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Imixs-Micro

Imixs Micro is a lightweight distributed workflow management system based on the Imixs-Workflow technology. This system can be used, for example, as a workflow service in an industrial production plant.

Architecture Overview

This repository contains the architecture and implementation details for a distributed workflow management system designed for industrial applications. The system consists of an enterprise-process-management layer and multiple micro-process-management layers used in production workstations. The messaging between the different services is utilizing a combination of WebSocket communication and REST APIs for efficient and scalable operations.

Key Components

  1. Enterprise-Process Server

    • Runs Imixs-Workflow engine on a Jakarta EE server
    • Manages high-level processes (e.g., customer orders)
    • Communicates with workstations via WebSockets and REST

  2. Micro-Process Workstations

    • Raspberry Pi-based interfaces for production equipment
    • Running lightweight Imixs-Workflow Micro Kernel for local process management
    • Communicate with Enterprise-Process server and other workstations

Communication Patterns

The goal of the messaging between the Enterprise-Process Server and the Workstations is bi-directional messaging pattern. To start a new production processes on dedicated workstation based on the model definition, the Enterprise-Process Server opens a WebSocket connection to the workstation. To signal the completion of a production process the workstation sends a Message via Rest API to the Enterprise-Process service. Furthermore a Workstation can start processes on other Workstations in Bidirectional message flow based on WebSockets only.

Enterprise-Process → Workstation

  • Direction: Unidirectional (Enterprise-Process → Workstation )
  • Technology: WebSockets
  • Purpose: Rapid distribution of production orders
  • Implementation: Quarkus with jakarta.websocket API

Workstation → Enterprise-Process

  • Direction: Unidirectional (Workstation → Enterprise-Process)
  • Technology: REST API
  • Purpose: Status updates and process completion notifications
  • Implementation: Utilizing existing Imixs-Workflow REST API

Workstation → Workstation

  • Direction: Bidirectional
  • Technology: WebSockets
  • Purpose: Fast, real-time communication for short-lived sub-processes
  • Implementation: Quarkus with jakarta.websocket API

Implementation Details

Enterprise-Process Server (Jakarta EE)

  1. WebSocket Client

    • Implemented using jakarta.websocket API
    • Sends production orders to workstations

  2. REST API Endpoints

    • Existing Imixs-Workflow REST API
    • Receives status updates and process completion notifications from workstations

Workstation (Raspberry Pi with Quarkus)

  1. WebSocket Server

    • Implemented using jakarta.websocket API via Quarkus
    • Receives production orders from Enterprise-Process server

  2. WebSocket Client and Server

    • For workstation-to-workstation communication
    • Implemented using jakarta.websocket API via Quarkus

  3. REST Client

    • Implements calls to Imixs-Workflow REST API on Enterprise-Process server
    • Sends status updates and process completion notifications

Key Advantages

  1. Efficiency: Fast distribution of production orders via WebSockets
  2. Simplicity: Streamlined implementation on resource-constrained workstations
  3. Scalability: Efficient handling of multiple workstations
  4. Flexibility: Tailored communication patterns for different interaction types

Implementation Considerations

  1. Error Handling: Robust mechanisms for WebSocket connection failures
  2. Connection Management: Auto-reconnect for WebSocket connections on workstations
  3. Security: Proper authentication and authorization for all communication channels

How to Get Started

You can test Imixs-Micro with Docker. The project provides a docker compose setup to simulate a test environment with a Enterprise Workflow Server and three workstations.

Build

First make sure to build the project with:

$ ./imixs-micro-engine/mvnw clean package -Dquarkus.container-image.build=true

To command will build the docker image to simulate a workstation.

To build the client code you can run:

$ mvn clean install

Start

Now you can start the test environment with:

docker compose up

This will start the Enterprise Workflow server and tree workstations.

    ╭────────────────────────────╮     
    │ Enterprise Workflow Server │   
    │   Imixs-Process Manager    │  
    ╰──────┬────────────────┬──┬─╯ 
           │ Web Socket     │  │      Web Socket 
           │                │  ╰─────────────>>──────────╮
     ╔═╧═╧═╧═╧═╧═╧═══╗    ╔═╧═╧═╧═╧═╧═╧═══╗        ╔═╧═╧═╧═╧═╧═╧═══╗
     ║ Workstation-1 ║    ║ Workstation-2 ║        ║ Workstation-3 ║
     ║  Raspberry Pi ║    ║ Raspberry Pi  ║        ║ Raspberry Pi  ║     
     ╚═╤═╤═╤═╤═╤═╤═══╝    ╚═╤═╤═╤═╤═╤═╤═══╝        ╚═╤═╤═╤═╤═╤═╤═══╝
       │                      │       ╰──────<<──>>────────╯ 
       │                      │            Web Socket (Bidirectional)     
    ╭──┴─────╮             ╭──┴─────╮                 
    │Sensor-1│             │Sensor-2│   
    ╰────────╯             ╰────────╯

You can test the docker status with the command docker ps

$ docker ps
CONTAINER ID   IMAGE                                COMMAND                  CREATED              STATUS              PORTS                                                                                                                             NAMES
2fec832b21c4   imixs/imixs-micro-engine:latest      "java -jar /deployme…"   About a minute ago   Up About a minute   8443/tcp, 0.0.0.0:8082->8080/tcp, [::]:8082->8080/tcp                                                                             imixs-micro-workstation-2-1
2f6c8548b6c5   imixs/imixs-micro-engine:latest      "java -jar /deployme…"   About a minute ago   Up About a minute   8443/tcp, 0.0.0.0:8083->8080/tcp, [::]:8083->8080/tcp                                                                             imixs-micro-workstation-3-1
8530ae17c165   imixs/imixs-micro-engine:latest      "java -jar /deployme…"   About a minute ago   Up About a minute   8443/tcp, 0.0.0.0:8081->8080/tcp, [::]:8081->8080/tcp                                                                             imixs-micro-workstation-1-1
450c33d928a5   postgres:13.11                       "docker-entrypoint.s…"   6 days ago           Up About a minute   5432/tcp                                                                                                                          imixs-micro-imixs-db-1
85674cfa3e4e   imixs/imixs-process-manager:latest   "/opt/jboss/wildfly/…"   6 days ago           Up About a minute   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp, 0.0.0.0:8787->8787/tcp, :::8787->8787/tcp, 0.0.0.0:9990->9990/tcp, :::9990->9990/tcp   imixs-micro-imixs-app-1

Test

You can now login to the Enterprise Workflow server from your Web Browser: http://localhost:8080

Use the user id 'admin' and the password 'adminadmin'. You will see the Imixs-Process Manager Web Interface where you can upload your workflow models.

Next go to "Models" and upload the model order-1.0.0.bpmn from the /workflow directory

Now you can start a new "Customer Order" workflow: