&gt; window.setInterval(function(){ $.get( "ajax/test.html", function( data ) { $( ".status" ).html( data ); }); }, 5000); &lt;/script&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p><strong>Edit: Other option without Task Queue</strong></p> <p>If you have a unique way of identifying the task <strong>before it is started</strong> you could potentially speed this method up by not using the task queue api.</p> <p>Heres how:</p> <ol> <li>Call the LongTaskHandler via javascript</li> <li>Redirect to a loading page, which calls CheckTaskStatus.</li> </ol> <p>This should be faster than using task queues, but unfortunately you need a way to identify the task before it is started. eg userid, session etc</p>
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    1. COThanks for the answer! It seems that such an approach would work. But I'm a bit afraid of the delay between the moment a task is added to the queue and when it is processed... Isn't this quite significant (tens of seconds at least)? Because, if that's the case, a considerable delay would appear for the users (considering that the processing should only take 30-40 seconds) and they would have to wait looking at a screen with a 'loading' indicator.
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    2. COUnfortunately the only way to return immediately is to start a background task.
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    3. COI just thought of a way to avoid the task queue, I edited my post with it. Also, have a look here for some information about controlling task queues: https://developers.google.com/appengine/docs/python/config/queue
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