Custom Nodes in python

[avasquezkudaw]

Hi guys, I’m trying to create a custom_handler for custom nodes in Python, following examples written in Go (https://github.com/gorules/go-custom-nodes/blob/master/backend/main.go).

engine := zen.NewEngine(zen.EngineConfig{
		CustomNodeHandler: nodes.CustomNodeHandler,
	})

	decision, err := engine.CreateDecision(request.Content)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	result, err := decision.Evaluate(request.Context)
	if err != nil {
		var res gin.H
		if err := json.Unmarshal([]byte(err.Error()), &res); err == nil {
			c.JSON(http.StatusBadRequest, res)
			return
		}

		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"result":      result.Result,
		"trace":       result.Trace,
		"performance": result.Performance,
	})

However, I can't find documentation or methods to achieve this. I was able to create the custom nodes in the UI, but in the Python backend, I can’t get them to work, and when loading the graph with these custom nodes, I get the following error:

import zen, json
ze = zen.ZenEngine()
de = ze.create_decision(json.dumps({"contentType": "application/vnd.gorules.decision", "nodes": [{"type": "customNode", "content": {"kind": "mathAdd"}, "id": "f3cc69ea-324f-456b-9af0-2469e1461393", "name": "mathAdd1", "position": {"x": 550, "y": 205}}, {"type": "inputNode", "id": "4d57711f-a141-4a3a-8f52-42ede085fdac", "name": "request", "position": {"x": 265, "y": 105}}, {"type": "outputNode", "id": "0a14e0a6-bd71-4747-bcc5-64964fc39a87", "name": "response", "position": {"x": 885, "y": 215}}], "edges": [{"id": "6d2ee81e-0447-4cfb-b120-5181065488b8", "sourceId": "4d57711f-a141-4a3a-8f52-42ede085fdac", "type": "edge", "targetId": "f3cc69ea-324f-456b-9af0-2469e1461393"}, {"id": "1e13a8e6-0591-4197-90ee-7974fd2a41ca", "sourceId": "f3cc69ea-324f-456b-9af0-2469e1461393", "type": "edge", "targetId": "0a14e0a6-bd71-4747-bcc5-64964fc39a87"}]}))

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: Failed to serialize decision content

Caused by:
    missing field `config` at line 1 column 216

How can I approach this issue?

Thanks in advance. Best regards.

[mbollemeijer]

Same for the rust custom nodes.
Examples in each language would help a lot.

[avasquezkudaw]

Hi everyone,

After multiple trials and errors and looking at examples from other languages, I managed to get a custom_handler for custom_node working in Python.

Here’s an example of the custom node in React:

import { createJdmNode } from '@gorules/jdm-editor';
import { PartitionOutlined } from '@ant-design/icons';

export const addNode = createJdmNode({
  kind: 'decision' as string,
  group: 'Decision',
  icon: <PartitionOutlined />,
  displayName: 'Decision',
  shortDescription: 'Call decision',
  inputs: [
    { label: 'Rule UUID', name: 'uuid', control: 'text' }, 
  ]
});

And here’s the Python code that handles the custom_handler for custom_node:

import zen
import json

class Decision():
    def handle(self, request):
        uuid = request.get_field("uuid")
        # uuid = request.input.get('uuid')
        return {
            "output": { "decision": uuid }
        }

custom_nodes = {
    "decision": Decision(),
}

def custom_node_handler(request):
    node_kind = request.node.get("kind")
    node_handler = custom_nodes.get(node_kind)
    if not node_handler:
        raise ValueError("Component not found")
    return node_handler.handle(request)

decision_engine = zen.ZenEngine({ "customHandler": custom_node_handler })

graph_dict = {
    'nodes': [
        {'id': '115975ef-2f43-4e22-b553-0da6f4cc7f68', 'type': 'inputNode', 'position': {'x': 120, 'y': 170}, 'name': 'Request'},
        {'id': 'db8797b1-bcc1-4fbf-a5d8-e7d43a181d5e', 'type': 'outputNode', 'position': {'x': 805, 'y': 175}, 'name': 'Response'},
        {'type': 'customNode', 'content': {'kind': 'decision', 'config': {'uuid': '123'}}, 'id': '27b70590-3eba-4781-8539-9bae453a68ac', 'name': 'Call Decision', 'position': {'x': 455, 'y': 180}}
    ],
    'edges': [
        {'id': 'a3069180-68e2-4ec5-a2ae-6eed22c11df2', 'sourceId': '115975ef-2f43-4e22-b553-0da6f4cc7f68', 'type': 'edge', 'targetId': '27b70590-3eba-4781-8539-9bae453a68ac'},
        {'id': '3dd50c50-8f73-439b-9f1c-4469b925f775', 'sourceId': '27b70590-3eba-4781-8539-9bae453a68ac', 'type': 'edge', 'targetId': 'db8797b1-bcc1-4fbf-a5d8-e7d43a181d5e'}
    ]
}

graph = json.dumps(graph_dict)
dec = decision_engine.create_decision(graph)

result = dec.evaluate({"a": 1}, opts={"trace": True, "max_depth": None})

print(result)

I hope this can help other developers and eventually expand this functionality.

Best regards to everyone.