Core Concepts

Nodes, edges, delivery modes, and how they fit together.

The flow graph

A FlowDSL document describes a directed acyclic graph (DAG). Nodes are the vertices; edges are the directed connections between them.

text

ValidateOrder → ChargePayment → FulfillOrder → NotifyCustomer

The JSON/YAML document is always the source of truth. The visual canvas is a projection.

Nodes

A node is a unit of business logic. It has no knowledge of how its output is delivered — that is the edge's responsibility.

yaml

nodes:
  ChargePayment:
    operationId: charge_payment
    description: Charges the customer's payment method

Naming conventions:

Node component names → PascalCase
operationId values → snake_case

Edges

An edge connects two nodes and carries a delivery policy.

yaml

edges:
  - from: ChargePayment
    to: FulfillOrder
    delivery:
      mode: checkpoint
      packet: "asyncapi#/components/messages/PaymentConfirmed"

The delivery.mode field determines the transport and durability guarantee.

Packets

A packet is an AsyncAPI message reference. FlowDSL never duplicates message schemas — it references them:

yaml

packet: "asyncapi#/components/messages/OrderFulfilled"

The runtime

The FlowDSL runtime reads the graph definition and:

Starts each node's handler
Wires up the transport layer according to each edge's delivery policy
Handles retries, checkpointing, and replay automatically

Your business logic never touches transport code.

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Contributing

How to contribute to FlowDSL — spec, SDKs, Studio, and documentation.

Checkpoints

How the checkpoint delivery mode enables pipeline resumption after failure in FlowDSL.