Gatling2 Failing to use user session properly

I hope someone can point me into the right direction! I try to run one scenario which has several steps that have to be executed in order and each with the same user session to work properly. The below code works fine with one user but fails if I use 2 or more users... What am I doing wrong?

 val headers = Map(
Constants.TENANT_HEADER -> tenant
)
val httpConf = http
.baseURL(baseUrl)
.headers(headers)

val scen = scenario("Default Order Process Perf Test")
.exec(OAuth.getOAuthToken(clientId))
.exec(session => OAuth.createAuthHHeader(session, clientId))
.exec(RegisterCustomer.registerCustomer(customerMail, customerPassword, 
  tenant))
.exec(SSO.doLogin(clientId, customerMail, customerPassword, tenant))
.exec(session => OAuth.upDateAuthToken(session, clientId))
.exec(session => 

UpdateCustomerBillingAddr.prepareBillingAddrRequestBody(session))
.exec(UpdateCustomerBillingAddr.updateCustomerBillingAddr(tenant))
.exec(RegisterSepa.startRegisterProcess(tenant))
.exec(session => RegisterSepa.prepareRegisterRequestBody(session))
.exec(RegisterSepa.doRegisterSepa(tenant))

setUp(
 scen
  .inject(atOnceUsers(2))
  .protocols(httpConf))

object OAuth {

private val OBJECT_MAPPER = new ObjectMapper()

def getOAuthToken(clientId: String) = {
val authCode = PropertyUtil.getAuthCode
val encryptedAuthCode = new 

Crypto().rsaServerKeyEncrypt(authCode)

http("oauthTokenRequest")
  .post("/oauth/token")
  .formParam("refresh_token", "")
  .formParam("code", encryptedAuthCode)
  .formParam("grant_type", "authorization_code")
  .formParam("client_id", clientId)
  .check(jsonPath("$").saveAs("oauthToken"))
  .check(status.is(200))
}

def createAuthHHeader(session: Session, clientId: String) = {
val tokenString = session.get("oauthToken").as[String]
val tokenDto = OBJECT_MAPPER.readValue(tokenString, 
classOf[TokenDto])
val session2 = session.set(Constants.TOKEN_DTO_KEY, tokenDto)

val authHeader = AuthCommons.createAuthHeader(tokenDto, 
clientId, new util.HashMap[String, String]())
session2.set(Constants.AUTH_HEADER_KEY, authHeader)
}

def upDateAuthToken(session: Session, clientId: String) = {
val ssoToken = session.get(Constants.SSO_TOKEN_KEY).as[String]
val oAuthDto = session.get(Constants.TOKEN_DTO_KEY).as[TokenDto]

val params = new util.HashMap[String, String]
params.put("sso_token", ssoToken)

val updatedAuthHeader = AuthCommons.createAuthHeader(oAuthDto, 
clientId, params)

session.set(Constants.AUTH_HEADER_KEY, updatedAuthHeader)
}
}

  def createAuthHHeader(session: Session, clientId: String) = {
val tokenString = session.get("oauthToken").as[String]
val tokenDto = OBJECT_MAPPER.readValue(tokenString, 
classOf[TokenDto])
val session2 = session.set(Constants.TOKEN_DTO_KEY, tokenDto)

val authHeader = AuthCommons.createAuthHeader(tokenDto, 
clientId, new util.HashMap[String, String]())
session2.set(Constants.AUTH_HEADER_KEY, authHeader)
}

So I did add the two methods that dont work along as expected. In the first part I try to fetch a token and store in the session via check(jsonPath("$").saveAs("oauthToken")) and in the second call I try to read that token with val tokenString = session.get("oauthToken").as[String] which fails with the exception saying that there is no entry for that key in the session...

Solution

I've copied it and removed/mocked any missing code references, switched to one of my apps auth url and it seems to work - at least 2 firsts steps.

One thing that seems weird is jsonPath("$").saveAs("oauthToken") which saves whole json (not single field) as attribute, is it really what you want to do? And are you sure that getOAuthToken is working properly?

You said that it works for 1 user but fails for 2. Aren't there any more errors? For debug I suggest changing logging level to TRACE or add exec(session => {println(session); session}) before second step to verify if token is properly saved to session. I think that something is wrong with authorization request (or building that request) and somehow it fails or throws some exception. I would comment out all steps except 1st and focus on checking if that first request is properly executed and if it adds proper attribute to session.