Router mechanism technical explanation

An article on how the Content-Based Routing technicaly mechanism works.

How it works?

Here is the sample integration flow with CBR inside it:

Click to expand:

{
    "data": {
        "attributes": {
            "name": "CBR Test",
            "type": "ordinary",
            "graph": {
                "nodes": [
                    {
                        "command": "platform/webhook:receive@latest",
                        "fields": {
                            "payload": "test"
                        },
                        "id": "in"
                    },
                    {
                        "command": "platform/router:route@latest",
                        "id": "router"
                    },
                    {
                        "command": "platform/code:execute@latest",
                        "fields": {
                            "code": "this.logger.info('one');emitter.emit('data',msg)"
                        },
                        "id": "one"
                    },
                    {
                        "command": "platform/code:execute@latest",
                        "fields": {
                            "code": "this.logger.info('two');emitter.emit('data',msg)"
                        },
                        "id": "two"
                    },
                    {
                        "command": "platform/code:execute@latest",
                        "fields": {
                            "code": "this.logger.info('default');emitter.emit('data',msg)"
                        },
                        "id": "default"
                    }
                ],
                "edges": [
                    {
                        "source": "in",
                        "target": "router"
                    },
                    {
                        "config": {
                            "condition": "$number(test) > 10"
                        },
                        "source": "router",
                        "target": "one"
                    },
                    {
                        "config": {
                            "condition": "$number(test) > 20"
                        },
                        "source": "router",
                        "target": "two"
                    },
                    {
                        "source": "router",
                        "target": "default"
                    }
                ]
            }
        },
        "type": "flow"
    }
}

The content based router (CBR) component has a single input and multiple outputs (edges). Outgoing edge from CBR component should have a configuration property called condition that defines a JSONata expression. Expression on each edge is validated based on message that arrived to the CBR component. If condition is evaluated to true then a copy of the message is sent to the component connected to the outgoing edge.

If condition is not defined on the outgoing edge, then this edge considered to be default edge. Default edge will get all messages that didn’t matched any other edges. Please note - CBR component may only have a single default edge. Multiple default edges will fail validation of elastic.io API.

Now let us examine our sample from above:

Incoming webhook has a message like

    {
        "test":"12345"
    }

As you can see CBR component has 3 outgoing edges, conditions are
$number(test) > 10 for edge that is connected to step ID one
$number(test) > 30 for edge that is connected to step ID two
Last edge has no condition, therefore a default edge connected to step default

For more information please visit our Content-Based Routing page.

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