From f76950896a64bd5012fe490ba546a1be3a9f4a56 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20P=C3=A9ters?= <fpeters@entrouvert.com>
Date: Wed, 18 Nov 2015 12:22:03 +0100
Subject: [PATCH] misc: add a new statics_hash in context variables (#8875)

This variable is to be used to prevent browser using stale resources
(javascript and stylesheets) after package upgrades.

Use it like href="{% static 'foobar.css' %}?{{statics_hash}}".

It is computed from installed module versions + the access time of
settings.STATICS_HASH_COUNTER (so it's possible to "force" a reload by touching
that file).

Set settings.STATICS_HASH_COUNTER to /var/lib/publik/statics-counter in the
debian packaging.
---
 debian/debian_config_common.py |  2 ++
 hobo/__init__.py               |  3 +++
 hobo/context_processors.py     | 18 ++++++++++++++++--
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/debian/debian_config_common.py b/debian/debian_config_common.py
index 66074bd..3c4384a 100644
--- a/debian/debian_config_common.py
+++ b/debian/debian_config_common.py
@@ -194,3 +194,5 @@ USE_TZ = True
 # Celery configuration
 BROKER_URL = 'amqp://'
 BROKER_TASK_EXPIRES = 120
+
+STATICS_HASH_COUNTER = '/var/lib/publik/statics-counter'
diff --git a/hobo/__init__.py b/hobo/__init__.py
index e69de29..33635e5 100644
--- a/hobo/__init__.py
+++ b/hobo/__init__.py
@@ -0,0 +1,3 @@
+# import the context_processors module so it gets to compute the versions hash
+# early on.
+from . import context_processors
diff --git a/hobo/context_processors.py b/hobo/context_processors.py
index 85c1a5f..31bb8ba 100644
--- a/hobo/context_processors.py
+++ b/hobo/context_processors.py
@@ -3,18 +3,32 @@ import hashlib
 import logging
 import requests
 import threading
+import os
 import urlparse
 
 from django.conf import settings
 from django.core.cache import cache
 from django.template import Template
 
-def template_vars(request):
-    return getattr(settings, 'TEMPLATE_VARS', {})
+from hobo.scrutiny.wsgi.middleware import VersionMiddleware
 
 logger = logging.getLogger('hobo')
 
 CACHE_REFRESH_TIMEOUT = 300
+VERSIONS = VersionMiddleware.get_packages_version()
+
+
+def template_vars(request):
+    statics_hash = hashlib.md5(repr(sorted(VERSIONS.items())))
+    try:
+        counter_filename = getattr(settings, 'STATICS_HASH_COUNTER', None)
+        if counter_filename:
+            statics_hash.update(str(os.stat(counter_filename).st_atime))
+    except OSError:
+        pass
+    template_vars = getattr(settings, 'TEMPLATE_VARS', {})
+    template_vars.update({'statics_hash': statics_hash.hexdigest()})
+    return template_vars
 
 class RemoteTemplate(object):
     def __init__(self, source):
-- 
2.6.2