locks.md

Deployment Locks and Actions Concurrency 🔓

Only run one deployment at a time

There are multiple ways to leverage this action for deployment locks! Let's take a look at each option

Deployment Locks

The suggested way to go about deployment locking is to use the built in locking feature in this Action!

Just like how you can comment .deploy on a pull request to trigger a deployment, you can also comment .lock to lock deployments. This will prevent other users from triggering a deployment. The lock is associated with your GitHub handle, so you will be able to deploy any pull request in the repository and as many times as you want. Any other user who attempts a deployment while your lock is active will get a comment on their PR telling them that a lock is in effect.

To release the deployment lock, simply comment .unlock on any pull request in the repository at anytime. Please be aware that other users can run this same command to remove the lock (in case you get offline and forget to do so 😉)

These deployment locks come in two flavors:

• sticky
• non-sticky

sticky locks are locks that persist until you remove them. As seen in the example above, the .lock command creates a sticky lock that will persist until someone runs .unlock

non-sticky locks are temporary locks that only exist during a deployment. This action will automatically create a non-sticky lock for you when you run .deploy. It does this to prevent another user from running .deploy in another pull request and creating a deployment conflict

Deployment locks in relation to environments also come in two flavors:

• environment specific
• global

environment specific locks are locks that are associated with a specific environment. This means that if you have two environments, staging and production, you can have a lock on staging and another lock on production at the same time. These locks are independent of each other and will not prevent you from deploying to the other environment if another user has a lock in effect.

global locks are locks that are associated with the entire project/repository. This means that if you have two environments, staging and production, you can have a lock on the entire repository and prevent any deployments to either environment.

Deployment Lock Core Concepts

Let's review the core concepts of deployment locks in a short summary:

• Deployment locks are used to prevent multiple deployments from running at the same time and breaking things
• Non-sticky locks are created automatically when running .deploy or .noop
• Sticky locks are created manually by commenting .lock on a pull request - They will persist until you remove them with .unlock
• Locks are associated to a user's GitHub handle - This user can deploy any pull request in the repository and as many times as they want
• Any user can remove a lock by commenting .unlock on any pull request in the repository
• Details about a lock can be viewed with .lock --details
• Locks can either be environment specific or global
• Like all the features of this Action, users need write permissions or higher to use a command

How do Deployment Locks Work?

This Action uses GitHub branches to create a deployment lock. When you run .lock the following happens:

1. The Action checks to see if a global lock already exists, if it doesn't it will then check to see if an environment specific lock exists
2. If a lock does not exists it begins to create one for you
3. The Action creates a new branch called <environment|global>-branch-deploy-lock
4. The Action then creates a lock file called lock.json on the new branch
5. The lock.json file contains metadata about the lock

Now when new deployments are run, they will check if a lock exists. If it does and it doesn't belong to you, your deployment is rejected. If the lock does belong to you, then the deployment will continue.

Deployment Lock Examples 📸

Here are a few examples of deployment locks in action!

Lock Example:

Unlock Example:

Locking a specific environment (not just the default one):

Obtaining the lock details for development:

Remove the lock for development:

Creating a global deploy lock:

Removing the global deploy lock:

Actions Concurrency

Note: Using the locking mechanism included in this Action (above) is highly recommended over Actions concurrency. The section below will be included anyways should you have a valid reason to use it instead of the deploy lock features this Action provides

If your workflows need some level of concurrency or locking, you can leverage the native GitHub Actions concurrency feature (documentation) to enable this.

For example, if you have two users run .deploy on two separate PRs at the same time, it will trigger two deployments. In some cases, this will break things and you may not want this. By using Actions concurrency, you can prevent multiple workflows from running at once

The default behavior for Actions is to run the first job that was triggered and to set the other one as pending. If you want to cancel the other job, that can be configured as well. Below you will see an example where we setup a concurrency group which only allows one deployment at a time and cancels all other workflows triggered while our deployment is running:

concurrency: 
  group: production
  cancel-in-progress: true

Need More Deployment Lock Control?

If you need more control over when, how, and why deployment locks are set, you can use the github/lock Action!

This Action allows you to set a lock via an issue comment, custom condition, on merges, etc. You have full control over when and how the lock is set and removed!