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Re: Load balancing and load determination


The only reason why I brought up the concept of a benchmark is because it is dead easy to provide the source for said benchmark and have backend servers simply time how long it takes to run it each status update. Each backend would simply then send the "time taken" and that would provide some measure of how beefy and/or loaded said server was.

The main consideration is one of consistency... unless there is some agreed upon "standard" then comparisons are worthless and the resulting load balancing will be inaccurate. For example, say that Apache is front-ending 10 servers, 5 are Apache and other 5 are Foo, but Foo consistently falsifies it's capability simply to ensure that it gets all the traffic. Sure, you can adjust settings on the front end to offset that, but that defeats the whole purpose of some *accurate*, objective measure of capability.

Yeah, I recall JR posting something after I brought up this topic at one of my ApacheCon sessions...

Maybe it's more of an "availability factor" than a load factor... with 0 being "send me nothing" and 1 being "I am completely unloaded" and decimal values between indicating their "availability" to handle traffic.

On Oct 30, 2018, at 9:06 AM, Daniel Ruggeri <DRuggeri@xxxxxxxxxxx> wrote:

Hi, Jim J;
I recall a while back that Jim Riggs proposed a spec for exactly this a while back... I think it was shared here on list and some light iteration was done. IIUC, he was even planning to present it at ACNA until travel plans fell through.

Hi, Jim R;
Any chance you have the latest and greatest, or is the version from the list archives current state?


One of the things I recall *really liking* from the recommendation is letting the backend decide its factor based on whatever it believes is most important. In some servers, that may be available threads. In others it could be percentage of memory used. Still yet, other servers may decide based on number of idle GPUs on-system. I think this is roughly the same you are suggesting, Jim J, but I struggle to think of a universal benchmark because backends are so varied.
--
Daniel Ruggeri

On October 30, 2018 7:53:20 AM CDT, Jim Jagielski <jim@xxxxxxxxxxx> wrote:
As some of you know, one of my passions and area of focus is
on the use of Apache httpd as a reverse proxy and, as such, load
balancing, failover, etc are of vital interest to me.

One topic which I have mulling over, off and on, has been the
idea of some sort of universal load number, that could be used
and agreed upon by web servers. Right now, the reverse proxy
"guesses" the load on the backend servers which is OK, and
works well enough, but it would be great if it actually "knew"
the current loads on those servers. I already have code that
shares basic architectural info, such as number of CPUs, available
memory, loadavg, etc which can help, of course, but again, all
this info can be used to *infer* the current status of those backend
servers; it doesn't really provide what the current load actually
*is*.

So I was thinking maybe some sort of small, simple and "fast"
benchmark which could be run by the backends as part of their
"status" update to the front-end reverse proxy server... something
that shows general capability at that point in time, like Hanoi or
something similar. Or maybe some hash function. Some simple code
that could be used to create that "universal" load number.

Thoughts? Ideas? Comments? Suggestions? :)