JMeter

Jun. 9th, 2015

Using IP Spoofing to Simulate Requests from Different IP Addresses with JMeter

It’s not easy today to find a single node system as both failover and resilience are key points of modern applications. So if you need to load test a system, it will likely be something clustered.

The idea of a cluster is to protect the application from failure. If one node goes out of order, the remaining ones will continue to serve incoming requests. Usually hardware or software load balancers act as a single entry point, orchestrating all the incoming requests and sending them to the appropriate backend servers.

We have already covered the situation when the load balancer has more than one IP address and we know how to configure JMeter to hit all the load balancer endpoints. If it is something you missed you’re very welcome to read The DNS Cache Manager: The Right Way To Test Load Balanced Apps guide. 

The Challenge of Stickiness

One of the main features of load balancers is “stickiness” or “persistence” - a mechanism of wiring a client to one backend node behind the load balancer so requests could go back and forth. For example, if the application uses cookie-based authentication and the user has logged into one of the backend nodes, he will be authenticated there only for the amount of time required to replicate the session cache (which may be not immediate). This is one reason for stickiness.

As simulated by JMeter the request goes via the Load Balancer, hits Server A and gets a Cookie. If the following request will go to the Server B it will not be authenticated as for the moment only Server A knows about this user and accepts its Cookie unless local caches are replicated into a Shared Cache.

https://www.blazemeter.com/blog/using-ip-spoofing-simulate-requests-different-ip-addresses-jmeter