Patch to Google Course Builder v1.5.0, adding caching of the bytecode of Jinja2 templates. Change to the root dir of your course builder installation and use patch -p2 < (this file). Version 1.5.1 will probably include this patch.

coursebuilder-bytecodecache-1.5.0.patch

diff --git a/coursebuilder/common/jinja_utils.py b/coursebuilder/common/jinja_utils.py
index 9854a44..a5501e0 100644
--- a/coursebuilder/common/jinja_utils.py
+++ b/coursebuilder/common/jinja_utils.py
@@ -18,8 +18,10 @@ __author__ = 'John Orr ([email protected])'
 
 import jinja2
 from webapp2_extras import i18n
+from models.models import MemcacheManager
 import safe_dom
 import tags
+from jinja2.bccache import BytecodeCache
 
 
 def finalize(x):
@@ -61,12 +63,68 @@ def get_gcb_tags_filter(handler):
     return gcb_tags
 
 
+class ClearableMemcachedBytecodeCache(BytecodeCache):
+    """Requires a fancy memcache client, like Google App Engine's,
+    that supports namespaces.  Requires get, set, add, and incr.
+
+    When you call .clear(), the entries previously stored through
+    this object become inaccessible through it, although they
+    are not guaranteed to be evicted from the underlying memcached
+    immediately.
+    """
+
+    def __init__(self, client, namespace=None,
+            prefix='jinja2:bytecode:', timeout=None,
+            ignore_memcache_errors=True):
+        self.namespace = namespace
+        self.client = client
+        self.prefix = prefix
+        self.timeout = timeout
+        self.ignore_memcache_errors = ignore_memcache_errors
+
+    def _get_key(self, bucket):
+        generation_key = self.prefix + '__generation__'
+        generation = '1'
+        if not self.client.add(generation_key, generation, namespace=self.namespace):
+            generation = self.client.get(generation_key,
+                    namespace=self.namespace)
+
+        return '%s:%s:%s' % (self.prefix, generation, bucket.key)
+
+    def clear(self):
+        generation_key = self.prefix + '__generation__'
+        if not self.client.incr(generation_key, 1, namespace=self.namespace):
+            self.client.set(generation_key, '1', namespace=self.namespace)
+
+    def load_bytecode(self, bucket):
+        try:
+            code = self.client.get(self._get_key(bucket),
+                namespace=self.namespace)
+        except Exception:
+            if not self.ignore_memcache_errors:
+                raise
+            code = None
+        if code is not None:
+            bucket.bytecode_from_string(code)
+
+    def dump_bytecode(self, bucket):
+        args = (self._get_key(bucket), bucket.bytecode_to_string())
+        if self.timeout is not None:
+            args += (self.timeout,)
+        try:
+            self.client.set(*args, namespace=self.namespace)
+        except Exception:
+            if not self.ignore_memcache_errors:
+                raise
+
+
 def get_template(template_name, dirs, locale=None, handler=None):
     """Sets up an environment and gets jinja template."""
 
     jinja_environment = jinja2.Environment(
         autoescape=True, finalize=finalize,
         extensions=['jinja2.ext.i18n'],
+        bytecode_cache=ClearableMemcachedBytecodeCache(MemcacheManager),
         loader=jinja2.FileSystemLoader(dirs))
     jinja_environment.filters['js_string'] = js_string
     jinja_environment.filters['gcb_tags'] = get_gcb_tags_filter(handler)
diff --git a/coursebuilder/models/models.py b/coursebuilder/models/models.py
index 81e02ec..b5fe999 100644
--- a/coursebuilder/models/models.py
+++ b/coursebuilder/models/models.py
@@ -100,6 +100,14 @@ class MemcacheManager(object):
                 key, value, ttl, namespace=cls._get_namespace(namespace))
 
     @classmethod
+    def add(cls, key, value, ttl=DEFAULT_CACHE_TTL_SECS, namespace=None):
+        """Adds an item in memcache if memcache is enabled."""
+        if CAN_USE_MEMCACHE.value:
+            CACHE_PUT.inc()
+            return memcache.add(
+                key, value, ttl, namespace=cls._get_namespace(namespace))
+
+    @classmethod
     def delete(cls, key, namespace=None):
         """Deletes an item from memcache if memcache is enabled."""
         if CAN_USE_MEMCACHE.value:
@@ -110,7 +118,7 @@ class MemcacheManager(object):
     def incr(cls, key, delta, namespace=None):
         """Incr an item in memcache if memcache is enabled."""
         if CAN_USE_MEMCACHE.value:
-            memcache.incr(
+            return memcache.incr(
                 key, delta,
                 namespace=cls._get_namespace(namespace), initial_value=0)
 
diff --git a/coursebuilder/models/vfs.py b/coursebuilder/models/vfs.py
index 648fc56..ff95c84 100644
--- a/coursebuilder/models/vfs.py
+++ b/coursebuilder/models/vfs.py
@@ -156,6 +156,8 @@ class LocalReadOnlyFileSystem(object):
         jinja_environment = jinja2.Environment(
             autoescape=True, finalize=jinja_utils.finalize,
             extensions=['jinja2.ext.i18n'],
+            bytecode_cache=jinja_utils.ClearableMemcachedBytecodeCache(
+                MemcacheManager),
             loader=jinja2.FileSystemLoader(physical_dir_names))
         jinja_environment.filters['js_string'] = jinja_utils.js_string
 
@@ -511,6 +513,8 @@ class DatastoreBackedFileSystem(object):
         jinja_environment = jinja2.Environment(
             autoescape=True, finalize=jinja_utils.finalize,
             extensions=['jinja2.ext.i18n'],
+            bytecode_cache=jinja_utils.ClearableMemcachedBytecodeCache(
+                MemcacheManager, namespace=self._ns),
             loader=VirtualFileSystemTemplateLoader(
                 self, self._logical_home_folder, dir_names))
         jinja_environment.filters['js_string'] = jinja_utils.js_string