crafting the body for request does not work concurrently - scala

Question

I would like to send simultaneous requests through gatlings for some duration
below is the snippet of my code where I am crafting the requests.
JSON file contents function which is used for crafting the json. its been used in the main request
the TestDevice_dev.csv has list of devices till 30 after 30 I will reuse it.
TestDevice1
TestDevice2
TestDevice3
.
.
.
val dFeeder = csv("TestDevice_dev.csv").circular
val trip_dte_tunnel_1 = scenario("TripSimulation")
.feed(dFeeder)
.exec(session => {
val key = conf.getString("config.env.sign_key")
var bodyTrip = CannedRequests.jsonFileContents("${deviceID}")
//deviceId comes from the feeder
session.set("trip_sign", SignatureGeneration.getSignature(key, bodyTrip))
session.set("tripBody",bodyTrip)
})
.exec(http("trip")
.post(trip_url)
.headers(trip_Headers_withsign)
.body(StringBody("${tripBody}")).asJSON.check(status.is(201)))
.exec(flushSessionCookies)
the scenario is started as below
val scn_trip = scenario("trip simulation")
.repeat{1} {
exec(DataExchange.trip_dte_tunnel_1)
}
setUp(scn_trip.inject(constantUsersPerSec(5) during (5 seconds))) ```
it runs fine if there is 1 user for 5 seconds but not simulatenous users.
the json request which is crafted looks like the below
"events":[
{
"deviceDetailsDataModel":{
"deviceId":"<deviceID>"
},
"eventDateTime":"<timeStamp>",
"tripInfoDataModel":{
"ignitionStatus":"ON",
"ignitionONTime":"<onTimeStamp>"
}
},
{
"deviceDetailsDataModel":{
"deviceId":"<deviceID>"
},
"eventDateTime":"<timeStamp>",
"tripInfoDataModel":{
"ignitionStatus":"ON",
"ignitionONTime":"<onTimeStamp>"
}
},
{
"deviceDetailsDataModel":{
"deviceId":"<deviceID>"
},
"eventDateTime":"<timeStamp>",
"tripInfoDataModel":{
"ignitionOFFTime":"<onTimeStamp>",
"ignitionStatus":"OFF"
}
}
]
}`
`def jsonFileContents(deviceId: String): String= {
val fileName = "trip-data.json"
var stringBuilder=""
var timeStamp1:Long = ZonedDateTime.now(ZoneId.of("America/Chicago")).toInstant().toEpochMilli().toLong - 10000.toLong
for (line <- (Source fromFile fileName).getLines) {
if (line.contains("eventDateTime")) {
var lineReplace=line.replaceAll("<timeStamp>", timeStamp1.toString())
stringBuilder=stringBuilder+lineReplace
timeStamp1 = timeStamp1+1000.toLong
}
else if (line.contains("onTimeStamp")) {
var lineReplace1=line.replaceAll("<onTimeStamp>", timeStamp1.toString)
stringBuilder=stringBuilder+lineReplace1
}
else if (line.contains("deviceID")){
var lineReplace2=line.replace("<deviceID>", deviceId)
stringBuilder=stringBuilder+lineReplace2
}
else {
stringBuilder =stringBuilder+line
}
}
stringBuilder
}
`

Answer 1

Best guess: your feeder contains one single entry and you're using the default queue strategy. Either add more entries in your feeder file to match the number of users, or use a different strategy.
This really is explained in the documentation, including the tutorials. I recommend you take some time to read the documentation before rushing into the code, you'll save lots of time in the end.

Answer 2

You don't need to do your own parameter substitution of values in the json file - Gatling supports passing en ELFileBody as the body where you can have a json file with gatling EL expressions like ${deviceId}.