On Tue, 5 Oct 2010, Michael Schnell wrote:
On 10/01/2010 05:11 PM, Michael Van Canneyt wrote:
Define excessive polling ?
IMHO, any "dump" polling is excessive. IMHO, a decent method needs to "sleep"
most of the time in a polling cycle (not generating CPU or network traffic)
and the asynchronous event needs to "wake" the process. This is the only way
to provide both low latency and low overhead.
I thought like you, 12 years ago. Till reality kicked in. Faulty switches,
company firewalls and whatnot. Not all servers/firewalls support HTTP 1.1
(for a persistent connection) etc. Too many problems.
Yep ! HTTP is essentially not suitable for this. You would be much better off
using normal bidirectional TCP/IP communication. It's only because of the
dump IP departments that this silly http add-ons are necessary.
Even so, we use TCP/IP communication: same problems. Faulty firewalls and
switches. I suspect that in 25% of cases, things go wrong if you work over
internet. Hardly noticeable for HTTP with its small requests (and of course
all ISPs make sure HTTP traffic gets priority) but a major mess if you use
regular TCP/IP. You're better off with UDP these days.
Things may be better on intranets, but for internet persistent connections
are a faraway dream. We had to spend lots of time on a
error-detection + reconnect scheme to work around all problems.
Michael.
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