WorkIt

✨Extensible worker for Node.js that works with both Zeebe and Camunda BPM platforms powered by TypeScript ✨

Motivation

We needed a framework to help us quickly build workers used to execute tasks. Zeebe provides a good fit with our stack. Until this is production ready, we are keeping the Camunda Bpm. Indeed, Zeebe is in developper preview. In order to make the transition smoother, we use this package. We can experiment and choose the Camunda platform we want without rewritting our business logic.

This package can be useful because:

• At this moment, Zeebe doesn't provide all BPMN components. Zeebe is new and some unexpected bugs can appear during development so we can easily revert back to the the former platform if an issue was to rise.
• Instead of depending directly from a Camunda client, this project provides an abstraction layer. This way it’s easier to change the client or to make your own.
• You want to have a worker standardization.
• Uniformisation. Indeed, you can use both platforms depending project needs.
• Added features like automated tracing.
• This package enforce feature parity between Zeebe and Camunda BPM through the client libraries. Some features exposed to the Camunda BPM platform are not presents in this package because we couldn't provide them if we switch to Zeebe. This limitation is to guide developers to prepare migration.

Quickstart

Get started in 2 minutes.

Documentation

• .docs contains written documentation
• Comprehensive API documentation is available online and in the docs subdirectory

Installing

npm i workit-camunda

or using the generator below

Yo!

This generator will help you during your development with this library. It provides handy tools.

npm i -g workit-cli

Install a fresh new project

workit init

Generate tasks from your existing BPMN

workit create task --file /your/path.bpmn

Generate new task

workit create task

How to use

Switching between Zeebe and the bpmn platform is easy as specifying a TAG to the IoC.

Run worker

const worker = IoC.get<Worker>(CORE_IDENTIFIER.worker, TAG.camundaBpm); // or TAG.zeebe

worker.start();
worker.run();

Deploy a workflow

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
const fullpath = `${process.cwd()}/sample/BPMN_DEMO.bpmn`;
await manager.deployWorkflow(fullpath);

Get workflows

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.getWorkflows()

Get a workflow

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.getWorkflow({ bpmnProcessId: "DEMO" });

Update variables

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.updateVariables({ 
    processInstanceId: "5c50c48e-4691-11e9-8b8f-0242ac110002",
    variables: { amount: 1000 }
});

Publish message

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.publishMessage({
    correlation: {},
    name: "catching",
    variables: { amount: 100 },
    timeToLive: undefined, // only supported for Zeebe
    messageId: "5c50c48e-4691-11e9-8b8f-0242ac110002"
});

Create workflow instance

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.createWorkflowInstance({
    bpmnProcessId: "MY_BPMN_KEY",
    variables: {
        hello: "world"
    }
});

Cancel workflow instance

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.cancelWorkflowInstance("4651614f-4b3c-11e9-b5b3-ee5801424400");

Resolve incident

const manager = IoC.get<IWorkflowClient>(CORE_IDENTIFIER.client_manager, TAG.camundaBpm); // or TAG.zeebe
await manager.resolveIncident("c84fce6c-518e-11e9-bd78-0242ac110003");

Define tasks (your bpmn activities)

You can define many tasks to one worker. It will handle all messages and will route to the right tasks.

export class HelloWorldTask extends TaskBase<IMessage> {
  // You can type message like IMessage<TBody, TProps> default any
  public execute(message: IMessage): Promise<IMessage> {
      const { properties } = message;
      console.log(`Executing task: ${properties.activityId}`);
      console.log(`${properties.bpmnProcessId}::${properties.processInstanceId} Servus!`);
      // put your business logic here
      return Promise.resolve(message);
  }
}


enum LOCAL_IDENTIFIER {
    // sample_activity must match the activityId in your bpmn
    sample_activity= 'sample_activity'
}

// Register your task
IoC.bindTo(HelloWorldTask, LOCAL_IDENTIFIER.sample_activity);

You can even make complex binding like

IoC.bindTask(HelloWorldTaskV2, LOCAL_IDENTIFIER.activity1, { bpmnProcessId: BPMN_PROCESS_ID, version: 2 });

See documentation

If you have installed workit-cli, you can do workit create task and everything will be done for you.

Worker life cycle and events

const worker = IoC.get<Worker>(CORE_IDENTIFIER.worker, TAG.zeebe); // or TAG.camundaBpm

worker.once('starting', () => {
    // slack notification 
});

worker.once('stopping', () => {
    // close connections
});

worker.once('stopped', () => {
    // slack notification
});

const handler = worker.getProcessHandler();

handler.on('message', (msg: IMessage) => {
    // log/audit
});

handler.on('message-handled', (err: Error, msg: IMessage) => {
    if (err) {
        // something wrong
    } else {
        // everything is fine
    }
});

worker.start();
worker.run(); // Promise
worker.stop(); // Promise

Interceptors

const workerConfig = {
  interceptors: [
    async (message: IMessage): Promise<IMessage> => {
      // do something before we execute task.
      return message;
    }
  ]
};

IoC.bindToObject(workerConfig, CORE_IDENTIFIER.worker_config);

Open-telemetry

By default, we bound a NoopTracer but you can provide your own and it must extend Tracer class.We strongly recommand to use this kind of pattern in your task: Domain Probe pattern. But here an example:

// Simply bind your custom tracer object like this
IoC.bindToObject(tracer, CORE_IDENTIFIER.tracer);

export class HelloWorldTask extends TaskBase<IMessage> {
  private readonly _tracer: TracerBase;
    
  constructor(tracer: TracerBase) {
        this._tracer = tracer
  }

  public async execute(message: IMessage): Promise<IMessage> {
      const { properties } = message;
      
      console.log(`Executing task: ${properties.activityId}`);
      console.log(`${properties.bpmnProcessId}::${properties.processInstanceId} Servus!`);
      message.body.test = true;
      // This call will be traced automatically
      const response = await axios.get('https://jsonplaceholder.typicode.com/todos/1');
      
      // you can also create a custom trace like this :
      const span = this._tracer.startChildSpan({ name: 'customSpan', kind: SpanKind.CLIENT });
      
      console.log();
      console.log('data:');
      console.log(response.data);
      // put your business logic here

      // finish the span scope
      span.end();
      
      return Promise.resolve(message);
  }
}

You can look to sample folder where we provide an example (parallel.ts) using Jaeger.

See get started section with OpenTelemetry

Define your config for each platform

const configBase: ICamundaConfig = {
    workerId: 'demo',
    baseUrl: `__undefined__`,
    topicName: 'topic_demo'
};

// For Camunda BPM platform
const bpmnPlatformClientConfig = { ...configBase, baseUrl: 'http://localhost:8080/engine-rest',  maxTasks: 32, autoPoll: false, use: [] };

IoC.bindToObject(bpmnPlatformClientConfig, CORE_IDENTIFIER.camunda_external_config);

// For Zeebe platform
const zeebeClientConfig = { ...configBase, { baseUrl: 'localhost:2650', timeout: 2000 };

// Zeebe exporter (Elasticsearch instance)
const zeebeElasticExporterConfig = {
    url: `http://localhost:9200`,
};

IoC.bindToObject(zeebeClientConfig, CORE_IDENTIFIER.zeebe_external_config);
IoC.bindToObject(zeebeElasticExporterConfig, CORE_IDENTIFIER.zeebe_elastic_exporter_config)

See documentation

Define your strategies in case of failure or success

By default, we define simple strategy for sucess or failure. We strongly recommend you to provide yours as your app trigger specific exceptions. Strategies are automatically handled. If an exeption is bubble up from the task, failure strategy is raised, otherwise it's success.

TODO: PROVIDE SAMPLE

Running the tests

npm test

Built With

• zeebe-node - nodejs client for Zeebe
• camunda-external-task-client-js - nodejs client for Camunda BPM
• inversify - Dependency injection
• opentelemtry - add instrumentation (provides a single set of APIs, libraries to capture distributed traces)

Philosophy

1. Allow Javascript developers to write code that adheres to the SOLID principles.
2. Facilitate and encourage the adherence to the best OOP and IoC practices.
3. Add as little runtime overhead as possible.

Kubernetes

Zeebe

kubernetes/run

Docker

Zeebe

In your terminal

docker/run

Bpmn platform

docker run -d --name camunda -p 8080:8080 camunda/camunda-bpm-platform:latest
// Go: http://localhost:8080/camunda - user/password : `demo/demo`

More details

TODO

• Add tests
• Improve docs
• Make sample and confirm compatibility with DMN
• Adding a common exception error codes between Manager clients
• Add metrics by using prometheus lib

Versionning

We use SemVer for versioning. For the versions available, see the tags on this repository.

workit-camunda | Zeebe | Camunda BPM -- | -- | -- >=4.0.5 | 0.22.1 | 7.6 to latest 3.2.x <=4.0.4 | 0.20.x < 0.20.1 | 7.6 to latest 2.2.0 | 0.20.x | 7.6 to latest 2.1.0 | 0.19.x | 7.6 to latest 2.0.1 | 0.18.x | 7.6 to latest < 1.0.0 | <= 0.17.0 | 7.6 to latest

Maintainers

See the list of contributors who participated in this project.

Contributing

Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.

License

This project is licensed under the MIT License - see the LICENSE file for details

Acknowledgments

• Josh Wulf - zeebe-node inspired me during workit-cli development