Error Handling
Last updated
Last updated
Workflow applications often comprise multiple interconnected nodes operating in sequence. When an error occurs—such as an API request failure, an LLM output issue, or an unexpected exception—it can disrupt the entire process. Such disruptions force developers to spend significant time troubleshooting, especially in workflows with complex node dependencies.
Error handling introduces robust strategies to manage node failures effectively. These feature allow workflows to log and monitor errors without halting execution or switch seamlessly to predefined fallback paths, ensuring task continuity. Developers can significantly improve application reliability and operational resilience by integrating strong error-handling feature into critical nodes.
Developers no longer need to handle potential node errors by embedding complex logic within nodes or adding extra nodes. The error-handling feature simplifies workflow design, enabling streamlined execution through various predefined strategies.
Example: In a workflow that retrieves and aggregates data from three API services (such as weather services, news summaries, and social media analysis), one service might fail to respond due to request limits, causing data retrieval to fail. With the error-handling function, the main process can continue using the data from the other two successful services while logging the failed API request. This log helps developers analyze the issue later and refine their service call strategies.
Example: An LLM node tasked with generating detailed document summaries may encounter token limit errors when processing lengthy input. The workflow can switch to a backup path by setting the "Fail branch" on Error-handling Feature.
For instance, a code node on the alternative path can split the content into smaller chunks and re-invoke the LLM node, preventing the workflow from breaking down.
Example: When running a workflow, you might occasionally encounter a node returning vague error messages (such as a simple "request failed"), complicating pinpointing the issue quickly. Developers can write predefined error messages within the error handling feature to provide more explicit and more precise error information for subsequent application debugging.
The following four types of nodes have added error-handling feature. Click on the title to read the detailed documents:
The error handling feature provides the following three options:
• None: Do not handle the exception, directly throw the node's error message and interrupt the entire process.
• Default Value: Allows developers to predefine exception messages. After an exception occurs, use the predefined value to replace the original built-in error output message of the node.
• Fail Branch: Execute the pre-arranged fail branch after an exception occurs.
For explanations and configuration methods of each strategy, please refer to the predefined error handling logic.
Scenario: Enabling Error-handling feature for Workflow Application
Error Handling feature for Code Output in Workflow Applications The following example demonstrates how to implement error handling feature within a workflow application, using fail branch to handle node exceptions.
The idea of the workflow design: An LLM node generates JSON code content (either correctly or incorrectly formatted) based on user's input instructions, which is then executed and output through Code Node A.
If Code Node A receives incorrectly formatted JSON content, it follows the predefined error handling design, executing the backup path while continuing the main process.
Creating a JSON Code Generation Node
Create a new Workflow application and add both LLM and Code nodes. Use a Prompt to instruct the LLM to generate either correctly or incorrectly formatted JSON content, which will then be validated through Code Node A.
The Prompt reference of LLM node:
The JSON verification of Code Node：
Enable Error Handling Feature for Node A
Node A is responsible for validating JSON content. If it receives incorrectly formatted JSON content, the error handling feature will be triggered and execute th backup path, allowing the subsequent LLM node to fix the incorrect content and revalidate the JSON, thereby continuing the main process.
In the "Error Handling" tab of Node A, select "Fail Branch" and create a new LLM node.
Correct the Error Output from Node A
In the new LLM node, fill in the prompt and reference the exception output from Node A using variables for correction. Add Node B to revalidate the JSON content.
4. End
Add a variable aggregation node to consolidate the results from both the correct and error branches and output them to the end node, completing the entire process.
Click here to download the Demo DSL file.
In workflow applications, understanding both node and workflow status is crucial for effective monitoring and troubleshooting. Let's explore how status indicators help developers track execution progress and handle exceptions efficiently.
Success: Every node runs properly - the node completes its task and produces the expected output.
Failure: When error handling isn't enabled, the node stops working and reports an error.
Exception: Even though an error occurs, the node doesn't completely fail because error handling (either default values or alternative paths) kicks in to manage the situation.
Success: A perfect run - all nodes complete their tasks successfully, and the workflow produces the intended output.
Failure: The workflow stops completely due to an unhandled node error.
Partial Success: Think of this as a "managed failure" - while some nodes encounter issues, error handling mechanisms keep the workflow moving forward to completion.
What is the difference before and after enabling the exception handling mechanism?
Without error handling, workflows are quite fragile:
A single node failure (like an LLM timeout or network hiccup) brings everything to a halt
Developers must manually investigate and fix issues before restarting
Creating workarounds means building complex, redundant safety nets
Error messages tend to be vague and unhelpful
Error handling transforms your workflow into a more resilient system:
Workflows keep running even when things go wrong
Developers can create custom responses for different types of errors
The overall design becomes cleaner and more maintainable
Detailed error logging makes troubleshooting much faster
How to debug the execution of backup paths?
Need to check if your error handling is working? It's simple - just look for yellow-highlighted paths in your workflow logs. These visual indicators show exactly when and where your backup error handling routes are being used.
