Service Orchestrator

Service orchestrator without the boilerplate.

Workflow Architecture

Each endpoint of the orchestrator is defined with a workflow. A workflow has discrete configuratable steps with narrowly-defined responsibility.

Through configuration, a request to the workflow can mapped to a request to a service. The response from the service can mapped to the response returned by the workflow:

flowchart LR
    request --> mapRequest
    mapRequest --> service
    service --> mapResponse
    mapResponse --> response
    
    subgraph Workflow
        direction LR
        mapRequest["map"]
        mapResponse["map"]
    end

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In addition to external services, local transform functions can be defined to create new values from workflow requests, service responses, and transform output. The output of transforms can be mapped to service requests or workflow responses just like service responses:

flowchart LR
    transformRequest["transform"]
    mapRequest["map"]
    transformResponse["transform"]
    mapResponse["map"]

    request --> transformRequest
    request --> mapRequest
    mapRequest --> service
    service --> transformResponse
    service --> mapResponse
    mapResponse --> response
    
    subgraph Workflow
        direction LR
        transformRequest --> mapRequest
        transformResponse --> mapResponse
    end

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The values from a service response can be used as part of the request to another service.

flowchart LR
    mapRequest["map"]
    serviceB["service"]

    request --> transform
    serviceB --> transform
    mapRequest --> service

    subgraph Workflow
        direction LR
        serviceB --> mapRequest
        transform --> mapRequest
    end

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Overall Architecture

1. Provide Open API specifications for orchestrator endpoints and dependent services
2. Create workflow specifications using domain-specific language

Given a Workflow Request/Response:

Request
    input 1
    input 2
Response
    output 1
    output 2
    output 3

And a service called Service A with Request/Response:

Request
    input A
Response
    output A
    output B

And a service called Service B with Request/Response:

Request
    input A
    input B
Response
    output A

Potential Example of Workflow Specification:

Workflow A:
    transform:
        inputSum:
            add:
                - input 1
                - input 2
    Service A:
        input A: inputSum
    Service B:
        input A: "Service A: output B"
        input B: input 2
    response:
        output1: "Service B: output A"
        output2: "Service A: output A"
        output3: "Service A: output B"

The sequence diagram of Workflow A:

sequenceDiagram
    API Consumer ->> Workflow: input 1, input 2

    Workflow ->> Service A: add(input 1, input 2)
    Service A -->> Workflow: output A, output B

    Workflow ->> Service B: Service A: output B, input 2
    Service B -->> Workflow: output A

    Workflow -->> API Consumer: Service B: output A, Service A: output A, Service A: output B

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The sequence diagram with example concrete values:

sequenceDiagram
    API Consumer ->> Workflow: 1, 2

    Workflow ->> Service A: add(1, 2) = 3
    Service A -->> Workflow: 10, 11

    Workflow ->> Service B: 11, 2
    Service B -->> Workflow: 20

    Workflow -->> API Consumer: 20, 10, 11

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