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Creating Workflows

Workflows are a sequence of steps that define the logic and flow of a process. They are used to automate business processes, manage data, and coordinate tasks. The Workflow Engine provides a flexible and scalable platform for creating and executing workflows.

Workflows can be created using a code-first approach or a designer-first approach. The code-first approach involves writing workflows using a programming language, while the designer-first approach involves using a visual designer in the Workflow Studio to create workflows.

Please see the Creating Workflows Using the Workflow Studio guide for more information on the designer-first approach.

This guide details the technical, but more powerfull code-first approach to writing workflows. It covers the lifecycle methods, behind-the-scenes workings, and provides an example workflow to help you get started.

Workflow Lifecycle​

A workflow in the Workflow Engine goes through several stages during its lifecycle. The main stages are:

  1. Authorization: The workflow checks if it has the necessary permissions to proceed.
  2. Initiation: The workflow starts and processes the initial payload.
  3. Hibernate: The workflow pauses and waits for a specific event or message.
  4. Resume: The workflow resumes from the hibernated state.
  5. Terminate: The workflow completes its execution and performs cleanup.
  6. Recover: The workflow recovers from a failure or restart.

Diagram of the Workflow Lifecycle​

Creating a Workflow​

To create a new workflow, you need to define a class that extends the Workflow class. The new class should implement the necessary lifecycle methods to handle the workflow logic.

Example Workflow Class Definition​

import Workflow from '../../classes/Workflow.js';

export default class ExampleWorkflow extends Workflow {
  static workflowName = "ExampleWorkflow";
  static workflowVersion = "2.0";

  constructor(instanceId = null, workflowDeadlineInMinutes = 1440) {
    super(instanceId, workflowDeadlineInMinutes);
    this.name = ExampleWorkflow.workflowName;
    this.version = ExampleWorkflow.workflowVersion;
  }

  async OnAuthorize(payload) {
    console.log(`📝 Authorization in process...`);
    return true;
  }

  async OnInitiate(payload) {
    console.log(`👤 ExampleWorkflow \${this.instanceId} initiated`);
    await this.TestActivity(payload);
    return { instanceId: this.instanceId, message: "Workflow initiated successfully." };
  }

  async TestActivity(payload) {
    console.log(`👤 Running TestActivity with payload: \${JSON.stringify(payload)}`);
    await this.Wait(payload.correlationId, this.ResumeAndTerminate.bind(this), 5);
  }

  async OnHibernate() {
    console.log("👤 ******Going to Sleep*****");
  }

  async OnResume() {
    await super.OnResume();
    console.log("👤 ******Resumed...*****");
    await this.ResumeAndTerminate();
  }

  async ResumeAndTerminate(payload) {
    console.log("👤 After Resume:");
    console.log(`👤 Response received for workflow \${this.instanceId}`);
    await this.Terminate();
  }

  async OnRecover() {
    await super.OnResume();
    console.log("👤 ******Recovered...*****");
    await this.OnInitiate(); // Start over
  }

  async OnTerminate() {
    console.log(`👤 ExampleWorkflow \${this.instanceId} specific termination logic executed.`);
  }
}

Lifecycle Methods​

OnAuthorize​

The OnAuthorize method is called to authorize the workflow. It should return a boolean indicating whether the authorization was successful.

async OnAuthorize(payload) {
  console.log(`📝 Authorization in process...`);
  return true; // or false based on the logic
}

OnInitiate​

The OnInitiate method is called to initiate the workflow. It processes the initial payload and sets up the workflow state.

async OnInitiate(payload) {
  console.log(`👤 ExampleWorkflow \${this.instanceId} initiated`);
  await this.TestActivity(payload);
  return { instanceId: this.instanceId, message: "Workflow initiated successfully." };
}

OnHibernate​

The OnHibernate method is called when the workflow is hibernated.

async OnHibernate() {
  console.log("👤 ******Going to Sleep*****");
}

OnResume​

The OnResume method is called when the workflow is resumed.

async OnResume() {
  await super.OnResume();
  console.log("👤 ******Resumed...*****");
  await this.ResumeAndTerminate();
}

OnTerminate​

The OnTerminate method is called when the workflow is terminated.

async OnTerminate() {
  console.log(`👤 ExampleWorkflow \${this.instanceId} specific termination logic executed.`);
}

OnRecover​

The OnRecover method is called to recover the workflow after a failure or restart.

async OnRecover() {
  await super.OnResume();
  console.log("👤 ******Recovered...*****");
  await this.OnInitiate(); // Start over
}

Behind the Scenes​

Workflow Management​

The WorkflowManagement class is responsible for managing the lifecycle of workflow instances. It provides methods to add, retrieve, remove, and persist workflow instances.

Instance Map Store​

The InstanceMapStore class is a singleton that stores workflow instances in memory. It provides methods to add, retrieve, and remove instances.

Message Distribution​

The MessageDistributionService class handles the distribution of messages to workflow instances. It subscribes to various events and distributes messages accordingly.

Queue Management​

The QueueManager class manages a queue of messages that need to be processed. It ensures that messages are processed efficiently and handles retries.

Example Workflow​

Here's an example of how to create and run the ExampleWorkflow workflow:

import ExampleWorkflow from './workflows/ExampleWorkflow.mjs';

const payload = {
  alias: "agent123",
  requestId: "req-456",
  metadata: {
    customerName: "John Doe",
    customerEmail: "john.doe@example.com"
  },
  skipVoiceCheck: false
};

async function runWorkflow() {
  const workflow = new ExampleWorkflow();
  await workflow.OnAuthorize(payload);
  await workflow.OnInitiate(payload);
  await workflow.TestActivity(payload);
}

runWorkflow().catch(error => {
  console.error("Error running ExampleWorkflow:", error);
});

Conclusion​

This documentation provides a comprehensive guide on how to write a workflow using the Workflow Engine. It covers the lifecycle methods, behind-the-scenes workings, and provides an example workflow to help you get started. By following this guide, you can create robust and maintainable workflows for various use cases.

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