Hello,
I have this warning using the 8.1.0-beta2 version :
Warning: Memcached::setMulti(): failed to set key cache_discovery7-views_data%3Aen in Drupal\memcache_storage\DrupalMemcached->setMulti() (line 136 of modules/contrib/memcache_storage/src/DrupalMemcached.php).
Drupal\memcache_storage\DrupalMemcached->setMulti(Array, 'cache_discovery') (Line: 162)
Drupal\memcache_storage\MemcachedBackend->setMultiple(Array) (Line: 120)
Drupal\memcache_storage\MemcachedBackend->set('views_data:en', Array, -1, Array) (Line: 198)
Drupal\views\ViewsData->cacheSet('views_data', Array) (Line: 246)
Drupal\views\ViewsData->getData() (Line: 135)
Drupal\views\ViewsData->get('node_field_data') (Line: 1163)
Drupal\views\ViewExecutable->initQuery() (Line: 1209)
Drupal\views\ViewExecutable->build(NULL) (Line: 1377)
Drupal\views\ViewExecutable->execute(NULL) (Line: 1440)
Drupal\views\ViewExecutable->render() (Line: 35)
Drupal\blab_twig_extensions\DisplayViewExtension->display_view('2_random_activity_or_sub_activity') (Line: 88)
__TwigTemplate_db74de76c4b8643deae542326d8d535b2aa213571d298c6bc12cf291efba98ca->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array) (Line: 366)
Twig_Template->render(Array) (Line: 64)
twig_render_template('themes/custom/nctps/templates/block/block--header.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('block', Array) (Line: 435)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 448)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 468)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 70)
__TwigTemplate_5a9ec93f050dffe81ad8a7a7620e3bab9059ea7aaa05bd16913317f7ecca3b6c->block_navbar(Array, Array) (Line: 167)
Twig_Template->displayBlock('navbar', Array, Array, ) (Line: 185)
Twig_Template->displayBlock('navbar', Array, Array, ) (Line: 126)
Twig_Template->displayParentBlock('navbar', Array, Array) (Line: 56)
__TwigTemplate_0e1ad8e644113c0c5748ce81a67153c5ce228dcb7895fc53ace1e4036379fa85->block_navbar(Array, Array) (Line: 167)
Twig_Template->displayBlock('navbar', Array, Array) (Line: 59)
__TwigTemplate_45146e7256fd67b684e90900ad37f182066a633835792b817d1c53d8978bbf4e->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array, Array) (Line: 62)
__TwigTemplate_5a9ec93f050dffe81ad8a7a7620e3bab9059ea7aaa05bd16913317f7ecca3b6c->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array, Array) (Line: 48)
__TwigTemplate_90bf19b60edee8729012d84091c972dfab29ef862c0e26ae7bb2aefbfd8921dc->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array, Array) (Line: 49)
__TwigTemplate_0e1ad8e644113c0c5748ce81a67153c5ce228dcb7895fc53ace1e4036379fa85->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array) (Line: 366)
Twig_Template->render(Array) (Line: 64)
twig_render_template('themes/custom/nctps/templates/page--node--type-experiences.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('page', Array) (Line: 435)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 468)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 95)
__TwigTemplate_9b3ca8251e07f7e15f38caada4889f29d69e1945686356ccaf22874fc4b0240e->doDisplay(Array, Array) (Line: 387)
Twig_Template->displayWithErrorHandling(Array, Array) (Line: 355)
Twig_Template->display(Array) (Line: 366)
Twig_Template->render(Array) (Line: 64)
twig_render_template('themes/custom/nctps/templates/html.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('html', Array) (Line: 435)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 147)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 148)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object) (Line: 149)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 98)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 77)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 630)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)
Look like it's related to the php memcache extension.
I'm using php7.0.8 with https://github.com/php-memcached-dev/php-memcached php7 branch