Jmeter http requests get 400 response code in some random thread

Question

I wrote an test plan by using JMeter. it's structured like this:

Thread Group

• HTTP Cache Manager
• HTTP Cookie Manager
• CSV Data Set Config
• CSV Data Set Config
• Index Page
  • a few Http requests
• Random Order Controller
  • a few Http requests
• login page
  • a few Http requests
  • Random Order Controller
  • a few Http requests
  • Throughput Controller
  • a few Http requests
• Simple Controller
  • a few Http requests
• View Results Tree

I run 50 threads, however, some random http request fails with "Response code:400" in a thread, but it's successful for in other threads.

So I'm don't know how to investigate on this, as it works fine sometimes but it fails once or twice.

Can anyone give me some suggestions? I will really appreciate with your help.

Answer 1

you're possibly over hitting it with 50 threads (wild guess) Gateway Timeout perhaps .

Look at http://w3.org/Protocols/rfc2616/rfc2616-sec10.html

Note to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out

if decreasing number of threads eliminates issue than it's not a test issue it's elsewhere.

Resolution details from the user1488025 :

We found the bug in mod_jk. Basically the default configuration of mod_jk doesn't work under high load, it will become slow, unresponsive, causes http error and half closed connections over time.