Flowable External Worker Library for .NET

An External Worker Task in BPMN or CMMN is a task where the custom logic of that task is executed externally to Flowable, i.e. on another server. When the process or case engine arrives at such a task, it will create an external job, which is exposed over the REST API. Through this REST API, the job can be acquired and locked. Once locked, the custom logic is responsible for signalling over REST that the work is done and the process or case can continue.

This project makes implementing such custom logic in .NET easy by not having the worry about the low-level details of the REST API and focus on the actual custom business logic. Integrations for other languages are available, too.

This project is still a work-in-progress client, expect that the API will change.

Authentication

This library uses the AuthenticationHeaderValue class to provide the authentication. This allows to provide a Bearer token as well as Basic authentication by providing the correct parameters.

Installation

To install the external worker library, execute the following command:

dotnet add package Flowable.ExternalWorkerClient

Sample

Cloud

The usage with Flowable Cloud is simpler, since everything is pre-configured. However, it's required to either use the user credentials or to pre-configure a personal access token.

using System.Net.Http.Headers;
using FlowableExternalWorkerClient.Client;
using FlowableExternalWorkerClient.Rest;

var auth = new AuthenticationHeaderValue("Bearer", "<personal-access-token>");

var externalWorkerClient = new ExternalWorkerClient(authentication: auth);
var subscription = externalWorkerClient.Subscribe("myTopic", new HandleJobs());

// Keep the application running
Console.WriteLine("Waiting for external worker jobs. Press Enter to exit...");
Console.ReadLine();

class HandleJobs : IExternalWorkerCallbackHandler
{
    public IWorkResult Handle(ExternalWorkerAcquireJobResponse job, IWorkResultBuilder work)
    {
        Console.WriteLine("Handle job: " + job.Id);
        return work
            .Success()
            .Variable("testVar", "Hello from C#");
    }
}

Local

The following is an example how you can connect to a Flowable instance running at http://localhost:8090 and process all messages retrieved on the topic myTopic:

using System.Net.Http.Headers;
using System.Text;
using FlowableExternalWorkerClient.Client;
using FlowableExternalWorkerClient.Rest;

var auth = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.UTF8.GetBytes("admin:test")));

var externalWorkerClient = new ExternalWorkerClient(flowableHost: "http://localhost:8090/flowable-work", authentication: auth);
var subscription = externalWorkerClient.Subscribe("myTopic", new HandleJobs());

// Keep the application running
Console.WriteLine("Waiting for external worker jobs. Press Enter to exit...");
Console.ReadLine();

class HandleJobs : IExternalWorkerCallbackHandler
{
    public IWorkResult Handle(ExternalWorkerAcquireJobResponse job, IWorkResultBuilder work)
    {
        Console.WriteLine("Handle job: " + job.Id);
        return work
            .Success();
    }
}