Gatling reports incorrect performance results for Websocket app

Gatling (Open-Source)
1

Using Gatling 2.1.7 to test performance of our application.
Scenario:

  1. app send the query
  2. server starts responding with partial data every few seconds
  3. after some time server sends complete dataset, which has “completion”:1.0,“data”

So, when I do these steps manually (In Chrome WebSocket app), I’m see, that query is completed in 28 seconds:

http://slavikca.myds.me/Files/forums/direct.txt

But when I do same thing in Gatling, I’m getting 198 seconds:
http://slavikca.myds.me/Files/forums/gatling.txt

Here is part of the script:

  val completeString:String = """.*"completion":1\.0,"data":.*"""

  val httpConf = http
    .wsBaseURL(endpoint)

  val scn = scenario("WebSocket")
    .exec(ws("Connect WS").open(""))
    .exec(ws("Sending query")
           .sendText(session => optimizeQuery())
           .check(wsAwait.within(300).until(1).regex(completeString).saveAs("SiftOutput"))
    )
    .exec{ session =>
        session("SiftOutput").asOption[String].foreach(println)
        session
        }
    .exec(ws("Close WS").close)

  //setUp(scn.inject(rampUsers(users) over (2 seconds)).protocols(httpConf))
  setUp(scn.inject(atOnceUsers(1)).protocols(httpConf))
}

Why results would be so wrong in Gatling?

2

The run above has WebSocket timeout.

So, I repeated steps with smaller query.
And got same results, but without timeout:
18 Seconds for manual tests:

http://slavikca.myds.me/Files/forums/direct2.txt

But when I do same thing in Gatling, I’m getting 88 seconds:
http://slavikca.myds.me/Files/forums/gatling2.txt

3

No idea. Would need to be able to get my hands on a reproducer to be able to investigate.