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n8n - 💡(How to fix) Fix Wait node breaks concurrency=1 in queue mode [3 comments, 3 participants]

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n8n-io/n8n#28488•Fetched 2026-04-15 06:44:18
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Comments
3
Participants
3
Timeline
8
Reactions
0
Author
Atahan-TurkogluAtahan-Turkoglu
Participants
Atahan-TurkogluAtahan-TurkogluDeroswentDeroswentn8n-assistant[bot]n8n-assistant[bot]
Timeline (top)
commented ×3subscribed ×2cross-referenced ×1labeled ×1

Error Message

  • error: all

Fix Action

Fix / Workaround

In queue mode with worker --concurrency=1, the Wait node releases the worker slot when reached, allowing multiple executions to run simultaneously. This behavior breaks the concurrency=1 constraint. The issue occurs regardless of whether the Wait node is at the end or in the middle of the workflow. Workaround: Using a Code node with setTimeout() instead of the Wait node respects concurrency=1 correctly. Note: Debug info reports concurrency: -1 despite worker running with --concurrency=1 flag.

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Bug Description

In queue mode with worker --concurrency=1, the Wait node releases the worker slot when reached, allowing multiple executions to run simultaneously. This behavior breaks the concurrency=1 constraint. The issue occurs regardless of whether the Wait node is at the end or in the middle of the workflow. Workaround: Using a Code node with setTimeout() instead of the Wait node respects concurrency=1 correctly. Note: Debug info reports concurrency: -1 despite worker running with --concurrency=1 flag.

To Reproduce

  1. Set up queue mode with worker --concurrency=1
  2. Create workflow: Schedule Trigger (5s) → Wait node (10s)
  3. Publish and observe executions
  4. Multiple executions run simultaneously instead of waiting

Expected behavior

Only 1 execution at a time

Debug Info

Debug info

core

  • n8nVersion: 2.16.0
  • platform: docker (self-hosted)
  • nodeJsVersion: 24.14.1
  • nodeEnv: production
  • database: postgres
  • executionMode: scaling (single-main)
  • concurrency: -1
  • license: enterprise (production)
  • consumerId: 5cc0e17f-6946-4439-bbbd-cca15bd9b2a1

storage

  • success: none
  • error: all
  • progress: false
  • manual: false
  • binaryMode: database

pruning

  • enabled: true
  • maxAge: 2400 hours
  • maxCount: 10000 executions

client

  • userAgent: mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/147.0.0.0 safari/537.36
  • isTouchDevice: false

Generated at: 2026-04-14T15:12:54.265Z

Operating System

Windows 11 Pro (25H2)

n8n Version

2.16.0

Node.js Version

24.14.1

Database

PostgreSQL

Execution mode

queue

Hosting

self hosted

extent analysis

TL;DR

Using a Code node with setTimeout() instead of the Wait node may help respect the concurrency=1 constraint in queue mode.

Guidance

  • The issue seems to be related to the Wait node releasing the worker slot, allowing multiple executions to run simultaneously, which breaks the concurrency=1 constraint.
  • To verify the issue, set up a workflow with a Schedule Trigger and a Wait node, and observe if multiple executions run simultaneously.
  • As a potential workaround, try replacing the Wait node with a Code node that uses setTimeout() to pause the execution, as this has been reported to respect the concurrency=1 constraint correctly.
  • Check the debug info to ensure that the worker is running with the --concurrency=1 flag, despite the reported concurrency: -1.

Example

// Example Code node with setTimeout()
async function pauseExecution(timeout) {
  await new Promise(resolve => setTimeout(resolve, timeout));
}

Note: This example is based on the provided workaround and may need to be adapted to the specific use case.

Notes

The root cause of the issue is not explicitly stated, but it seems to be related to the Wait node's behavior in queue mode. The provided workaround may help mitigate the issue, but further investigation may be needed to determine the underlying cause.

Recommendation

Apply the workaround by using a Code node with setTimeout() instead of the Wait node, as this has been reported to respect the concurrency=1 constraint correctly.

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FAQ

Expected behavior

Only 1 execution at a time

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