Have intermediary reload only after preliminary caching

src/octoprint/server/util/flask.py

@@ -312,6 +312,18 @@ class LessSimpleCache(BaseCache):
 			return False
 		return len(self._cache) > self._threshold
 
+	def __getitem__(self, key):
+		return self.get(key)
+
+	def __setitem__(self, key, value):
+		return self.set(key, value)
+
+	def __delitem__(self, key):
+		return self.delete(key)
+
+	def __contains__(self, key):
+		return key in self._cache
+
 _cache = LessSimpleCache()
 
 def cached(timeout=5 * 60, key=lambda: "view:%s" % flask.request.path, unless=None, refreshif=None, unless_response=None):
@@ -358,6 +370,9 @@ def cached(timeout=5 * 60, key=lambda: "view:%s" % flask.request.path, unless=No
 
 	return decorator
 
+def is_in_cache(key=lambda: "view:%s" % flask.request.path):
+	return key() in _cache
+
 def cache_check_headers():
 	return "no-cache" in flask.request.cache_control or "no-cache" in flask.request.pragma
 

src/octoprint/server/views.py

@@ -9,7 +9,7 @@ import os
 import datetime
 
 from collections import defaultdict
-from flask import request, g, url_for, make_response, render_template, send_from_directory, redirect
+from flask import request, g, url_for, make_response, render_template, send_from_directory, redirect, abort
 
 import octoprint.plugin
 
@@ -20,6 +20,7 @@ from octoprint.settings import settings
 from octoprint.filemanager import get_all_extensions
 
 import re
+import base64
 
 from . import util
 
@@ -29,6 +30,17 @@ _logger = logging.getLogger(__name__)
 _valid_id_re = re.compile("[a-z_]+")
 _valid_div_re = re.compile("[a-zA-Z_-]+")
 
+@app.route("/cached.gif")
+def in_cache():
+	url = request.base_url.replace("/cached.gif", "/")
+	key = lambda: "view:{}:{}".format(url, g.locale.language if g.locale else "en")
+	if not util.flask.is_in_cache(key):
+		return abort(404)
+
+	response = make_response(bytes(base64.b64decode("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7")))
+	response.headers["Content-Type"] = "image/gif"
+	return response
+
 @app.route("/")
 @util.flask.preemptively_cached(cache=preemptiveCache,
                                 data=lambda: dict(path=request.path, base_url=request.url_root, query_string="l10n={}".format(g.locale.language) if g.locale else "en"),

src/octoprint/static/intermediary.html

@@ -153,20 +153,20 @@
                 if (baseUrl[baseUrl.length - 1] != "/") {
                     baseUrl += "/";
                 }
+                var indexCachedUrl = baseUrl + "cached.gif";
                 var serverOnlineUrl = baseUrl + "online.gif";
                 var backendOnlineUrl = baseUrl + "intermediary.gif";
 
                 var serverTimeout;
+                var cachedTimeout;
 
                 var message = window.document.getElementById("message");
 
-                var serverIsOnline = false;
-                var serverOnlineCallback = function(result) {
+                var indexCachedCallback = function(result) {
                     if (result == "load") {
-                        // our online.gif loaded, so the server is up, let's reload
-                        serverIsOnline = true;
+                        // our cached.gif loaded, so the index is cached now, let's reload
                         message.className = "pulsate1 green";
-                        message.innerText = "OctoPrint server online, reloading page...";
+                        message.innerText = "OctoPrint server ready, reloading page...";
 
                         var reloadUrl = baseUrl + currentQuery + currentFragment;
                         if (reloadUrl == window.location.href) {
@@ -175,7 +175,21 @@
                             window.location.href = reloadUrl;
                         }
                     } else {
-                        // online.gif still not available, let's look at
+                        // cached.gif still not available, let's look at it again in a second
+                        cachedTimeout = setTimeout(function() {
+                            ping(indexCachedUrl, timeout, indexCachedCallback);
+                        }, 1000)
+                    }
+                };
+
+                var serverIsOnline = false;
+                var serverOnlineCallback = function(result) {
+                    if (result == "load") {
+                        // our online.gif loaded, so the server is up, let's wait for it to become ready
+                        serverIsOnline = true;
+                        ping(indexCachedUrl, timeout, indexCachedCallback);
+                    } else {
+                        // online.gif still not available, let's look at it again later
                         var interval = 10;
                         if (intervals.length) {
                             interval = intervals.shift();
@@ -204,6 +218,9 @@
                         if (serverTimeout) {
                             window.clearTimeout(serverTimeout);
                         }
+                        if (cachedTimeout) {
+                            window.clearTimeout(cachedTimeout);
+                        }
 
                         message.className = "red";
                         message.innerHTML = "Looks like something went wrong during startup, the server is gone again. You should check <code>octoprint.log</code>.";