ngw qgis rendering error

error.log

Traceback (most recent call last):
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/router.py", line 270, in __call__
    response = self.execution_policy(environ, self)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/router.py", line 279, in default_execution_policy
    return request.invoke_exception_view(reraise=True)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/view.py", line 768, in invoke_exception_view
    reraise_(*exc_info)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/router.py", line 277, in default_execution_policy
    return router.invoke_request(request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/router.py", line 249, in invoke_request
    response = handle_request(request)
  File "/opt/ngw/package/nextgisweb/nextgisweb/pyramid/api.py", line 89, in cors_tween
    response = handler(request)
  File "/opt/ngw/package/nextgisweb/nextgisweb/resource/api.py", line 99, in resource_exception_tween
    response = handler(request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid_tm/__init__.py", line 171, in tm_tween
    reraise(*exc_info)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid_tm/__init__.py", line 136, in tm_tween
    response = handler(request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/tweens.py", line 43, in excview_tween
    response = _error_handler(request, exc)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/tweens.py", line 17, in _error_handler
    reraise(*exc_info)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/tweens.py", line 41, in excview_tween
    response = handler(request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/router.py", line 148, in handle_request
    registry, request, context, context_iface, view_name
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/view.py", line 657, in _call_view
    response = view_callable(context, request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/viewderivers.py", line 275, in wrapper
    response = view(context, request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/viewderivers.py", line 401, in viewresult_to_response
    result = view(context, request)
  File "/opt/ngw/env/local/lib/python2.7/site-packages/pyramid/viewderivers.py", line 144, in _requestonly_view
    response = view(request)
  File "/opt/ngw/package/nextgisweb/nextgisweb/render/api.py", line 74, in image
    rimg = req.render_extent(p_extent, p_size)
  File "/opt/ngw/package/nextgisweb_qgis/nextgisweb_qgis/model.py", line 156, in render_extent
    return self.style._render_image(self.srs, extent, size, self.cond)
  File "/opt/ngw/package/nextgisweb_qgis/nextgisweb_qgis/model.py", line 126, in _render_image
    res_img = result.get(block=True, timeout=render_timeout)
  File "/usr/lib/python2.7/Queue.py", line 176, in get
    raise Empty
Queue.Empty
[pid: 40|app: 0|req: 30/542] 176.99.243.55 () {40 vars in 1103 bytes} [Tue Apr 23 23:44:51 2019] GET /api/component/render/image?resource=57&extent=3356683.12967227,8360101.710149039,3359062.2321776464,8361886.037028071&size=996,747 => generated 0 bytes in 10027 msecs (HTTP/1.1 500) 0 headers in 0 bytes (0 switches on core 0)