Nick Johnson (Google) wrote:
Hi Peter,
The simultaneous dynamic request limit was eliminated in a recent SDK.
It has been replaced with the flexible provisioning system detailed in
the FAQ entry you quote.
It's correct that as long as you keep your latencies low, you should
never run into any sort of request limit.
What happens if most requests are fast (< 1 second), but some are slower
(let's say 10% of all requests), because they use urlfetch calls and
have to wait for the answer (could be up to 5 seconds). Will the system
automatically detect that these are requests that are just waiting (and
doing nothing else)?
-Ulrich
-Nick Johnson
On Sat, Apr 10, 2010 at 2:12 PM, peterk <[email protected]
<mailto:[email protected]>> wrote:
I've been using and watching appengine since, well, the beginning, and
only by a random Google about an unrelated topic did I find out about
this notion of a cap on 'simultaneous active requests'. I came across
discussions where people were saying that there is a cap of 30
simultaneous active requests, citing the Quota page and so on.
But when I go to the Quota page - there's not a single mention of any
such limit. Why not? Has something changed?
Reading the quotas on that page it's easy to conclude - naively
perhaps in hindsight - that 500 requests/second is 500 requests/second
irrespective of the average execution time of those requests.
There is no mention of any assumption on that page about the time
taken to serve a request or anything else that goes into the
calculation for 500 requests/second.
After some further searching I finally found mention of this limit in
the FAQs, but here it's still quite vague - and again, no specific
mention of this 30 simultaneous request limit. It says:
"However, App Engine reserves automatic scaling capacity for
applications with low latency, where the application responds to
requests in less than one second. Applications with very high latency
(over one second per request for many requests) are limited by the
system, and require a special exemption in order to have a large
number of simultaneous dynamic requests. If your application has a
strong need for a high throughput of long-running requests, you can
request an exemption from the simultaneous dynamic request limit. The
vast majority of applications do not require any exemption."
Which doesn't imply a hard limit, but rather that as long as your
(average?) request fulfilment time is below one second you shouldn't
have to worry about this. To be very exacting, if I keep my average
request time under 1 second I should *never* see an error relating to
this cap? This is a bit different than the talk of 30 simultaneous
requests max - at that level with the max of 500 requests a second,
you'd be limited to an average request time of 60ms!
So what is the story here? Why is this all being talked about in the
shadows of message boards with no clear policy? Why isn't this
limitation in the quota page? I thought I had GAE all figured out but
then this ball gets thrown into the mix out of left field.
--
You received this message because you are subscribed to the Google
Groups "Google App Engine" group.
To post to this group, send email to
[email protected]
<mailto:[email protected]>.
To unsubscribe from this group, send email to
[email protected]
<mailto:google-appengine%[email protected]>.
For more options, visit this group at
http://groups.google.com/group/google-appengine?hl=en.
--
Nick Johnson, Developer Programs Engineer, App Engine Google Ireland
Ltd. :: Registered in Dublin, Ireland, Registration Number: 368047
Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration
Number: 368047
--
You received this message because you are subscribed to the Google
Groups "Google App Engine" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/google-appengine?hl=en.
--
You received this message because you are subscribed to the Google Groups "Google
App Engine" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/google-appengine?hl=en.
