wrk with lua script - generating multiple POST requests with different body

Question

I wrote some lua script for wrk to generate multiple POST requests. My problem is that my script is working only for the first request. All further generated requests are exactly the same as the first one. I would like that user variable will be new generated for each POST request:

lowerCase = "abcdefghijklmnopqrstuvwxyz" 
characterSet = lowerCase
   
keyLength = 13
user = ""    
math.randomseed(os.time())
for i = 1, keyLength do
rand = math.random(#characterSet)
user = user .. string.sub(characterSet, rand, rand )
end


wrk.path  = "/somepath"
wrk.method = "POST"
wrk.body   = [[{"username":"]].. user .. [[,"password":"somepassword"}]]
wrk.headers["Content-Type"] = "application/json"

this code only creates a single request with some random user name. if you have issues creating multiple requests you should show us how you do that — Piglet, Jul 21 '21 at 08:32
Hi, I am running it from the command line using: ```wrk -t1 -c3 -d10s https://endpoint -s filenamewithscript.lua``` — panigale, Jul 21 '21 at 08:34
wrk executes script single time and uses the identical request for all requests. Luckily, script has overridable functions, particulary `request`, which gets called for every request. Luckily someone provided answer how to use it :) — Janis Veinbergs, Feb 23 '22 at 15:35

score 3 · Answer 1 · answered Jul 30 '21 at 21:06

Try something like this. It should execute request3 ~50% of the time, and the other two ~25% of the time. Cheers!

names = { "Maverick", "Goose", "Viper", "Iceman", "Merlin", "Sundown", "Cougar", "Hollywood", "Wolfman", "Jester" }

request1 = function()
    headers = {}
    headers["Content-Type"] = "application/json"
    body = '{"name": ' .. names[math.random(#names)] .. '}'
    return wrk.format("POST", "/test1", headers, body)
end

request2 = function()
    headers = {}
    headers["Content-Type"] = "application/json"
    body = '{"name": ' .. names[math.random(#names)] .. '}'
    return wrk.format("POST", "/test2", headers, body)
end

request3 = function()
    headers = {}
    headers["Content-Type"] = "application/json"
    body = '{"name": ' .. names[math.random(#names)] .. '}'
    return wrk.format("GET", "/test3", headers, body)
end

requests = {}
requests[0] = request1
requests[1] = request2
requests[2] = request3
requests[3] = request3

request = function()
    return requests[math.random(0, 3)]()
end

response = function(status, headers, body)
    if status ~= 200 then
        io.write("------------------------------\n")
        io.write("Response with status: ".. status .."\n")
        io.write("------------------------------\n")
        io.write("[response] Body:\n")
        io.write(body .. "\n")
    end
end

Thanks! Documentation to more goodies/overridable functions: https://github.com/wg/wrk/blob/master/SCRIPTING — Janis Veinbergs, Feb 23 '22 at 15:33

Piglet · Answer 2 · 2021-07-21T10:56:46.963

0

I'm not familiar with wrk.

I guess you're running that code multiple times within a second. As os.time has second accuracy you'll have the same randomseed and hence the same user name within that second.

From looking into the scripting examples I'd say the script is only evaluated once or maybe once per thread. Those examples implement functions that will be called by wrk. It wouldn't make sense to define those functions for every request.

Add a print to your script to make sure.

Here is an example that counts requests. You probably can put your code into that function

function request()
   requests = requests + 1
   return wrk.request()
end

edited Jul 21 '21 at 10:56

answered Jul 21 '21 at 08:39

Piglet

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Within that second - yes, but If I run a test for 10seconds I should be able to see different values generated, but it shows me all the time only the first one. Lets wait maybe someone with WRK experience will be able to help. Thanks – panigale Jul 21 '21 at 10:35
see edit. I suggest you read through the scripting examples again. – Piglet Jul 21 '21 at 10:51

wrk with lua script - generating multiple POST requests with different body

2 Answers2