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Concurrency control#

In regular mode, n8n doesn't limit how many production executions may run at the same time. This can lead to a scenario where too many concurrent executions thrash the event loop, causing performance degradation and unresponsiveness.

To prevent this, you can set a concurrency limit for production executions in regular mode. Use this to control how many production executions run concurrently, and queue up any concurrent production executions over the limit. These executions remain in the queue until concurrency capacity frees up, and are then processed in FIFO order.

Concurrency control is disabled by default. To enable it:


Keep in mind:

  • Concurrency control applies only to production executions: those started from a webhook or trigger node. It doesn't apply to any other kinds, such as manual executions, sub-workflow executions, error executions, or started from CLI.
  • You can't retry queued executions. Cancelling or deleting a queued execution also removes it from the queue.
  • On instance startup, n8n resumes queued executions up to the concurrency limit and re-enqueues the rest.
  • To monitor concurrency control, watch logs for executions being added to the queue and released. In a future version, n8n will show concurrency control in the UI.

Comparison to scaling mode#

In scaling mode, you can control how many jobs a worker may run concurrently using the --concurrency flag.

Concurrency control in scaling mode is a separate mechanism from concurrency control in regular mode, but the environment variable N8N_CONCURRENCY_PRODUCTION_LIMIT controls both of them. In scaling mode, n8n takes the limit from this variable if set to a value other than -1, falling back to the --concurrency flag or its default.