Matthew Morgan wrote:
On Wed, Nov 25, 2009 at 7:09 PM, Amos Jeffries <squ...@treenet.co.nz> wrote:
Matthew Morgan wrote:
Sorry it's taking me so long to get this done, but I do have a question.
You suggested making getRangeOffsetLimit a member of HttpReply. There are
two places where this method currently needs to be called: one is
CheckQuickAbort2() in store_client.cc. This one will be easy, as I can just
do entry->getReply()->getRangeOffsetLimit().
The other is HttpStateData::decideIfWeDoRanges in http.cc. Here, all we
have access to is an HttpRequest object. I looked through the source to see
if I could find where a request owned or had access to a reply, but I don't
see anything like that. If getRangeOffsetLimit were a member of HttpReply,
what do you suggest doing here? I could make a static version of the
method, but that wouldn't allow caching the result.
Ah. I see. Quite right.
After a bit more though I find my original request a bit weird.
Yes it should be a _Request_ member and do its caching there. You can go
ahead with that now while we discuss whether to do a slight tweak on top of
the basic feature.
[cc'ing squid-dev so others can provide input]
I'm not certain of the behavior we want here if we do open the ACLs to reply
details. Some discussion is in order.
Simple way would be to not cache the lookup the first time when reply
details are not provided.
It would mean making it return potentially two different values across the
transaction.
1) based on only request detail to
and other on request+reply details. decide if a range request to possible.
and then
2) based on additional reply details to see if the abort could be done.
No problem if the reply details cause an increase in the limit. But if they
restrict it we enter grounds of potentially making a request then canceling
it and being unable to store the results.
Or, taking the maximum of the two across two calls? so it can only increase.
would be slightly trickier involving a flag a well to short-circuit the
reply lookups instead of just a magic cache value.
Am I seriously over-thinking things today?
Amos
Here's a question, too: is this feature going to benefit anyone? I
realized later that it will not solve my problem, because all the
traffic that was getting force downloaded ended up being from windows
updates. The urls showing up in netstat and such were just weird
because the windows update traffic was actually coming from limelight.
My ultimate solution was to write a script that reads access.log,
checks for windows update urls that are not cached, and manually
download them one at a time after hours.
If there is anyone at all who would benefit from this I would still be
*more* than glad to code it (as I said, it would be my first real open
source contribution...very exciting), but I just wondered if anyone
will actually use it.
I believe people will find more control here useful.
Windows update service packs are a big reason, but there are also
similar range issues with Adobe Reader online PDFs, google maps/earth,
and flash videos when paused/resumed. Potentially other stuff, but I
have not heard of problems.
This will allow anyone to fine tune the places where ranges are
permitted or forced to fully cache. Avoiding the problems a blanket
limit adds.
As to which approach would be better, I don't know enough about that
data path to really suggest. When I initially made my changes, I just
replaced each reference to Config.range_offset_limit or whatever.
Today I went back and read some more of the code, but I'm still
figuring it out. How often would the limit change based on the
request vs. the reply?
Just the once. On first time being checked for the reply.
And most likely on the case of testing for a reply mime type. The other
useful info I can think of are all request data.
You can ignore if you like. I'm just worrying over a borderline case.
Someone else can code a fix if they find it a problem or need to do mime
checks.
Amos
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