Client

The SHAR client library performs the following roles:

Provides a BPMN parser which converts BPMN to a SHAR state machine.
Provides a programmatic interface to the SHAR API.
Facilitates Service Task and Workflow Message registration.
Listens for registered Service Task and Workflow Messages.
Decodes and encodes workflow variables.

API calls

The following diagram shows the message flow between SHAR Client and the Engine.

sequenceDiagram
autonumber
    participant Client 
    participant NATS
    participant SHAR API
    participant Engine
    Client--)NATS: WORKFLOW.Api.LaunchWorkflow(request)
    activate Client
    NATS--)SHAR API: WORKFLOW.Api.LaunchWorkflow(request)
    activate SHAR API
    SHAR API->>Engine: launchWorkflow(*model.LaunchWorkflowRequest)
    SHAR API--)NATS: WORKFLOW.Api.LaunchWorkflow(response)
    deactivate SHAR API
    NATS--)Client: WORKFLOW.Api.LaunchWorkflow(response)
    deactivate Client

In reality the request and response routing are transparent to the SHAR client, as they are handled by the NATS client and appear as a blocking call similar to GRPC.

BPMN Parser

The BPMN Parser converts a BPMN file into a SHAR state machine model.

Neither the SHAR API nor the SHAR Engine understand anything about BPMN. The client is the only point of contact with the BPMN file content.

Currently the client supports parsing Camunda Modeler 8 BPMN files created by the Camunda Modeler. Most of the functionality from the modeler is supported including running sub-workflows and input and output transformation for variables.

The syntax for all business expressions and scripts in SHAR is Expr. The Camunda Modeler uses another expression language, and may therefore incorrectly flag expressions as invalid. This will be fixed with the release of the SHAR modeler.

All types used in variables passed to workflows must be primitive go types eg. string, int, []int, map[string]string. Although the workflow engine is capable of operating with user defined structs, the serializer and deserializer will not understand how to handle them.