How to use feeder in gatling with 1 user and session, to make sequential HTTP requests

I am building a gatling feeder with 50 values in the sequence like this

var count = 0
val feeder = generateSequence {
    val takenCount = (count++).takeIf { it < 50 }

    if (takenCount != null) {
        mapOf(
            "requestParam" to "requestParamValue$count",
        )
    } else {
        null
    }
}.iterator()

and define the scenario

    val scn =
    scenario("Test scenario")
        .feed(feeder)
        .exec(
            http("Post request")
                .put("/someUrl")
                .header("Content-Type", "application/json")
                .body(
                    StringBody(
                        """
                        {
                            "requestParam": #{requestParam}
                        }""".trimIndent()
                    )
                )
        )
        .pause(1)

now, instead of using atOnceUsers(50) and making 50 concurrent HTTP requests like here

init {
    setUp(
        scn.injectOpen(
            atOnceUsers(50)
        ).protocols(httpProtocol)
    )
}

I'd like to make whatever number of requests in the feeder (50) sequentially with only 1 user

I believe Gatling does not allow feed to detect the end of feeder then stop the virtual user gracefully. So you'll have to specify the loop count.

You can launch only 1 user, then use repeat to loop through the feeder.

scenario("Test scenario")
    .repeat(50).on(
        feed(feeder)
        .exec(
            http("Post request")
                .put("/someUrl")
                .header("Content-Type", "application/json")
                .body(
                    StringBody(
                        """
                        {
                            "requestParam": #{requestParam}
                        }""".trimIndent()
                    )
                )
        )
        .pause(1)
    )
)