Re: Outbound HTTP throttling

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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