Skip to main content

Concurrency

Concurrency control prevents multiple workflow instances from running simultaneously. Use this feature to protect shared resources and prevent conflicts.

Fields​

group (required)​

Concurrency group identifier. Workflows with the same group cannot run concurrently.

Type: string (non-empty)

Supports expressions: Yes

Example:

concurrency:
  group: production-deploy

With expressions:

concurrency:
  group: train-${{ .inputs.model_type }}

cancel_in_progress (optional)​

Controls behavior when a new workflow arrives while another is running in the same group.

Type: bool

Default: false

ValueBehavior
trueCancel the running workflow and start the new one immediately
falseQueue the new workflow (maximum 1 running + 1 pending; newer replaces pending)

Example:

concurrency:
  group: model-training
  cancel_in_progress: true

Behavior​

Queue mode (cancel_in_progress: false)​

  • Maximum: 1 running + 1 pending workflow
  • New arrivals replace the pending workflow (keeps newest)
  • When the running workflow completes, the pending one starts

Cancel mode (cancel_in_progress: true)​

  • New workflow cancels the running workflow
  • No queue: the newest workflow always runs

Examples​

Model deployment​

Ensure only one model deployment runs at a time:

id: deploy-model

concurrency:
  group: production-deploy

jobs:
  deploy:
    steps:
      - run: python deploy_model.py --env production

Per-model training​

Allow concurrent training of different models, but serialize same-model training:

id: train-model

inputs:
  model_type:
    type: string
    required: true

concurrency:
  group: train-${{ .inputs.model_type }}

jobs:
  train:
    steps:
      - run: python train.py --model ${{ .inputs.model_type }}

Experiment with cancel​

For experiments where only the latest hyperparameters matter:

id: hyperparameter-tuning

inputs:
  experiment_id:
    type: string

concurrency:
  group: experiment-${{ .inputs.experiment_id }}
  cancel_in_progress: true

jobs:
  tune:
    steps:
      - run: python tune.py --experiment ${{ .inputs.experiment_id }}

Interaction with other features​

cancel_on_failure​

Concurrency cancellations have state cancelled (not failed), so they don't trigger cancel_on_failure in other workflows.

Expressions​

Concurrency groups support the same expression contexts as other fields: .inputs, .secrets, and .env.

Feedback