Hello World Application

This guide will walk you through building a "Hello World" workflow from scratch, covering these steps:

Creating a project
Writing tasks
Writing a workflow
Deploying workers
Starting a workflow

Our HelloWorkflow workflow will take a name string as input and return "Hello $name!", utilizing two tasks run on distributed workers:

A sayHello task that inputs a name string and outputs "Hello $name"
An addEnthusiasm task that inputs a str string and outputs "$str!"

Prerequisites

Before we begin, ensure you have installed the following dependencies:

Gradle
An Apache Pulsar cluster (installation guide)
A Redis (installation guide) or MySQL database for storing workflow states.

You can either run Redis and Pulsar on their own, or with Docker, you can set up the environment using the provided docker-compose.yml file:

services:
  # Pulsar
  pulsar-standalone:
    image: apachepulsar/pulsar:3.0.7
    environment:
      - BOOKIE_MEM=" -Xms512m -Xmx512m -XX:MaxDirectMemorySize=1g"
    command: >
      /bin/bash -c "bin/apply-config-from-env.py conf/standalone.conf && bin/pulsar standalone"
    volumes:
      - "pulsardata:/pulsar/data"
      - "pulsarconf:/pulsar/conf"
    ports:
      - "6650:6650"
      - "8080:8080"
      - "8081:8081"

  # Redis storage for state persistence
  redis:
    image: redis:6.0-alpine
    ports:
      - "6379:6379"
    volumes:
      - "redisdata:/data"

volumes:
  pulsardata:
  pulsarconf:
  redisdata:

Create project

Start by creating a new project:

mkdir hello-world && cd hello-world && gradle init

Configure this project by selecting the following settings (you may see slightly different prompts depending on your version of gradle):

Ensure that the version of Java you select matches what you have installed.

Select type of project to generate:
  1: basic
  2: application
  3: library
  4: Gradle plugin
Enter selection (default: basic) [1..4] 2

Select implementation language:
  1: C++
  2: Groovy
  3: Java
  4: Kotlin
  5: Swift
Enter selection (default: Java) [1..5] 3

Split functionality across multiple subprojects?:
  1: no - only one application project
  2: yes - application and library projects
Enter selection (default: no - only one application project) [1..2] 1

Select build script DSL:
  1: Groovy
  2: Kotlin
Enter selection (default: Kotlin) [1..2] 1

Project name (default: hello-world):
Source package (default: hello.world):

Select type of project to generate:
  1: basic
  2: application
  3: library
  4: Gradle plugin
Enter selection (default: basic) [1..4] 2

Select implementation language:
  1: C++
  2: Groovy
  3: Java
  4: Kotlin
  5: Swift
Enter selection (default: Java) [1..5] 4

Split functionality across multiple subprojects?:
  1: no - only one application project
  2: yes - application and library projects
Enter selection (default: no - only one application project) [1..2] 1

Select build script DSL:
  1: Groovy
  2: Kotlin
Enter selection (default: Kotlin) [1..2] 2

Select test framework:
  1: JUnit 4
  2: TestNG
  3: Spock
  4: JUnit Jupiter
Enter selection (default: JUnit 4) [1..4] 1

Project name (default: hello-world):
Source package (default: hello.world):

In our Gradle build file, we'll include:

The Maven repository
The required dependencies
A directive to compile using Java 17"

plugins {
    id 'application'
}

application {
    // Define the main class for the application.
    mainClassName = 'hello.world.App'
}

repositories {
    mavenCentral()
}

dependencies {
    // infinitic client
    implementation "io.infinitic:infinitic-client:0.16.1"
    // infinitic worker
    implementation "io.infinitic:infinitic-worker:0.16.1"
}

java {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

plugins {
    id("org.jetbrains.kotlin.jvm") version "2.0.0"

    application
}

repositories {
    mavenCentral()
}

dependencies {
    // infinitic client
    implementation("io.infinitic:infinitic-client:0.16.1")
    // infinitic worker
    implementation("io.infinitic:infinitic-worker:0.16.1")
}

tasks.withType<org.jetbrains.kotlin.gradle.services.KotlinCompile> {
    kotlinOptions.jvmTarget = JavaVersion.VERSION_17.toString()
}


application {
    // Define the main class for the application.
    mainClass.set("hello.world.AppKt")
}

Once you've updated your gradle build file, install the dependencies by running:

./gradlew install

Writing services

Next, create a services directory:

mkdir -p app/src/main/java/hello/world/services

Within this directory, define the `HelloServiceservice in its own file:

package hello.world.services;

import io.infinitic.annotations.Name;

@Name(name = "HelloService")
public interface HelloService {

    String sayHello(String name);

    String addEnthusiasm(String str);
}

package hello.world.services

import io.infinitic.annotations.Name

@Name("HelloService")
interface HelloService {
    fun sayHello(name: String): String

    fun addEnthusiasm(str: String): String
}

Within the same services directory, next define the HelloServiceImpl file, which will contain our tasks:

package hello.world.services;

public class HelloServiceImpl implements HelloService {
    @Override
    public String sayHello(String name) {
        return "Hello " + ((name == null) ? "World" : name);
    }

    @Override
    public String addEnthusiasm(String str) {
        return str + "!";
    }
}

package hello.world.services

class HelloServiceImpl : HelloService {
    override fun sayHello(name: String) = "Hello $name"

    override fun addEnthusiasm(str: String) = "$str!"
}

Writing workflow

Set up a workflows directory:

mkdir -p app/src/main/java/hello/world/workflows

Within it, add the HelloWorkflow interface:

package hello.world.workflows;

import io.infinitic.annotations.Name;

@Name(name = "HelloWorkflow")
public interface HelloWorkflow {
    String greet(String name);
}

package hello.world.workflows

import io.infinitic.annotations.Name

@Name("HelloWorkflow")
interface HelloWorkflow {
    fun greet(name: String): String
}

And its HelloWorkflowImpl implementation:

This implementation must extend io.infinitic.workflows.Workflow

package hello.world.workflows;

import hello.world.services.HelloService;
import io.infinitic.workflows.Workflow;

public class HelloWorkflowImpl extends Workflow implements HelloWorkflow {
    // create a stub for the HelloService
    private final HelloService helloService = newService(HelloService.class);

    @Override
    public String greet(String name) {
        // synchronous call of HelloService::sayHello
        String str = helloService.sayHello(name);

        // synchronous call of HelloService::addEnthusiasm
        String greeting =  helloService.addEnthusiasm(str);

        // inline task to display the result
        inlineVoid(() -> System.out.println(greeting));

        return greeting;
    }
}

package hello.world.workflows

import hello.world.services.HelloService
import io.infinitic.workflows.Workflow

class HelloWorkflowImpl: Workflow(), HelloWorkflow {
    // create a stub for the HelloService
    private val helloService = newService(HelloService::class.java)

    override fun greet(name: String): String {
        // synchronous call of HelloService::sayHello
        val str = helloService.sayHello(name)

        // synchronous call of HelloService::addEnthusiasm
        val greeting =  helloService.addEnthusiasm(str)

        // inline task to display the result
        inline { println(greeting) }

        return  greeting
    }
}

Note: the newService function creates a stub from the HelloService interface.

Syntax-wise, this stub functions like an implementation of HelloService. However, instead of executing a method directly, it sends a message to carry out the execution. This is why running a workflow without deploying any workers will result in no action being taken.

Pulsar configuration

Configure Pulsar in the app/infinitic.yml file:

transport:
  pulsar:
    brokerServiceUrl: pulsar://localhost:6650/
    webServiceUrl: http://localhost:8080
    tenant: infinitic
    namespace: dev

Deploying workers

Set up services and workflows, and update values for Redis and Pulsar connections as necessary:

transport:
  pulsar:
    brokerServiceUrl: pulsar://localhost:6650/
    webServiceUrl: http://localhost:8080
    tenant: infinitic
    namespace: dev

storage:
  redis:
    host: localhost
    port: 6379
    user:
    password:
    database: 0

services:
  - name: HelloService
    executor:
      class: hello.world.services.HelloServiceImpl
      concurrency: 10

workflows:
  - name: HelloWorkflow
    executor:
      class: hello.world.workflows.HelloWorkflowImpl
      concurrency: 10
    stateEngine:
      concurrency: 10
    tagEngine:
      concurrency: 10

Replace the App file with:

package hello.world;

import io.infinitic.worker.InfiniticWorker;

public class App {
    public static void main(String[] args) {
        try(InfiniticWorker worker = InfiniticWorker.fromConfigFile("infinitic.yml")) {
            worker.start();
        }
    }
}

package hello.world

import io.infinitic.worker.InfiniticWorker

fun main(args: Array<String>) {
    InfiniticWorker.fromConfigFile("infinitic.yml").use { worker ->
        worker.start()
    }
}

Our app is ready to run as a worker:

./gradlew run

We have a working worker listening Pulsar and waiting for instructions:

> Task :run
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

The SLF4J output messages appear because our app doesn't have a logger set up yet. To eliminate these messages, we can add a logger of our choice, such as Simple Logger, as a dependency in our Gradle build file.

When making code changes, it's necessary to restart the workers to ensure they incorporate these updates.

Start a workflow

Use a config file with pulsar configuration to instantiate an InfiniticClient. Use this client to create a workflow stub and dispatch the workflow.

Here, we already have the infinitic.yml file that we can reuse:

package hello.world;

import hello.world.workflows.HelloWorkflow;
import io.infinitic.client.Deferred;
import io.infinitic.client.InfiniticClient;

public class Client {
    public static void main(String[] args) {
        String name = args.length > 0 ? args[0] : "World";

        try(InfiniticClient client = InfiniticClient.fromConfigFile("infinitic.yml")) {
            // create a stub from HelloWorkflow interface
            HelloWorkflow helloWorld = client.newWorkflow(HelloWorkflow.class);

            // asynchronous dispatch of a workflow
            Deferred<String> deferred = client.dispatch(w::greet, name);

            // let's see what happens
            System.out.println("workflow " + HelloWorkflow.class.getName() + " " + deferred.getId() + " dispatched!");
        }
    }
}

package hello.world

import hello.world.workflows.HelloWorkflow
import io.infinitic.client.Deferred
import io.infinitic.client.InfiniticClient

fun main(args: Array<String>) {
    val name = args.firstOrNull() ?: "World"

    InfiniticClient.fromConfigFile("infinitic.yml").use { client ->
        // create a stub from HelloWorkflow interface
        val helloWorld = client.newWorkflow(HelloWorkflow::class.java)

        // dispatch workflow
        val deferred : Deferred<String> = client.dispatch(w::greet, name)

        // let's see what happens
        println("workflow ${HelloWorkflow::class} ${deferred.id} dispatched!")
    }
}

We can run this directly from our IDE (remembering to possibly adjust the working directory in the Run configuration), or we can add a startWorkflow Gradle task to our build file:

...
tasks.register('startWorkflow', JavaExec) {
    group = "infinitic"
    mainClass = "hello.world.Client"
    classpath = sourceSets.main.runtimeClasspath
}

...
task<JavaExec>("startWorkflow") {
    group = "infinitic"
    classpath = sourceSets["main"].runtimeClasspath
    mainClass.set("hello.world.ClientKt")
}

and run it from the command line:

./gradlew startWorkflow --args Infinitic

Where the app/worker is running, we should see:

Hello Infinitic!

Congrats! You have run your first Infinitic workflows.

Debugging

Check-list

In case of issues, check:

If Pulsar and Redis are running
Correctness of infinitic.yml file that
- should expose correct values to access Pulsar and Redis
- should have name and class that match interface names and implementation full names respectively of our task and workflows
If at least one worker is running

Keep in mind that workers will continue running even if an exception occurs in our tasks or workflows. To observe these exceptions, you need to set up a logger and then review the log file for any errors.

Simple logger

To use SimpleLogger as logger in this app, just add the dependency in our Gradle build file:

dependencies {
    ...
    implementation "org.slf4j:slf4j-simple:2.0.3"
    ...
}

dependencies {
    ...
    implementation("org.slf4j:slf4j-simple:2.0.3")
    ...
}

and this simplelogger.properties example file in our resources directory:

# SLF4J's SimpleLogger configuration file
# Simple implementation of Logger that sends all enabled log messages, for all defined loggers, to System.err.

# Uncomment this line to use a log file
#org.slf4j.simpleLogger.logFile=infinitic.log

# Default logging detail level for all instances of SimpleLogger.
# Must be one of ("trace", "debug", "info", "warn", or "error").
# If not specified, defaults to "info".
org.slf4j.simpleLogger.defaultLogLevel=warn

# Set to true if you want the current date and time to be included in output messages.
# Default is false, and will output the number of milliseconds elapsed since startup.
org.slf4j.simpleLogger.showDateTime=true

# Set to true if you want to output the current thread name.
# Defaults to true.
org.slf4j.simpleLogger.showThreadName=false


# Set to true if you want the last component of the name to be included in output messages.
# Defaults to false.
org.slf4j.simpleLogger.showShortLogName=true

Working repository

If we fail to chase a bug, we still can copy this working repository and look for the differences:

git clone https://github.com/infiniticio/infinitic-example-java-hello-world

git clone https://github.com/infiniticio/infinitic-example-kotlin-hello-world