[Twisted-Python] Re: flow.Zip
lafou at wanadoo.fr
Wed Apr 23 11:36:16 EDT 2003
> Well, Cooperate is the whole reason for flow... otherwise you
> could just use recursive generators. Basically, in one of
> your generators (Threaded(QueryIterator())), your code would
> block waiting for a row, etc. So rather than blocking, Threaded
> returns Cooperate. This return value is handled by the wrappers
> all the way up the call chain. At the top of the call chain is
> Deferred, and when Deferrerd gets a Cooperate, it does a
> callLater(0, self), so that other processes can run.
> Suppose you have generator X -> Y -> Z, the picture
> then looks like...
> Wrap <-- Z
> Wrap <--> Y
> Wrap <--> X
> So, rather than X talking to Y, talking to Z, each of
> your generators is talking to a wrapper instead, which
> tries to be as transparent as possible. The
> wrapper has the following behavior:
> 0. If a value is returned from a generator to
> a wrapper, it is given to the previous generator
> in the chain; at the bottom of the chain it is
> added to an array which is sent to the deferred's
> callback. Failures are handled the same way.
> 1. If the value returned is a wrapper, then it adds
> the new wrapper to the top of the stack and
> starts to process it.
> 2. When Cooperate is returned from a generator,
> it is sent all the way down the Wrapper linked
> list so that the reactor can re-schedule the
> processing chain (micro-thread).
> So, I hope this helps. Cooperate is the whole reason
> for flow... without the need to 'pause' the whole stack
> one wouldn't need the wrapper at all.
> ;) Clark
Ho, this makes more sence now. Thank you ! (Maybe you could insert this in flow.py inline
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