Flow Execution

A Contextual agent is the host process for the execution of a Node-RED flow. Node-RED runs on a single-threaded event loop (like Node.js) but can handle multiple concurrent operations through non-blocking asynchronous callbacks.

However, the Agent-type (HTTP or Event) determines whether multiple requests can be handled concurrently. HTTP agents can handle multiple concurrent operations, but Event agents handle one message at a time received from the message service.

While the agent process hosts the Node-RED flow, it also interfaces to other Contextual services such as the logging service. This allows you to use Log-tap nodes in your flows which emit data which is then sent to the logging service by the Agent.

Similarly, it is the agent software outside of Node-RED that receives incoming events and injects them into the flow at the apporpriate input node.

And while you can catch errors within your flow using a Catch Node, the agent itself will catch any uncaught errors and log them to the logging service, allowing you to further diagnose problems with your flows.