fix(core): Improve model sub-nodes error handling #11418
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One thing I noticed, that's a difference now is that I don't really get a sense for what's wrong with my credential, whereas on master I do: 
Now it just says something is wrong with my credentials: 
Why did that change? I think getting the things to check directly in the toast is a better experience. |
I don't know why, but now I cannot reproduce this anymore. |
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On line 326 is another occurrence of context.functionality -- can you check if that needs to change too?
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And same for packages/editor-ui/src/utils/expressions.ts line 63.
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Should be fine as this is for another case, when nodes use "pairedItem" feature (e.g. referencing previous node's item value when the pairedItem connection was interrupted)
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but you don't set context.functionality anymore now? does that functionality break?
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It's being set in n8nLlmFailedAttemptHandler.ts when we wrap the error into NodeApiError. For the paired item exceptions – nothing changes, I guess it's being set in WorkflowDataProxy.ts and should not be affected by this PR.
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Ahh, I see your point now. I found that setting context.functionality to configuration-node on NodeApiError does nothing, as it checks for the functionality on the exception object itself. Now I see that the checks are different for the configuration-node functionality and pairedItem. Good catch, thank you!
…in-the-sub-node-even-if # Conflicts: # packages/@n8n/nodes-langchain/nodes/llms/N8nLlmTracing.ts
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| Run duration | 04m 22s |
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| Committer | Eugene Molodkin |
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✅ All Cypress E2E specs passed |
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Summary
Problem
The current error handling in LLM sub-nodes has two main issues:
Context
The error handling relies on custom exception classes (e.g.,
NodeOperationError). However, there's no straightforward mechanism to wrap model exceptions before they propagate to the root node.Solution Approaches Explored
N8nLlmTracing(callback handler passed to the LangChain model's contructor). UsinghandleLLMErrorcallback handler allows to add proper error info to the sub-node and fix the infinite running issue. But it can not be used for wrapping the exception for the root node.onFailedAttemptcallback can be provided during each model's LangChain class instantiation. It allows to intercept the retry logic built into LangChain, and re-throw the wrapped exceptions.Implementation
To use the second approach, the new helper function
makeN8nLlmFailedAttemptHandlerwas implemented. It catches LLM errors, wrap them with our custom error classes, provides some default error handling logic (interrupt running if it does not make sense to retry for the specific error), and also allows to customize error handling for the specific cases (for example to use a custom error message for the OpenAI's insufficient quota error).Known issues
Couple of LangChain model classes do not use the
AsyncCallerfor their calls. It means, that the common retry logic built into LangChain does not work in such cases. TheonFailedAttemptcallback is not being called as well.Thus, the described error wrapping logic does not work yet for the following models:
LMChatOllamaLmChatAwsBedrockLmChatGoogleVertexExample 1. Insufficient quota error (OpenAI)
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Example 2. Empty prompt (Anthropic)
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Example 3. Nested sub-node error
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Example 4. Nested sub-node error
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After:
Related Linear tickets, Github issues, and Community forum posts
Review / Merge checklist
release/backport(if the PR is an urgent fix that needs to be backported)