Workflows help you automate business processes in a standardized manner, bridging the gap between expressing and modelling business logic.

Workflow definitions are written based on the Serverless Workflow pecification. For CNC Workflow Automation, only a subset of the full specification is supported. This chapter describes all the supported features and gives practical examples for many of them.

A new workflow can be defined in JSON format. The structure of the workflow definition is described in the Serverless Workflow specification.

The supported high-level components are as follows:

• id

• name

• description

• version

• start

• retries

• errors

• functions

• states

• metadata

States define the building blocks of workflow execution logic. Different types of states provide control flow logic to the Execution Engine and also allow you to define which activities to execute.

The serverless workflow specification permits operation states to define sets of actions to be executed in sequence or parallel. CNC Workflow Automation supports execution of actions in sequence only.

An specification defines invocation of three different types of services:

• Execution of function definition. This is the only type of service that CNC Workflow Automation currently supports.

• Execution of another workflow definition as a child workflow. This is not supported in the current implementation.

• Referencing events that may be "produced" or "consumed". This is not supported in the current implementation.

Switch states enable you to define decision points to route the workflow to a given path based on certain conditions. The Serverless Workflow specification supports both data-based conditions and event-based conditions. CNC Workflow Automation supports data-based conditions only.

Sleep state pauses workflow execution for a given duration.  

    {
        "name": "Sleep3Minutes",
        "type": "sleep",
        "duration": "PT3M",
        "transition": {
            "nextState": "NextState"
        }
    }

Use Inject state to inject static data into the State Data.

    {
        "id": "example",
        "version": "1.0",
        "specVersion": "0.9",
        "start": "HelloWorld",
        "states": [
            {
                "name": "HelloWorld",
                "type": "inject",
                "data": {
                    "name": "Cisco",
                    "message": "Hello World"
                },
                "stateDataFilter":{
                    "output": "${ .message + \" from \" + .name + \"!\"  }"
                },
                "end": {
                    "terminate": "true"
                }
            }
        ]
    }

ForEach state allows you to define a set of actions to execute for each element in an array or list defined in State Data. For example, for each device in device array, check that the devices are in sync. While the serverless workflow specification defines support for Parallel and Sequential execution of actions, current implementation only supports sequential execution of actions for each element in array.

    {
        "id": "example",
        "version": "1.0",
        "specVersion": "0.9",
        "start": "InjectData",
        "functions": [
            {
                "name": "HelloWorld",
                "operation": "HelloWorld"
            }
        ],
        "states": [
            {
                "name": "InjectData",
                "type": "inject",
                "data": {
                    "people": [
                        {
                            "Firstname": "Peter",
                            "Surname": "Parker"
                        },
                        {
                            "Firstname": "Thor",
                            "Surname": "Odinson"
                        },
                        {
                            "Firstname": "Bruce",
                            "Surname": "Banner"
                        }
                    ]
                },
                "transition":{
                    "nextStat": "SayHelloToEveryone"
                }
            },
            {
                "name": "SayHelloToEveryone",
                "type": "foreach",
                "inputCollection": "${ .people }",
                "iterationParam": "person",
                "outputCollection": "${  .messages }",
                "actions": [
                    {
                        "name": "SayHello",
                        "functionRef":{
                            "refName": "HelloWorld",
                            "arguments": {
                                "name": "${ .person.Firstname + \" \" + .person.Surname }"
                            }
                        }
                    }
                ],
                "end": {
                    "terminate": "true"
                }
            }
        ]
    }
 

Parallel state allows you to define a collection of branches that are executed in parallel. Each branch in a state can define its own set of actions. Once the execution has completed, the parallel branches are joined into current path based on the completionType attribute.

The completionType attribute can define two values:

• allOf: All branches must complete execution before state can transition/end. This is the default value.

• atLeast: State can transition/end if the number of branches specified in atLeast has completed execution. If completionType attribute is "atLeast", numCompleted must also be set.

State data plays an important role during the lifecycle of the workflow. A state can filter data, inject data, and add data. Jq plays an important role in data filtering, creation and manipulation. For more information on how data can be handled, see the Serverless Workflow specification.

When creating workflows in CNC, the following data management rules apply:

• Initial data passed into workflow execution is passed into State data as input.

• Data output from the last executed state is workflow output.

• If no State Input Filter is specified, all the data is passed into the state.

• If no State Output Filter is specified, all the data is passed into the next state. 

• Workflow expressions in jq allow you to filter and manipulate data.

• Actions also allow for filtering data and also, if return data from action should be merged back into state data.

• Filters must return JSON objects. If a jq workflow expression results in a string literal, this will result in an error. 

• When working with jq, it is highly recommended to use https://jqplay.org/ to test the jq expressions. Alternatively, you can download jq locally and use it for testing.