On 6 Sep, 11:59 pm, [EMAIL PROTECTED] wrote:
I'd like to start streaming the document as soon as I start receiving
the results of the operation, but I'm stumped on how to actually
implement this. If I return a deferred from the render method, I cannot
fire this deferred until all of the rows have been built up.
Use a recursive generator that yields Deferreds for loading each row.
Here's an example - which I even looked at in a web browser :) - that
should help to get you started. (The athena stuff is beside the point,
it's just the quickest way I know to get a server serving a Nevow
page...)
Warning: I haven't tested this on really large datasets, so it might
have disastrous performance consequences. I don't *think* that it will,
but I know there are some booby-traps in the rendering pipeline to snare
the unwary.
# -- cut here for slow.py --
# Run quickly: twistd -n athena-widget --element slow.SlowElement
from twisted.internet import defer
from twisted.internet import reactor
from nevow.loaders import stan
from nevow.tags import div, directive
from nevow.athena import LiveElement
from nevow.page import renderer
def deferLater(n, result=None):
"""
Why isn't this in Twisted yet? Is it?
"""
d = defer.Deferred()
reactor.callLater(n, d.callback, result)
return d
def delayedResults(results):
"""
Yield results.... slowly.....
"""
yield div[results.pop(0)]
if results:
def more(result):
return delayedResults(results)
yield deferLater(2.0).addCallback(more)
class SlowElement(LiveElement):
"""
Render a list of 1 to 10 really slowly.
"""
def start(self, ctx, data):
"""
Give some data, wait for next result...
"""
return delayedResults(map(str,range(10)))
renderer(start)
docFactory = stan(div(render=directive("start")))
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