Tutorial: Building Your First Workflow

This tutorial will guide you through the process of building a simple Junjo workflow from scratch. We will build the same workflow that is in the Installation guide, but we will do it step-by-step to better understand how each component works.

Step 1: Define the State

First, we need to define the shape of our workflow’s state. We’ll use a Pydantic model that inherits from BaseState.

from junjo import BaseState

class SampleWorkflowState(BaseState):
    count: int | None = None
    items: list[str]

Step 2: Create the Store

Next, we’ll create a BaseStore to manage our state. This store will have one action, set_count, which we’ll use to update the count field in our state.

from junjo import BaseStore

class SampleWorkflowStore(BaseStore[SampleWorkflowState]):
    async def set_count(self, payload: int) -> None:
        await self.set_state({"count": payload})

Step 3: Create the Nodes

Now, let’s create the nodes that will perform the work of our workflow. We’ll create five nodes:

• FirstNode: The entry point of our workflow.

• CountItemsNode: Counts the items in the state and updates the count.

• EvenItemsNode: A node that will be executed if the count is even.

• OddItemsNode: A node that will be executed if the count is odd.

• FinalNode: The exit point of our workflow.

from junjo import Node

class FirstNode(Node[SampleWorkflowStore]):
    async def service(self, store: SampleWorkflowStore) -> None:
        print("First Node Executed")

class CountItemsNode(Node[SampleWorkflowStore]):
    async def service(self, store: SampleWorkflowStore) -> None:
        state = await store.get_state()
        items = state.items
        count = len(items)
        await store.set_count(count)
        print(f"Counted {count} items")

class EvenItemsNode(Node[SampleWorkflowStore]):
    async def service(self, store: SampleWorkflowStore) -> None:
        print("Path taken for even items count.")

class OddItemsNode(Node[SampleWorkflowStore]):
    async def service(self, store: SampleWorkflowStore) -> None:
        print("Path taken for odd items count.")

class FinalNode(Node[SampleWorkflowStore]):
    async def service(self, store: SampleWorkflowStore) -> None:
        print("Final Node Executed")

Step 4: Create the Condition

We need a Condition to create a branch in our workflow. This condition will check if the count in our state is even.

from junjo import Condition

class CountIsEven(Condition[SampleWorkflowState]):
    def evaluate(self, state: SampleWorkflowState) -> bool:
        count = state.count
        if count is None:
            return False
        return count % 2 == 0

Step 5: Assemble the Graph in a Factory

Now we’ll bring everything together in a Graph. We’ll create a graph_factory function that instantiates all of our nodes and assembles them into a Graph.

from junjo import Edge, Graph

def create_graph() -> Graph:
    """
    Factory function to create a new instance of the sample workflow graph.
    This ensures that each workflow execution gets a fresh, isolated graph,
    preventing state conflicts in concurrent environments.
    """
    # Instantiate the nodes
    first_node = FirstNode()
    count_items_node = CountItemsNode()
    even_items_node = EvenItemsNode()
    odd_items_node = OddItemsNode()
    final_node = FinalNode()

    # Create the workflow graph
    return Graph(
        source=first_node,
        sink=final_node,
        edges=[
            Edge(tail=first_node, head=count_items_node),
            Edge(tail=count_items_node, head=even_items_node, condition=CountIsEven()),
            Edge(tail=count_items_node, head=odd_items_node),
            Edge(tail=even_items_node, head=final_node),
            Edge(tail=odd_items_node, head=final_node),
        ]
    )

Step 6: Create and Execute the Workflow

Finally, we’ll create a Workflow instance and execute it. We’ll pass our graph_factory and a store_factory to the Workflow constructor. The store_factory will create a new instance of our SampleWorkflowStore with some initial data.

from junjo import Workflow
import asyncio

async def main():
    # Create the workflow
    sample_workflow = Workflow[SampleWorkflowState, SampleWorkflowStore](
        name="Getting Started Example Workflow",
        graph_factory=create_graph,
        store_factory=lambda: SampleWorkflowStore(
            initial_state=SampleWorkflowState(
                items=["laser", "coffee", "horse"]
            )
        )
    )

    # Execute the workflow
    await sample_workflow.execute()
    print("Final state: ", await sample_workflow.get_state_json())

if __name__ == "__main__":
    asyncio.run(main())

Congratulations! You’ve built your first Junjo workflow. You can now run this file and see the output in your console.