How to transfer (output) text data to jinja2 template for flash application in pythonanywhere

Question

I am trying to implement "streaming content" in my Pythonanywhere account.

This is more or less similar to what is shown there: cf http://flask.pocoo.org/docs/0.10/patterns/streaming/

except that my view calculates a complex process, perhaps one minute, and gives its data to my template, where it is assumed that the script is updating some progress indicators (`` source.onmessage '').

This works fine on my development machine, but not on my pythonanywhere account. On this server, the process looks jammed (progress indicators are never updated, except at the very end, where suddunly grows from 0% to 100%), although everything goes well under the hood, for example. my statements are printcorrectly displayed in my server logs).

There is a note in the above snippet:

Note that some WSGI intermediaries can break threads, so you can turn it on carefully in the debugging environment with profilers and other things.

Maybe the problem is here? and will it be a detour?

JS code from my jinja2 template:

    <script type="text/javascript">
    /* progress bar */
    var source = new EventSource("{{ url_for('BP.run', mylongprocess_id=mylongprocess_id) }}");
    source.onmessage = function(event) {
        console.log(event.data);
        var data = event.data.split("!!");
        var nodeid = data[0];
        var process = data[1];
        var process_status = data[2];
        var postpro = data[3];
        var postpro_status = data[4];
        $('.pb1').css('width', process+'%').attr('aria-valuenow', process);   
        $('.pb2').css('width', postpro+'%').attr('aria-valuenow', process);   
        document.getElementById("process_status").innerHTML = process_status;
        document.getElementById("postpro_status").innerHTML = postpro_status;
        document.getElementById("nodeid").innerHTML = nodeid;
        if (postpro >= 100) {
            setTimeout(function() {
                console.log("progress is finished!");
                document.getElementById("status").innerHTML = "redirecting to {{url_for('.view_sonix_result', mylongprocess_id=mylongprocess_id)}}";
                window.location.replace("{{url_for('.terminate_analysis', mylongprocess_id=mylongprocess_id)}}");
                                  }, 2); // / setTimeout function
            } // /if
        else {
            document.getElementById("status").innerHTML = "pending...";
            } // /else
        } // /function
</script>

My (simplified) view:

@BP.route('/run/<int:mylongprocess_id>')
@login_required
def run(mylongprocess_id):
    mylongprocess = mylongprocess.query.get_or_404(mylongprocess_id)
    project = Project.query.get_or_404(mylongprocess.project_id)
    check_rights(current_user, project, 'user', 404)
    A, lcs = _create_analysis(mylongprocess)
    @copy_current_request_context
    def gen(mylongprocess, nodeid, store_path):
        print('now runing %s' % A)
        for (loopnb, total_loops, pct, lclabel) in A.runiterator(lcs):
            print('ran %d/%d (%.1f%%) "%s"' % (loopnb, total_loops,
                                               pct, lclabel))
            progress = ('data: %s!!%f!!%s!!%f!!%s\n\n' %
                        (nodeid, pct, lclabel, 0, 'waiting...'))
            yield progress
        print('now postprocessing %s' % A)
        postpro = load_node(store_path, node_id=nodeid)
        for step, total, pct, action in postpro._builditer(target='web',
                                                       buildfile=None):
            progress = ('data: %s!!%f!!%s!!%f!!%s\n\n' %
                        (nodeid, 100, 'ok',  pct, action.replace('_', ' ')))
            yield progress
        print('now terminating %s' % A)
        _terminate_analysis(A, mylongprocess)

    return Response(gen(mylongprocess, mylongprocess.nodeid), mimetype='text/event-stream')

Answer 1

- nginx, PythonAnywhere, nginx , .

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• response.headers['X-Accel-Buffering'] = 'no'
• '\n' , , python .