# simulation set up

**URL:** <https://community.gatling.io/t/simulation-set-up/3021>\
**Category:** Gatling (Open-Source)\
**Created:** [May 23, 2016, 6:12am UTC](https://community.gatling.io/t/simulation-set-up/3021 "2016-05-23T06:12:51Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Minh](https://avatars.discourse-cdn.com/v4/letter/m/53a042/32.png) [@Minh](https://community.gatling.io/u/Minh)\
**Post date:** [May 23, 2016, 6:12am UTC](https://community.gatling.io/t/simulation-set-up/3021/1 "2016-05-23T06:12:51Z")

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Hi Gatling Experts

With the sample of the simulation following we inject one user at once :

class BasicSimulation extends Simulation {

val httpConf = http  
.baseURL(“[http://computer-database.gatling.io](http://computer-database.gatling.io)”)  
.acceptHeader(“text/html,application/xhtml+xml,application/xml;q=0.9,_/_;q=0.8”)  
.doNotTrackHeader(“1”)  
.acceptLanguageHeader(“en-US,en;q=0.5”)  
.acceptEncodingHeader(“gzip, deflate”)  
.userAgentHeader(“Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Firefox/31.0”)

val scn = scenario(“BasicSimulation”)  
.exec(http(“request\_1”)  
.get("/"))  
.pause(5)

_**setUp(scn.inject(atOnceUsers(1))).protocols(httpConf)**_  
}

But if _**I want to inject 20 users with a rate of 1 users every 3 seconds and hold this load for 10 minutes and with the same scenario I want to add 30 users with a rate of 1 users every 3 seconds (therefore we have a total of 50 users) and hold this load for 10 minutes.**_

How can I write that simulation setup ?

Thanks a lot

Viet Minh