jinja2_template.py: Compile the same source only once and use compiled source next time.

compile function takes a lot of time, thus this change saves time when the same source is used many times in apache frontend SR.

slapos/recipe/template/jinja2_template.py

@@ -155,6 +155,7 @@ def get_umask():
     get_umask = lambda: umask
     return umask
 
+compiled_source_cache = {}
 class Recipe(object):
 
     def __init__(self, buildout, name, options):
@@ -223,8 +224,18 @@ class Recipe(object):
             with open(template, 'rb') as f:
                 source = f.read().decode(self.encoding)
         env = self.env
+
+        # get compiled source
+        if template == '<inline>':
+          compiled_source = env.compile(source, filename=template)
+        else:
+          try:
+            compiled_source = compiled_source_cache[template]
+          except KeyError:
+            compiled_source_cache[template] = compiled_source = env.compile(source, filename=template)
+
         template = env.template_class.from_code(env,
-            env.compile(source, filename=template),
+            compiled_source,
             env.make_globals(None), None)
         rendered = template.render(**self.context).encode(self.encoding)
         mode = self.mode