Re: Outbound HTTP throttling

 

I can say from personal experience that the F5 DevCentral site is the
place to go for irules. The folks there have been extremely helpful in
my challenges with irules. The site also keeps an archive of posts to
their boards that is extensive and easy to search. I can usually find
3-4 examples that are pretty close to what I am trying to accomplish.
Whatever I can't figure out myself, a post to their board is always
responded to quickly, usually within hours.

 

 

--

John LeMay

Systems Engineer

K. Hovnanian Companies LLC

Ph. 732 383-2195

 

From: [email protected] [mailto:[email protected]] On Behalf
Of Kelly Vista
Sent: Friday, May 08, 2009 4:13 PM
To: Load Balancing Mailing List
Subject: Re: [load balancing] Outbound HTTP throttling

 

Excellent feedback, thanks!  

First, thanks for pointing out the flaw in my post.  I didn't mention
that I would strongly prefer some sort of queue-ing.  Basically, I
imagine that a device would have some max number of connections it could
queue (assuming the client network timeout didn't kick in).  Even better
would be a "high availability" mode where multiple LBs, linked together,
share a common queue.  This ensures high availability and scalability,
although I don't know if the replication aspect of throttling is
feasible.  Returning connection reset or something else that would
require a retry would be an unfortunate reality.  So I'd prefer a queue.

We actually tried to work with F5 (we were comparing them against
NetScaler) but the whole process was pretty slow, unfortunately, and
also our IT folks were more familiar with NetScaler.  Among other
problems was that the F5 pre-sales folks didn't know where we would be
able to get a rule from.  They suggested the big F5 repository online,
but we couldn't find one very easily and we didn't want to spend money
learning the intricacies of rule writing only to find out what we were
doing was wrong.  Another problem was that we didn't know what the CPU
impact of rule execution might be.

If you can point me to a rule (or write it), I would be incredibly
indebted.   Based on this, I would recommend to management that we
pursue F5.

-- kv



On Fri, May 8, 2009 at 12:09 PM, Kirk Bauer <[email protected]> wrote:

This would be very easy to do with iRules on a BIG-IP.  If you have a
chance to try this out on a BIG-IP, let me know and I'll write a rule to
take care of it for you.

 

The way it would work is you direct the outbound traffic through a
virtual server (i.e. vip) on the BIG-IP and have a relatively
straight-forward iRule that would, for example, check the Host header
and keep track of the connections/sec for each separate destination
host.

 

The only question would be: what do you want to do once the threshold is
exceeded?  Do you want to delay the request until later, or do you want
to return some sort of retry status code to the server, etc?

 

From: [email protected] [mailto:[email protected]] On Behalf
Of Kelly Vista
Sent: Friday, May 08, 2009 11:30 AM
To: [email protected]
Subject: [load balancing] Outbound HTTP throttling

 

Hi -

At our company, we make use of a lot of "web APIs" that exist.  For
example, Google has a search API, Netflix has an API, etc.  Using these
APIs, we can create a lot of "mashups" or richly integrated data sets. 

However, we would like to be a "good Internet citizen" and obey the rate
limiting requirements of the sites we hit.  For example, many companies
have rate limiting policies like "no more than 5 requests per second".
Unfortunately, since we have many machines that - for several different
applications - hit these sites, we need to make sure that our
*aggregate* use is no more than 5 (or whatever) requests per second.

I'm writing to this list because I believe there may be load balancers
with L4 or L7 capabilities that allow us to do this and I was looking
for suggestions.  We are in the process of testing out Citrix NetScaler
for this and, although it seems somewhat capable, it's been very tricky
to configure.

To re-iterate the complexity of our particular problem, it has to do
with rate limiting outbound traffic based on number of
connections/requests per second.

If anyone has any insight into solutions that do this (h/w or s/w), I
would appreciate it.

For the record, I know there are software solutions like like Apache
mod_throttle and mod_cband, Linux iptables, Squid, Vista Server QoS,
etc.  I'm open to any of these provided it's straightfoward to manage.
I would prefer the reliability of solid state, but my first priority is
any kind of solution, reliability can be an "optimization".

Thanks for any and all help,
--kv


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