An error occurred when calling the workflow API: {“code”: “internal_server_error”, “message”: “The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.”, “status”: 500}. The concurrency level is 3. How should this be resolved?
Thank you for the detail. Regarding the concurrency setting, the value of 3 is mainly used as a request-level limit and doesn’t necessarily reflect the overall capacity of workflow execution.
When a workflow includes an Iteration / Loop node, a single request may internally trigger multiple executions, such as LLM calls, tool or plugin invocations, and database operations. In these cases, the effective load can increase quickly, and this may lead to a 500 error if one of the underlying components is under pressure.
Have you already solve this issue?
If not, a few things that often help are:
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Temporarily lowering concurrency to 1–2, especially for workflows with loops
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Reducing the workload inside the Iteration node (for example, batch size or heavy LLM/tool calls)
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Checking server logs for database connection or plugin-related warnings
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If this is on Dify Cloud, sharing the request time and workflow ID can help with further investigation
Please let us know whether the issue persists after these adjustments, and we’ll be happy to help look into it further.