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dify - ✅(Solved) Fix Improve default GraphEngine worker count for small parallel workflows [1 pull requests, 1 participants]

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langgenius/dify#35561•Fetched 2026-04-26 05:24:41
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Root Cause

Proposal: Change the default value to:

GRAPH_ENGINE_MIN_WORKERS=3

Why this helps: Gives common 2-3 branch workflows enough baseline workers. Makes the canvas behavior closer to runtime behavior. Reduces the need for users to tune hidden environment variables. Keeps the change conservative because GRAPH_ENGINE_MAX_WORKERS and scale-up behavior stay unchanged.

Fix Action

Fixed

PR fix notes

PR #35562: chore: increase default graph engine min workers

Description (problem / solution / changelog)

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Summary

Fixes #35561 This PR changes the default GRAPH_ENGINE_MIN_WORKERS from 1 to 3.

Why:

The previous default starts each GraphEngine run with only one worker. This can make common workflows with 2 or 3 independent parallel branches run mostly sequentially unless users manually tune the environment variable.

Using 3 as the default gives small parallel workflows enough baseline workers while keeping the change conservative.

Changes:

  • Set default GRAPH_ENGINE_MIN_WORKERS to 3
  • Keep GRAPH_ENGINE_MAX_WORKERS unchanged
  • Keep GRAPH_ENGINE_SCALE_UP_THRESHOLD unchanged

Impact:

  • Better out-of-box behavior for small parallel workflows
  • Slightly higher baseline thread usage per workflow run
  • Existing deployments can still override the value with environment variables
<!-- Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change. --> <!-- If this PR was created by an automated agent, add `From <Tool Name>` as the final line of the description. Example: `From Codex`. -->

Screenshots

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Checklist

  • This change requires a documentation update, included: Dify Document
  • I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
  • I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
  • I've updated the documentation accordingly.
  • I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

Changed files

  • api/.env.example (modified, +2/-2)
  • api/configs/feature/__init__.py (modified, +1/-1)
  • api/tests/unit_tests/core/workflow/graph_engine/test_table_runner.py (modified, +2/-2)
  • docker/.env.example (modified, +2/-2)
  • docker/docker-compose.yaml (modified, +1/-1)

Code Example

GRAPH_ENGINE_MIN_WORKERS=1

---

GRAPH_ENGINE_MIN_WORKERS=3
RAW_BUFFERClick to expand / collapse

Self Checks

  • I have read the Contributing Guide and Language Policy.
  • I have searched for existing issues search for existing issues, including closed ones.
  • I confirm that I am using English to submit this report, otherwise it will be closed.
  • Please do not modify this template :) and fill in all the required fields.

1. Is this request related to a challenge you're experiencing? Tell me about your story.

Dify supports parallel branches in workflows, but the current default GraphEngine worker count can make small parallel workflows look sequential.

Current default:

GRAPH_ENGINE_MIN_WORKERS=1

With only one initial graph worker, workflows with 2 or 3 independent parallel nodes may not start those nodes at the same time. Users then need to discover and tune GRAPH_ENGINE_MIN_WORKERS manually, even for common parallel workflow patterns.

This has caused confusion in several reports where users expected parallel branches to run concurrently but observed sequential execution.

Related reports:

#26565 #29208 #29450 #31054 #31196 #34222

Proposal: Change the default value to:

GRAPH_ENGINE_MIN_WORKERS=3

Why this helps: Gives common 2-3 branch workflows enough baseline workers. Makes the canvas behavior closer to runtime behavior. Reduces the need for users to tune hidden environment variables. Keeps the change conservative because GRAPH_ENGINE_MAX_WORKERS and scale-up behavior stay unchanged.

Scope: This only improves parallel node execution inside a single GraphEngine run.

2. Additional context or comments

No response

3. Can you help us with this feature?

  • I am interested in contributing to this feature.

extent analysis

TL;DR

Increase the default GRAPH_ENGINE_MIN_WORKERS value to improve parallel workflow execution in Dify.

Guidance

  • Review the current GRAPH_ENGINE_MIN_WORKERS setting and consider increasing it to 3 to support common parallel workflow patterns.
  • Verify the impact of this change by testing workflows with 2-3 independent parallel nodes and observing their execution order.
  • Check related reports (#26565, #29208, #29450, #31054, #31196, #34222) for similar issues and potential feedback on this proposed solution.
  • Consider the scope of this change, which only affects parallel node execution inside a single GraphEngine run.

Example

GRAPH_ENGINE_MIN_WORKERS=3

This example shows the proposed new default value for GRAPH_ENGINE_MIN_WORKERS.

Notes

This solution assumes that increasing the minimum worker count will not introduce significant performance issues or other unintended consequences.

Recommendation

Apply workaround: Increase the default GRAPH_ENGINE_MIN_WORKERS value to 3, as it is a conservative change that addresses common parallel workflow patterns and reduces the need for manual tuning.

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