Best practices to handle errors in node-red


Node-RED is a well-liked and effective tool for building intricate workflows and automating processes. Yet, given the number of nodes and connections, faults frequently happen and might potentially stop the flow of data. The usage of error handling nodes, how to detect and resolve faults, and how to adopt best practices for error prevention constitute a few of the best methods to handle mistakes in Node-RED that will be covered in this article. You may use these tricks and strategies to use Node-RED to build processes that are more dependable and effective.

Ways to handle errors in node-red

1. Use Debug Nodes

  • Node-RED employs debug nodes to display and trace data flow at various points in your flow. They help you identify possible trouble areas and determine yet if the data matches your expectations. Debug nodes can display the output of a single node or the output of the whole flow.

  • To add a debug node in Node-RED, simply click and drag the Debug node from the Node-RED Palette onto your workspace. By default, the Debug node outputs the full message object. One can, however, choose to display certain elements of the message, such as the payload or specified characteristics, by picking the appropriate choice in the Debug node configuration.

  • When you've added a Debug node to your flow, you may attach it to an individual single node or the entire flow's output. A Debug node will display its output data as it travels and through the linked node or the complete flow whenever the flow is running. The Debug node can be additionally configured to report data to the Node-RED Debug tab or the Node-RED Console.

2. Error Handling Nodes

  • In Node-RED, error-handling nodes are used to manage errors and exceptions that may arise during the execution of a flow. They give a method for elegantly catching and handling mistakes rather than crashing the entire flow or application.

  • Node-RED has various error-handling nodes, including Catch, Status, and Complete.

    • The Catch node is intended to capture and manage errors that occur while a flow is being executed. It may be used to detect certain sorts of mistakes, such as missing input or an incorrect API response. When an issue is detected, the Catch node may be set to perform specified actions, such as sending an email message or recording the problem in a file.

    • The Status node displays the current state of a flow or a single node. It may be set to show the node's status dependent on the success or failure of the previous node in the flow. This can assist detect nodes that aren't working correctly or where mistakes are occurring.

    • The Complete node indicates that a flow has been successfully finished. It can be used to tell external systems that a procedure, such as sending a message to a user or starting another process, has concluded.

3. Logging

  • Node-RED has a logging function that allows you to log errors and events in one place. Depending on your requirements, you can record errors to a file, Syslog, or database. This aids in determining the root cause of an issue, particularly in production contexts.

  • Node-RED has various built-in logging nodes that allow developers to log messages and faults created by their flows. In Node-RED, logging nodes are used to store and retrieve flow information such as errors, warnings, and debugging information.

  • The following are some of the logging nodes available in Node-RED −

    • The Debug node is the most often used Node-RED node for logging. It enables programmers to transmit debugging data to the Node-RED editor's debug tab. The Debug node may be set up to provide details about a certain flow, a particular node, or the whole flow.

    • Log Node − Messages are written to the system log using the Log node. It can be used to record significant occurrences like the beginning or end of a flow or the occurrence of an error.

    • File Node − Messages are written to files using the File node. It can be put to use to produce logs that can be later evaluated, as well as to store critical events or debug information.

    • MQTT Node − Messages are published to an MQTT broker using the MQTT node. It is possible to utilize it to transmit logging data to a distant server or to start additional activities based on the logging data.

4. Testing

  • Testing is a crucial step in the development of any software system, including Node-RED flows. Proper testing helps ensure that the flows are working as expected and can detect and handle errors correctly. There are several ways to test Node-RED flows to ensure error handling is working as intended.

    • Node-RED has an input injection functionality that enables programmers to insert test messages right into a flow. This may be used to verify the flow's error-handling skills and imitate real-world events.

    • Developers can consciously include nodes that produce mistakes in their flows to evaluate the ability to handle faults. This can be achieved by including nodes that randomly produce mistakes or by purposefully causing the input data to be in the wrong format.

    • Unit testing frameworks like Mocha and Chai may be used to test Node-RED flows. These frameworks may be used to test each node in a flow to make sure they are functioning properly and handling problems the way they should.

    • End-to-end testing − From input to output, end-to-end testing examines the full flow of a whole system. Tools like Selenium, which can mimic user interactions with the flow and test error-handling skills, can be used for this.

5. Node-RED Contrib Modules

  • More nodes and functionalities for managing failures are offered by Node-RED Contrib modules. When you need to watch the data flow in real-time, for instance, the Debug Overlay node might be handy since it immediately shows debug information on the screen.

  • Any Node-RED flow must be able to handle errors, and there are various Node-RED Contrib modules that can do this.

    • The "try-catch" node provided by the node-red-contrib-trycatch module may be used to detect mistakes in a flow and gracefully manage them. The node has the option of configuring the error message to be sent to a different flow for additional processing.

    • Errors in a flow can be caught and handled using the "catch" node provided by the node-red-contrib-error-handler module. The node can be set up to report the error message to a file, the transfer failed messages to a different flow for additional processing, or retry unsuccessful messages.

    • The "catch" node provided by the node-red-contrib-catch module may be used to detect mistakes in a flow and gracefully manage them. The node can be set up to report the error message to a file or transfer it to a different flow for additional processing.


You may successfully handle failures in Node-RED and build stronger, more dependable workflows by adhering to the recommended practices described in this article. Always keep an eye on your flows, employ the right error-handling nodes, and use error avoidance best practices. You may lessen the effects of mistakes and maintain the smooth flow of your data by using these tools and strategies.

Updated on: 13-Apr-2023


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