Gatling j.n.ConnectException: Address already in use

Question

When running simulations with Gatling I get the following exceptions:

j.n.ConnectException: Address already in use: no further information

Does this occur when the server tested against fails to respond or timeout? I want to make sure this is a exception thrown by the server and not by the client.

Answer 1

I also encountered this problem running Gatling (with a lot of requests, > 100 RPS) on Windows. It seems Windows is running out of ephemeral ports to use. See this discussion in the user group forum. So this is not a problem with your system under test, but with the machine running Gatling.

On Windows, you can see and change your ephemeral port range using the netsh command. You can use following commands to

• see your currently configured IPv4 port range for TCP:

  netsh int ipv4 show dynamicport tcp
  

• change the port range:

  netsh int ipv4 set dynamic tcp start=number num=range
  

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E.g., I increased my ephemeral IPv4 TCP port range like so to resolve the problem:

netsh int ipv4 set dynamic tcp start=1025 num=57975