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From Peter Schuller <>
Subject Re: non blocking Cassandra with Tornado
Date Tue, 27 Jul 2010 15:44:20 GMT
> The idea is rather than calling a cassandra client function like
> get_slice(), call the send_get_slice() then have a non blocking wait on the
> socket thrift is using, then call recv_get_slice().

(disclaimer: I've never used tornado)

Without looking at the generated thrift code, this sounds dangerous.
What happens if send_get_slice() blocks? What happens if
recv_get_slice() has to block because you didn't happen to receive the
response in one packet?

Normally you're either doing blocking code or callback oriented
reactive code. It sounds like you're trying to use blocking calls in a
non-blocking context under the assumption that readable data on the
socket means the entire response is readable, and that the socket
being writable means that the entire request can be written without
blocking. This might seems to work and you may not block, or block
only briefly. Until, for example, a TCP connection stalls and your
entire event loop hangs due to a blocking read.

Apologies if I'm misunderstanding what you're trying to do.

/ Peter Schuller

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