Gatling Kafka Plugin

Install

Maven:

Add to your pom.xml

<dependency>
    <groupId>io.github.amerousful</groupId>
    <artifactId>gatling-kafka</artifactId>
    <version>3.5</version>
</dependency>

SBT

Add to your build.sbt

libraryDependencies += "io.github.amerousful" % "gatling-kafka" % "3.5"

Import:

import io.github.amerousful.kafka.Predef._

---

Examples:

Protocol:

  val kafkaProtocol = kafka
  .broker(KafkaBroker("localhost", 9092))
  .acks("1")
  .producerIdenticalSerializer("org.apache.kafka.common.serialization.StringSerializer")
  .consumerIdenticalDeserializer("org.apache.kafka.common.serialization.StringDeserializer")
  .replyTimeout(10 seconds)
  .matchByKey()

Fire and forget:

  val kafkaFireAndForget = kafka("Kafka: fire and forget")
  .send
  .topic("input_topic")
  .payload(StringBody("#{payload}"))
  .key("#{key}")
  .headers(Map(
    "header_1" -> "#{h_value_1}",
    "header_2" -> "#{h_value_2}",
  ))

Request and reply:

  val kafkaRequestWithReply = kafka("Kafka: request with reply")
  .requestReply
  .topic("input_topic")
  .payload("""{ "m": "#{payload}" }""")
  .replyTopic("output_topic")
  .key("#{id} #{key}")
  .check(jsonPath("$.m").is("#{payload}_1"))

---

Scenario:

scenario("Kafka Scenario")
  .exec(kafkaFireAndForget)

Inject:

setUp(
  scn.inject(
    constantUsersPerSec(2) during(10 seconds)
  ).protocols(kafkaProtocol)
)

Java example

Kotlin example

---

How to make a request:

There are three types how to load Kafka:

1. Just send a request into a Topic without any wait, Fire-and-forget

kafka("Kafka: fire and forget")
  .send
  ...

2. Send a request into an input Topic, and then wait an outcome message from an output Topic

kafka("Kafka: request with reply")
  .requestReply
  ...
  .replyTopic("output_topic")

3. Only consume.

 kafka("Kafka: Only consume")
    .onlyConsume
    .readTopic("#{output_topic}")
    .payloadForTracking {
      "payload"
    }
    .keyForTracking("key")
    .startTime("#{currentTimeMillis()}")

Obviously, it doesn't send any message, but as it needs to match messages, there are methods similar as for request-reply: payloadForTracking, keyForTracking and header(s)ForTracking

Another aspect to consider is the potential usefulness of tracking when a message is triggered and determining the elapsed time for its entire processing chain. To facilitate this, the method startTime allows you to input a specific time value in milliseconds.

-- Send HTTP request
-- Write the start point into Session
-- Consume a message from Kafka

If startTime is not passed, it defaults to the current time.

---

In a case with request-reply you have to define in a protocol waiting time for the reply:

.replyTimeout(10 seconds)

Another thing that you have to provide it's how to match a message. There are several options:

1. matchByKey()
2. matchByValue()
3. Custom matcher:

object CustomMatcher extends KafkaMatcher {
  override def requestMatchId(msg: ProducerRecord[String, String]): String = ???

  override def responseMatchId(msg: ConsumerRecord[String, String]): String = ???
}

...

.messageMatcher(CustomMatcher)

Chain for build a request:

send -> 
            topic() -> 
                payload() -> 
                    key() / headers() 

requestReply -> 
            topic() -> 
                payload() -> 
                        replyTopic() -> 
                            key() / headers() / check() / protobufOutput()
                            
onlyConsume -> 
            readTopic() -> 
                payloadForTracking() -> 
                            keyForTracking() / headerForTracking() / check() / startTime() / protobufOutput()

Reply consumer name:

1. Static name: .replyConsumerName("gatling-test-consumer")
2. If you don't define a static name it will generate by pattern gatling-test-${java.util.UUID.randomUUID()}

Logs:

Add to your logback.xml:

<logger name="io.github.amerousful.kafka" level="ALL"/>

---

Protobuf

Starting from version 3.0, support for Protobuf payloads has been introduced. Please note that all examples provided assume the usage of Scala with Maven as the setup. This functionality works with classes generated through ScalaPB.

Instruction:

1. Create a .proto file.

src/
└── test/
    └── resources/
        └── protobuf/
            └── service.proto

service.proto

syntax = "proto3";

package proto;

message AuthLocal {
  string token = 1;
  int32 id = 2;
  string email = 3;
}

message Order {
  string name = 1;
}

2. Add to the pom.xml Protobuf class generator.
   Important! You have to define output for both Java and Scala.

...
<build>
    <testSourceDirectory>src/test/scala</testSourceDirectory>
    <plugins>
        <plugin>
            <groupId>com.github.os72</groupId>
            <artifactId>protoc-jar-maven-plugin</artifactId>
            <version>3.11.4</version>
            <executions>
                <execution>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>run</goal>
                    </goals>
                    <configuration>
                        <addProtoSources>all</addProtoSources>
                        <includeMavenTypes>transitive</includeMavenTypes>
                        <inputDirectories>
                            <include>src/test/</include>
                        </inputDirectories>
                        <outputTargets>

                            <outputTarget>
                                <type>java</type>
                                <addSources>test</addSources>
                                <outputDirectory>${project.basedir}/target/generated-sources/protobuf
                                </outputDirectory>
                                <pluginArtifact>com.thesamet.scalapb:protoc-gen-scala:0.11.15:sh:unix
                                </pluginArtifact>
                            </outputTarget>

                            <outputTarget>
                                <type>scalapb</type>
                                <addSources>test</addSources>
                                <outputDirectory>${project.basedir}/target/generated-sources/protobuf
                                </outputDirectory>
                                <outputOptions>java_conversions</outputOptions>
                                <pluginArtifact>com.thesamet.scalapb:protoc-gen-scala:0.11.15:sh:unix
                                </pluginArtifact>
                            </outputTarget>

                        </outputTargets>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
...

3. Run in a console mvn generate-sources.
4. Generated classes will be in the path /target/generated-sources/protobuf.
5. Import the generated class for use in requests and scenarios import proto.service.AuthLocal (it's Scala class and object)
6. Pass Scala case classes as payloads It implicitly converts Scala to Java.

.payload(
    // Scala case class with all fields
    AuthLocal("myToken", 123, "abc@xyz.com")
)
  
.payload { session =>
    val token = session("token").as[String]
    AuthLocal(token, 123, "abc@xyz.com")
}

7. Deserialization into Protobuf and working in the check with objects.

.protobufOutput(AuthLocal)
.check(
    protobufResponse((auth: AuthLocal) => auth.id) is 123
)

8. Protocol.

.consumerKeyDeserializer("org.apache.kafka.common.serialization.StringDeserializer")
  
.producerKeySerializer("org.apache.kafka.common.serialization.StringSerializer")
.producerValueSerializer("io.confluent.kafka.serializers.protobuf.KafkaProtobufSerializer")
  
.schemaUrl("http://localhost:8085")

As you see, there no needed to pass consumer Protobuf deserializer for value. Because it resolves by the protobufOutput method.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

License

MIT