Amazon CodeCatalyst is no longer open to new customers. Existing customers can continue to use the service as normal. For more information, see [How to migrate from CodeCatalyst](migration.md).
# Gating a workflow run
A *gate* is a workflow component that you can use to prevent a workflow run from proceeding unless certain conditions are met. An example of a gate is the **Approval** gate where users must submit an approval in the CodeCatalyst console before the workflow run is allowed to continue.
You can add gates between sequences of actions in a workflow, or before the first action (which runs immediately after the **Source** downloads). You can also add gates after the last action, if you have a need to do so.
For more information about workflow runs, see [Running a workflow](workflows-working-runs.md).
**Topics**
+ [Gate types](#workflows-gates-types)
+ [Can I set up a gate to run in parallel to another action?](#workflows-approval-parallel)
+ [Can I use a gate to prevent a workflow run from starting?](#workflows-gates-prevent)
+ [Limitations of gates](#workflows-gate-limitations)
+ [Adding a gate to a workflow](workflows-gates-add.md)
+ [Sequencing gates and actions](workflows-gates-depends-on.md)
+ [Specifying the version of a gate](workflows-gates-version.md)
## Gate types
Currently, Amazon CodeCatalyst supports one type of gate: the **Approval** gate. For more information, see [Requiring approvals on workflow runs](workflows-approval.md).
## Can I set up a gate to run in parallel to another action?
No. Gates can only run before or after an action. For more information, see [Sequencing gates and actions](workflows-gates-depends-on.md).
## Can I use a gate to prevent a workflow run from starting?
Yes, with qualifications.
You can prevent a workflow run from *performing tasks*, which is slightly different from preventing it from *starting*.
To prevent a workflow from performing tasks, add a gate before the very first action in a workflow. In this scenario, a workflow run *will start*—meaning it will download your source repository files—but it will be prevented from performing tasks until the gate is unlocked.
**Note**
Workflows that start and then get blocked by a gate still count against your *Maximum number of concurrent workflow runs per space* quota and other quotas. To ensure that you do not exceed workflow quotas, consider using a workflow trigger to conditionally start a workflow instead of using a gate. Also consider using a pull request approval rule instead of a gate. For more information about quotas, triggers, and pull request approval rules, see [Quotas for workflows in CodeCatalyst](workflows-quotas.md), [Starting a workflow run automatically using triggers](workflows-add-trigger.md), and [Managing requirements for merging a pull request with approval rules](source-pull-requests-approval-rules.md).
## Limitations of gates
Gates have the following limitations:
+ Gates cannot be used in conjunction with the compute sharing feature. For more information about this feature, see [Sharing compute across actions](compute-sharing.md).
+ Gates cannot be used within action groups. For more information about action groups, see [Grouping actions into action groups](workflows-group-actions.md).
# Adding a gate to a workflow
In Amazon CodeCatalyst, you can add a gate to a workflow to prevent it from proceeding unless certain conditions are met. Use the following instructions to add a gate to a workflow.
For more information about gates, see [Gating a workflow run](workflows-gates.md).
**To add and configure a gate**
1. Open the CodeCatalyst console at [https://codecatalyst.aws/](https://codecatalyst.aws/).
1. Choose your project.
1. In the navigation pane, choose **CI/CD**, and then choose **Workflows**.
1. Choose the name of your workflow. You can filter by the source repository or branch name where the workflow is defined, or filter by workflow name or status.
1. Choose **Edit**.
1. Choose **Visual**.
1. On the left, choose **Gates**.
1. In the gate catalog, search for a gate, and then choose the plus sign (**\$1**) to add the gate to your workflow.
1. Configure the gate. Choose **Visual** to use the visual editor, or **YAML** to use the YAML editor. For detailed instructions, see:
+ [Adding an 'Approval' gate](workflows-approval-add.md)
1. (Optional) Choose **Validate** to make sure the YAML code is valid.
1. Choose **Commit** to commit your changes.
# Sequencing gates and actions
In Amazon CodeCatalyst, you can set up a gate to run before or after a workflow action, action group, or gate. For example, you might set up an `Approval` gate to run before a `Deploy` action. In this case, the `Deploy` action is said to *depend on* the `Approval` gate.
To set up dependencies between gates and actions, configure the gate or action's **Depends on** property. For instructions, see [Setting up dependencies between actions](workflows-depends-on-set-up.md). The referenced instructions refer to workflow *actions* but apply equally to gates.
For an example of how to set up the **Depends on** property with a gate, see [Example: An 'Approval' gate](workflows-approval-example.md).
For more information about gates, see [Gating a workflow run](workflows-gates.md).
For more information about workflow actions, see [Configuring workflow actions](workflows-actions.md).
# Specifying the version of a gate
By default, when you add a gate to a workflow, CodeCatalyst adds the full version to the workflow definition file using the format:
`vmajor.minor.patch`
For example:
```
My-Gate:
Identifier: aws/approval@v1
```
You can lengthen the version so that the workflow uses a specific major or minor version of the gate. For instructions, see [Specifying the action version to use](workflows-action-versions.md). The referenced topic refers to workflow actions but applies equally to gates.
For more information about gates in CodeCatalyst, see [Gating a workflow run](workflows-gates.md).