Issue 2432 - Cache browser versions during page generation

globals/get_browser_versions.py

 import re
 import os
 import sys
 import json
 import urllib2
 import errno
 import logging
 from xml.dom import minidom
 
 from jinja2 import contextfunction
 
 BROWSERS = {}
 
 CHROME_UPDATE_XML = '''\
 <?xml version="1.0" encoding="UTF-8"?>
 <request protocol="3.0" ismachine="0">
   <os platform="win" version="99" arch="x64"/>
   <app appid="{4DC8B4CA-1BDA-483E-B5FA-D3C12E15B62D}">
     <updatecheck/>
   </app>
   <app appid="{4DC8B4CA-1BDA-483E-B5FA-D3C12E15B62D}" ap="x64-beta-multi-chrome">
     <updatecheck/>
   </app>
   <app appid="{4DC8B4CA-1BDA-483E-B5FA-D3C12E15B62D}" ap="x64-dev-multi-chrome">
     <updatecheck/>
   </app>
 </request>'''
 
+cache = {}
+
 def get_mozilla_version(product, origin_version, channel,
                         minor=False, subdomain='aus4', origin_build='-',
                         attribute='appVersion', platform='WINNT_x86-msvc'):
   response = urllib2.urlopen('https://%s.mozilla.org/update/3/%s/%s/%s/%s/en-US/%s/-/default/default/update.xml?force=1' % (
     subdomain,
     product,
     origin_version,
     origin_build,
     platform,
     channel
@@ skipping 111 matching lines @@
     fd = os.open(filename, flags)
   except OSError as e:
     if e.errno != errno.ENOENT:
       raise
     os.makedirs(os.path.dirname(filename))
     fd = os.open(filename, flags)
   return os.fdopen(fd, 'w+')
 
 @contextfunction
 def get_browser_versions(context, browser):
+  versions = cache.get(browser)
+  if versions:
+    return versions
+
   func = BROWSERS[browser]
   exc_info = None
   try:
     versions = func()
   except Exception:
     exc_info = sys.exc_info()
 
   filename = os.path.join(context['source'].get_cache_dir(), 'browsers.json')
   with open_cache_file(filename) as file:
     try:
-      cache = json.load(file)
+      persistent_cache = json.load(file)
     except ValueError:
       if file.tell() > 0:
         raise
-      cache = {}
+      persistent_cache = {}
 
-    cached_versions = cache.get(browser)
+    cached_versions = persistent_cache.get(browser)
     if exc_info:
       if not cached_versions:
         raise exc_info[0], exc_info[1], exc_info[2]
 
       versions = cached_versions
       logging.warning('Failed to get %s versions, falling back to '
                       'cached versions', browser, exc_info=exc_info)
     else:
       # Determine previous version: If we recorded the version before and it
       # changed since then, the old current version becomes the new previous
       # version. If the version didn't change, use the cached previous version.
       current = versions['current']
       previous = None
       if cached_versions:
         cached_current = cached_versions['current']
         if cached_current != current:
           previous = cached_current
         else:
           previous = cached_versions['previous']
       versions['previous'] = previous
 
       # Remove duplicates from unreleased versions. Occasionally,
       # different channels are on the same version, but we want
       # to list each version only once.
       versions['unreleased'] = sorted(
         set(versions['unreleased']) - {current, previous},
         key=lambda ver: map(int, ver.split('.'))
       )
 
-      cache[browser] = versions
+      persistent_cache[browser] = versions
       file.seek(0)
-      json.dump(cache, file)
+      json.dump(persistent_cache, file)
       file.truncate()
 
   if not versions['previous']:
     logging.warning("Couldn't determine previous browser version, "
                     'please set %s.previous in %s', browser, filename)
 
+  cache[browser] = versions
   return versions