Using feeder to build query string

Gatling (Open-Source)
1

Hi everyone,

I want to hit a url with a query string built based on a feeder. It’s easier with an example:

ids.csv
id
1
2
3
4
5

http://localhost?ids=1,2,3

Each time I run the scenario, I’d like to have a different number of randomly picked IDs.
http://localhost?ids=2,5

http://localhost?ids=1,3,5

etc.

I’ve tried to do the following but it doesn’t work.

val scn = scenario(“My scenario”)
.feed(csv(“ids.csv”).random)
.exec(
http(“request_1”)
.get(session => “?ids=” + buildIdList)
.check(status.is(200)))

// Will create a string like “{id}{id}{id}” with a random number of {id}
def buildIdList = (0 to new Random().nextInt(10) + 1).map(n => “${id}”).toList.mkString(",")

I was hoping Gatling will replace each {id} in the built query string with a value from the feeder but id doesn’t.

I’d appreciate if you have any ideas. Thanks,

Ariel

2

Hi,

Fist, you won’t be able to directly use the whole Feeder API, but you can re-use the Feeder utilities.

Then, I might be wrong, but it’s more likely that you actually need unique randomly picked ids.
If so, a simple approach would be to inject into a Set, but if your possible values list is not big enough, collisions would be high, so your distribution would change and you’d need a more complex approach.

With Gatling 2:

val data: Array[Map[String, String]] = csv(“ids.csv”).data // get the underlying array

val feedIds = (session: Session) => {
val random = ThreadLocalRandom.current
val ids = (0 to random.nextInt(10 + 1).map(n = data(n)(“id”).toSet.mkString(",")
session.set(“ids”, ids)
}

exec(feedIds)
.exec(http(“request_1”).get("?ids=${ids}").check(status.is(200)))

}

Get it?

Cheers,

Stéphane

3

Hi Stéphane,

Thanks for the quick response. I’ve been trying to make it work but I haven’t been successful.

exec seems to take a Session => Validation[Session] as a parameter, so I’ve changed the last line of feedIds to be

new Success(session.set(“ids”, ids))

I set the log level to DEBUG and when I try to run the simulation, apparently no requests are being made. I just read

14:53:46.947 [DEBUG] i.g.c.r.Runner - Finished Launching scenarios executions
14:53:46.949 [INFO ] i.g.c.a.UserStart - Start user #0
14:53:46.949 [INFO ] i.g.c.a.UserEnd - End user #0
14:53:48.076 [INFO ] i.g.c.a.UserStart - Start user #1
14:53:48.076 [INFO ] i.g.c.a.UserEnd - End user #1

Does it ring any bell? Thanks a lot,

Ariel

4

Hi Stéphane,

Thanks for the quick response. I've been trying to make it work but I
haven't been successful.

exec seems to take a Session => Validation[Session] as a parameter, so
I've changed the last line of feedIds to be

new Success(session.set("ids", ids))

There's an implicit conversion in core.Predef that turns T into
Validation[T], so you should have been fine. Do you import core.Predef?

I set the log level to DEBUG and when I try to run the simulation,
apparently no requests are being made. I just read

14:53:46.947 [DEBUG] i.g.c.r.Runner - Finished Launching scenarios
executions
14:53:46.949 [INFO ] i.g.c.a.UserStart - Start user #0
14:53:46.949 [INFO ] i.g.c.a.UserEnd - End user #0
14:53:48.076 [INFO ] i.g.c.a.UserStart - Start user #1
14:53:48.076 [INFO ] i.g.c.a.UserEnd - End user #1

Does it ring any bell? Thanks a lot,

Usually happens when once forgets a dot, so that execs are not properly
chained.

Could you share a gist, please?

5

https://gist.github.com/arikogan/7084579

6

Regarding the implicit not happening, my fault (directly coded in gmail): you need to declare expected type to make implicit conversion happen:

import io.gatling.core.session.Expression

val feedIds: Expression[Session] = …

Otherwise, the “cool” way is:

import io.gatling.core.validation._

session.set(“ids”, ids).success

Regarding the “no requests”, as I expected, there’s a missing dot line 25 in your gist:

https://gist.github.com/arikogan/7084579#file-retrieveids-scala-L25

7

That’s great, that did work Stéphane. Thank you.

I’m still confused about when to use the methods imported by import bootstrap._ and when not to. That was the problem in this thread. If you can shed some light on that, that would be helpful.

8

bootstrap is actually an object. importing bootstrap._ puts all its methods in scope, like exec.

It will be removed in M4.