[Twisted-web] html cache with timeout

[Valentino Volonghi aka Dialtone]

On Tue, 01 Feb 2005 12:58:49 GMT, Valentino Volonghi aka Dialtone <dialtone at divmod.com> wrote:

The first version of the patch didn't actually work. But I wrote a new version, also thanks to fzZzy and this time it works although it has a flaw since in weever caching the content slot (which is filled with a Fragment) results in 2 big red Nones and the rendered fragment.

As I said in the first mail you can use caching with:

t.cached(name=some_sensible_name, lifetime=MAX_LIFE)[cached_content]

This patch provides, probably, the finest granularity in caching the rendering.

Anyway the patch is below:

Index: nevow/tags.py
===================================================================
--- nevow/tags.py       (revision 1136)
+++ nevow/tags.py       (working copy)
@@ -25,7 +25,7 @@
 """
 
 
-from nevow.stan import Proto, Tag, directive, raw, xml, CommentProto, invisible, slot, cdata
+from nevow.stan import Proto, Tag, directive, raw, xml, CommentProto, invisible, slot, cdata, cached
 
 
 comment = CommentProto()
@@ -62,7 +62,9 @@
 def inlineJS(s):
     return script(type="text/javascript", language="JavaScript")[xml('\n//<![CDATA[\n%s\n//]]>\n' % s)]
 
-__all__ = tags + ['invisible', 'comment', '_dir', '_del', '_object', '_map', 'drange', 'Tag', 'directive', 'xml', 'raw', 'slot', 'cdata', 'inlineJS'] + ['_%s' % x for x in range(100)]
+__all__ = tags + ['invisible', 'comment', '_dir', '_del', '_object',
+                  '_map', 'drange', 'Tag', 'directive', 'xml', 'raw',
+                  'slot', 'cached', 'cdata', 'inlineJS'] + ['_%s' % x for x in range(100)]
 
 
 ########################
Index: nevow/flat/flatstan.py
===================================================================
--- nevow/flat/flatstan.py      (revision 1136)
+++ nevow/flat/flatstan.py      (working copy)
@@ -9,7 +9,7 @@
 from nevow import util
 from nevow.stan import Proto, Tag, xml, directive, Unset, invisible
 from nevow.inevow import IRenderer, IRendererFactory, IGettable, IData
-from nevow.flat import precompile, serialize
+from nevow.flat import precompile, serialize, iterflatten
 from nevow.accessors import convertToData
 from nevow.context import WovenContext
 
@@ -226,6 +226,56 @@
         return serialize(original.default, context)
     return serialize(data, context)
 
+_CACHE = {}
+from time import time as now
+from cStringIO import StringIO
+from twisted.internet import defer
+def CachedSerializer(original, context):
+    cached = _CACHE.get(original.name, None)
+    life = now()-original.lifetime
+    if cached and cached[0] > life:
+##         print "="*20
+##         print cached[0]
+##         print life
+##         print "="*20        
+        yield cached[1]
+        return
+##     if cached:
+##         print "="*20
+##         print cached[0]
+##         print life
+##         print "="*20
+    io = StringIO()
+    for child in iterflatten(original.children, context, io.write,
+                             lambda item: True):
+        if isinstance(child, tuple):
+            childDeferred, childReturner = child
+ 
+            d = defer.Deferred() ## A new deferred for the outer loop, whose result
+            ## we don't care about, because we don't want the outer loop to write
+            ## anything when this deferred fires -- only when the entire for loop
+            ## has completed and we have all the "children" flattened
+ 
+            def innerDeferredResultAvailable(result):
+                childReturner(result) ## Cause the inner iterflatten to continue
+                d.callback('') ## Cause the outer iterflatten to continue
+                return ''
+ 
+            childDeferred.addCallback(innerDeferredResultAvailable)
+ 
+            ## Make the outer loop wait on our new deferred.
+            ## We call the new deferred back with ''
+            ## Which will cause the outer loop to write '' to the request,
+            ## which doesn't matter. It will then call our "returner",
+            ## which is just the noop lambda below, because we don't care
+            ## about the return result of the new deferred, which is just
+            ## ''
+ 
+            yield d, lambda result: None    
+    result = io.getvalue()
+    _CACHE[original.name] = (now(), result)
+    yield result
+
 def ContextSerializer(original, context):
     originalContext = original.clone(deep=False)
     originalContext.precompile = context and context.precompile or False
Index: nevow/__init__.py
===================================================================
--- nevow/__init__.py   (revision 1136)
+++ nevow/__init__.py   (working copy)
@@ -182,6 +182,7 @@
 nevow.flat.flatstan.RendererSerializer            nevow.inevow.IRenderer
 nevow.flat.flatstan.DirectiveSerializer           nevow.stan.directive
 nevow.flat.flatstan.SlotSerializer                nevow.stan.slot
+nevow.flat.flatstan.CachedSerializer              nevow.stan.cached 
 nevow.flat.flatstan.ContextSerializer             nevow.context.WovenContext
 nevow.flat.flatstan.DeferredSerializer            twisted.internet.defer.Deferred
 nevow.flat.flatstan.DeferredSerializer            twisted.internet.defer.DeferredList
Index: nevow/stan.py
===================================================================
--- nevow/stan.py       (revision 1136)
+++ nevow/stan.py       (working copy)
@@ -119,8 +119,33 @@
         """
         raise NotImplementedError, "Stan slot instances are not iterable."
 
+class cached(object):
+    """Marker for cached content
+    """
+    __slots__ = ['name', 'children', 'lifetime']
 
+    def __init__(self, name, lifetime=0):
+        self.name = name
+        self.children = []
+        self.lifetime = lifetime
 
+    def __repr__(self):
+        return "cached('%s','%s')" % self.name, self.lifetime
+
+    def __getitem__(self, children):
+        """cached content is what is being cached
+        """
+        if not isinstance(children, (list, tuple)):
+            children = [children]
+        self.children.extend(children)
+        return self
+
+    def __iter__(self):
+        """Prevent an infinite loop if someone tries to do
+            for x in cached('foo'):
+        """
+        raise NotImplementedError, "Stan slot instances are not iterable."
+
 class Tag(object):
     """Tag instances represent XML tags with a tag name, attributes,
     and children. Tag instances can be constructed using the Prototype