On Wed, 11 Jul 2012 00:52:06 +0200, Ian Hickson <[email protected]> wrote:
On Tue, 10 Jul 2012, Kornel Lesi�~Dski wrote:
However, I'm afraid that the most common implementation (aside from
complete lack of error recovery) will be a simple as 30-second retry
interval and that won't be very DoS-safe. UAs can do better than that.
That's not entirely clear.
It would seem below that you are providing reasons why UAs can do better
than that, and better than individual authors (apart from the question of
whether it is better to have a couple of dozen UAs write the code, or
every app developer do so)...
For example the spec could require UAs to have randomized retry interval
and exponential backoff on failure. Is there anything more that authors
could do client-side to avoid DoSing?
Exponential back-off isn't at all necessarily the right solution. In
particular, consider mobile devices, where network connectivity goes in
and out as the user moves. Most of the time, you want to be trying to
connect as soon as you have connectivity. Similarly with laptops on wifi
where the connection is only briefly hurt by an obstacle -- you want to
keep trying every few seconds until the obstacle is gone. Exponential
backoff if a terrible thing in those kinds of situations.
You can distinguish local network difficulties from server load
difficulties in a variety of ways, e.g. having a dedicated ping server on
the same network as the "real" server, which doesn't suffer from the same
load concerns, and which you try to contact and only switch to
exponential backoff if it responds but the main server isn't. And so on.
UAs can do that kind of thing.
SSE is mostly a convenience API (advanced authors can use streaming XHR
or WebSockets to achieve the same result the hard way), so lack of
convenience in error recovery feels like an omission in this API.
If it's something we do want to eventually support, I think it's be
something to consider for v2.
I think it is something to consider as a bug in v1 - UAs can decide to
fail eventually, but a single dropped connection seems like a poor reason
to do so given the still somewhat flaky network we have around the world
today. Living in Western European capitals with relatively good
infrastructure, I find simple network dropout on fixed "broadband"
networks far more common that something like entering a tunnel.
cheers
Chaals
--
Chaals - standards declaimer
