Stress test your backend with Gatling

Performance tests with
Gatling
Andrzej Ludwikowski

About me
➔aludwikowski.blogspot.com
➔github.com/aludwiko
➔@aludwikowski

Performance tests - why so hard?
Simulate production as close as possible:
● hardware
○ CPU, RAM, storage, ...
● software
○ OS, Virtualization, DBs, …
● load
● isolation

Necessary to have:
● infrastructure
● monitoring
● logging

● Your performance intuition is wrong!
1. collect the data (monitoring, logging, profiling)
2. find the bottleneck (based on data)
3. fix the bottleneck
4. collect the data and check the assumptions
5. go to 1.

Lies, damned lies, and statistics:
● arithmetic mean = 2.9
● median = 1
● standard deviation = 6 (only for normal distribution)

● Anscombe's quartet
http://bravenewgeek.com/tag/coordinated-omission/
Property Value
Mean of x 9
Sample variance of x 11
Mean of y 7.50
Sample variance of y 4.125
Correlation between x and y 0.816
Linear regression line y = 3 + 0.5x
Coefficient of determination of
the linear regression
0.67

Lies, damned lies, and statistics:
● arithmetic mean = 2.9
● median = 1
● standard deviation = 6 (only for normal distribution)
Use:
percentiles
50th = 1
70th = 1
90th = 2.9
95th = 11.45
99th = 18.29
Check percentiles implementation!

● Coordinated omission problem by Gil Tene

Coordinated omission problem
system.exit(0)

system.exit(0)
samples 31
50 th 1
70 th 1
90 th 1
95 th 1
99 th 12.89
99,9 th 28.30
99,99 th 29.82
avg 1.93

system.exit(0)
samples 10001
50 th 1
70 th 1
90 th 1
95 th 1
99 th 1
99,9 th 1.15
99,99 th 28.01
avg 1.03

system.exit(0)
samples 60
50 th 1
70 th 12.6
90 th 24.3
95 th 27.2
99 th 29.45
99,9 th 29.95
99,99 th 29.99
avg 8.25

total time 60 s
max 30 s
99th 1 s

total time 60 s
max 30 s
99th 1 s
time in % for max 50%

total time 60 s
max 30 s
99th 1 s
expected time in % for 99th 50% - 1% = 49%

total time 60 s
max 30 s
99th 1 s
expected time in % for 99th 50% - 1% = 49%
real time for 99th 60 s * 49% = 29.4 s

● Coordinated omission vs Gatling

● Tests…

Why Gatling?
● non-blocking, asynchronous stack (scala, akka, netty)
● scala !!!111oneoneone (maven, sbt support)
● DSL
● recorder
● math is good
● reports
● integration & performance tests

Gatling DSL
class BasicSimulation extends Simulation {
val httpConf = http
.baseURL("http://computer-database.gatling.io")
.acceptHeader("text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8")
.acceptEncodingHeader("gzip, deflate")
.acceptLanguageHeader("en-US,en;q=0.5")
.userAgentHeader("Mozilla/5.0 (Macintosh; X 10.8; rv:16.0) Gecko/20100101 Firefox/16.0")
val firstScenario = scenario("First Scenario Name")
.exec(http("Request name").get("/"))
.pause(7)
setUp(firstScenario.inject(atOnceUsers(1)).protocols(httpConf))
}

Gatling DSL
class FirstScenarioV2 extends MySimulation {
.exec(http("Go to root page").get("/"))
.pause(7 seconds)
}

Gatling DSL
import io.gatling.core.Predef._
import io.gatling.http.Predef._
class FirstScenarioV2 extends MySimulation {
.exec(http("Go to root page").get("/"))
.pause(7 seconds)
}

Gatling DSL
class ComplexScenario extends MySimulation {
val complexScenario = scenario("Complex demo scenario")
.exec(http("request_1").get("/")).pause(7)
.exec(http("request_2").get("/computers?f=macbook")).pause(2)
.exec(http("request_3").get("/computers/6")).pause(3)
.exec(http("request_4").get("/")).pause(2)
.exec(http("request_5").get("/computers?p=1")).pause(670 milliseconds)
.exec(http("request_6").get("/computers/new")).pause(1)
.exec(http("request_7")
.post("/computers")
.formParam("name", "MyComputer").formParam("introduced", "2012-05-30").formParam("company", "37"))
setUp(complexScenario.inject(atOnceUsers(1)).protocols(httpConf))
}

Gatling DSL
class ComplexScenarioV2 extends MySimulation {
val complexScenario = scenario("Complex demo scenario")
.exec(goToRootPage).pause(7)
.exec(searchFor("macbook")).pause(2)
.exec(positionAt(6)).pause(3)
.exec(goToRootPage).pause(2)
.exec(goToPage(1)).pause(670 milliseconds)
.exec(openNewComputerForm).pause(1)
.exec(addNewComputer)
}

Gatling DSL
class ComplexScenarioV3 extends MySimulation {
val search = exec(goToRootPage).pause(7)
.exec(searchFor("macbook")).pause(2)
.exec(positionAt(6)).pause(3)
val addComputer = exec(goToRootPage).pause(2)
.exec(goToPage(1)).pause(670 milliseconds)
.exec(openNewComputerForm).pause(1)
.exec(addNewComputer)
val complexScenario = scenario("Complex demo scenario").exec(search, addComputer)
}

Gatling DSL - checks
scenario("DSL demo")
.exec(http("go to page")
.get("/computers")
.check(status.is(200))
.check(status.in(200 to 210))

.exec(http("go to page")
.get("/computers")
.check(regex("computers")
.find(1)
.exists)
https://www.pinterest.com/pin/491666484294006138/

scenario("First Scenario Name")
.exec(http("Request name")
.get("/computers")
.check(jsonPath("$..foo.bar[2].baz").ofType[String].notExists)
.check(xpath("//input[@id='text1']/@value").is("test"))
.check(css("...").transform(_.split('|').toSeq).is(Seq("1", "2")))

.exec(http("Authorize")
.get("/auth")
.check(regex("token").find(1).exists
.saveAs("authorizationToken")))
.exec(http("Authorized resource")
.get("/authorized_resource?token=${authorizationToken}"))

Gatling DSL - looping
repeat(5, "i") {
exec(goToPage("${i}".toInt))
.pause(1)
}
● repeat
● foreach
● during
● asLongAs
● forever
https://blog.hubspot.com/blog/tabid/6307/bid/32019/Why-Every-Marketer-Needs-Closed-Loop-Reporting.aspx#sm.0005lrqj811waf3ntmn1cul3881gr

Gatling DSL - polling
exec(
polling
.every(10 seconds)
.exec(searchFor("thinkpad"))
)
http://www.firmus-solutions.com/terms-conditions.html

Gatling DSL - conditions
doIf(session => session("user").as[String].startsWith("admin")) {
exec(goToAdminPage)
}
● doIf
● doIfEquals
● doIfOrElse
● doSwitch
● doSwitchOrElse
● randomSwitch
https://en.wikipedia.org/wiki/Decision_tree

Gatling DSL - error management
exec(sendMoney)
.tryMax(10){
exec(checkIfMoneyReceived)
}
● tryMax
● exitBlockOnFail
● exitHereIfFailed
Alice Bob
Kafka

Gatling DSL - setup
setUp(myScenario
.inject(
nothingFor(4 seconds),
atOnceUsers(10),
rampUsers(10) over (5 seconds))
.protocols(httpConf))
.maxDuration(10 minutes)
● constantUsersPerSec
● rampUsersPerSec
● splitUsers
● heavisideUsers

Gatling DSL - setup
setUp(myScenario
.inject(atOnceUsers(10))
.assertions(
global.responseTime.max.lt(50),
global.failedRequests.percent.is(0)
)
http://englishthroughlaxas.blogspot.com/2015/07/531-24-expression-of-assertion-emphasis.html

Gatling DSL - setup
setUp(myScenario
.inject(atOnceUsers(10))
.throttle(
reachRps(100) in (30 second),
holdFor(1 minute),
jumpToRps(50),
holdFor(2 hours)
)

Gatling DSL - feeders
val companies = List("apple", "lenovo", "hp")
val feeder = Iterator.continually(
Map("company" -> companies(Random.nextInt(companies.size))))
val searching = scenario("Searching")
.feed(feeder)
.exec(searchFor("${company}"))
● RecordSeqFeederBuilder
● CSV
● JSON
● JDBC
● Sitemap
● Redis
● … http://favim.com/orig/201104/23/Favim.com-22725.jpg

Gatling DSL - resource inferring
val httpConf = http
.baseURL("http://computer-database.gatling.io")
.acceptHeader("...")
.acceptEncodingHeader("...")
.acceptLanguageHeader("...")
.inferHtmlResources()
.userAgentHeader("...")

Gatling - launching
● gatling:test
● gatling:testOnly x.y.z.GetUserSimulation

Gatling DSL - other goodies
● Custom validators
● HTTP
○ SSL
○ SSE (Server Sent Event)
○ basic cookies support
● WebSocket
● JMS
● Pluginable architecture:
○ cassandra plugin
○ kafka plugin
○ rabbitMQ
○ AMQP

Gatling DSL - logging/debugging
● logging ALL HTTP request and responses
<logger name="io.gatling.http.ahc" level="TRACE" />
<logger name="io.gatling.http.response" level="TRACE" />
● logging ONLY FAILED HTTP request and responses
<logger name="io.gatling.http.ahc" level="DEBUG" />
<logger name="io.gatling.http.response" level="DEBUG" />

Gatling DSL - reporting
================================================================================
---- Global Information --------------------------------------------------------
> request count 10 (OK=10 KO=0 )
> min response time 40 (OK=40 KO=- )
> max response time 177 (OK=177 KO=- )
> mean response time 55 (OK=55 KO=- )
> std deviation 41 (OK=41 KO=- )
> response time 50th percentile 42 (OK=42 KO=- )
> mean requests/sec 0.909 (OK=0.909 KO=- )
---- Response Time Distribution ------------------------------------------------
> t < 800 ms 10 (100%)
> 800 ms < t < 1200 ms 0 ( 0%)
> t > 1200 ms 0 ( 0%)
> failed 0 ( 0%)
================================================================================

Gatling DSL - distributed
IT system

Gatling DSL - distributed
● manually
● Gatling FrontLine
● Flood.io
IT system

Stress test your backend with Gatling

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