Flow

A Flow is the runtime representation of a graph: it owns the nodes, the links between them, the initial information packets (IIPs) and the state of execution.

The Flow class is built from a FlowDefinition, which is the same model used by the flow files themselves:

type: flow
nodes:
  - id: Log
    title: Log
    ns: console
    name: log
links:
  - source:
      id: Request
      port: request
    target:
      id: EndRequest
      port: request
providers:
  '@':
    path: './{ns}.{name}.yml'

Creating a flow

const Flow = require('@fbpx/flow').Flow

const flow = await Flow.create('my-flow', flowDefinition)

Nodes, links and IIPs

flow.addNode(node, nodeDefinition)
flow.removeNode(nodeId)

flow.addLink(link)
flow.removeLink(link)

flow.createIIP(iipDefinition)   // create an IIP
flow.connectIIP(iip)            // connect it to a port
flow.sendIIPs(iipDefinitions)   // create and connect a set of IIPs
flow.clearIIP(iip)

An IIP can be marked cyclic — the equivalent of the => arrow in a .fbp file — which opens a batch, delivers each element of an array separately, and closes it (end-of-stream). This is what feeds a streaming node or a >= collector a finite stream:

flow.sendIIPs([{id: 'feed', port: 'in', data: ['a', 'b', 'c'], setting: {cyclic: true}}])

A plain (non-cyclic) IIP writes one packet and never closes a batch. See Streams for the semantics.

Execution

flow.run()      // run the graph
flow.stop()     // stop execution
flow.reset()    // reset counters and state

A flow is either active (running) or stopped. runCount tracks how many times the flow has run.

Ports

A flow exposes external ports in the same way a node does:

Ports can be added and removed at runtime with addPort and removePort.