Continuous Delivery

Skaffold provides several features and sub-command “building blocks” that make it very useful for integrating with (or creating entirely new) CI/CD pipelines. The ability to use the same skaffold.yaml for iterative development and continuous delivery eases handing off an application from a development team to an ops team.

Let’s start with the simplest use case: a single, full deployment of your application.

Run entire pipeline end-to-end

skaffold run is a single command for a one-off deployment. It runs through every major phase of the Skaffold lifecycle: building your application images, tagging these images (and optionally pushing them to a remote registry), deploying your application to the target cluster, and monitoring the created resources for readiness.

We recommend skaffold run for the simplest Continuous Delivery setup, where it is sufficient to have a single step that deploys from version control to a cluster.

For more sophisticated Continuous Delivery pipelines, Skaffold offers building blocks:

• status-check - wait for deployments to stabilize and succeed only if all deployments are successful
• skaffold build - build, tag and push artifacts to a registry
• skaffold deploy - deploy built artifacts to a cluster
• skaffold render - export the transformed Kubernetes manifests
• skaffold apply - send hydrated Kubernetes manifests to the API server to create resources on the target cluster

Traditional continuous delivery

skaffold build will build your project’s artifacts, and push the build images to the specified registry. If your project is already configured to run with Skaffold, skaffold build can be a very lightweight way of setting up builds for your CI pipeline. Passing the --file-output flag to Skaffold build will also write out your built artifacts in JSON format to a file on disk, which can then by passed to skaffold deploy later on. This is a great way of “committing” your artifacts when they have reached a state that you’re comfortable with, especially for projects with multiple artifacts for multiple services.

Example using the current git state as a unique file ID to “commit” build state:

Storing the build result in a commit specific JSON file:

export STATE=$(git rev-list -1 HEAD --abbrev-commit)
skaffold build --file-output build-$STATE.json

outputs the tag generation and cache output from Skaffold:

Generating tags...
 - gcr.io/k8s-skaffold/skaffold-example:v0.41.0-17-g3ad238db
Checking cache...
 - gcr.io/k8s-skaffold/skaffold-example: Found. Tagging

The content of the JSON file

cat build-$STATE.json

looks like:

{"builds":[{"imageName":"gcr.io/k8s-skaffold/skaffold-example","tag":"gcr.io/k8s-skaffold/skaffold-example:v0.41.0-17-g3ad238db@sha256:eeffb639f53368c4039b02a4d337bde44e3acc728b309a84353d4857ee95c369"}]}

We can then use this build result file to deploy with Skaffold:

skaffold deploy -a build-$STATE.json

and as we’d expect, we see a bit of deploy-related output from Skaffold:

Tags used in deployment:
 - gcr.io/k8s-skaffold/skaffold-example -> gcr.io/k8s-skaffold/skaffold-example:v0.41.0-17-g3ad238db@sha256:eeffb639f53368c4039b02a4d337bde44e3acc728b309a84353d4857ee95c369
Starting deploy...
 - pod/getting-started configured

Separation of rendering and deployment

Skaffold allows separating the generation of fully-hydrated Kubernetes manifests from the actual deployment of those manifests, using the skaffold render and skaffold apply commands.

skaffold render builds all application images from your artifacts, templates the newly-generated image tags into your Kubernetes manifests (based on your project’s deployment configuration), and then prints out the final hydrated manifests to a file or your terminal. This allows you to capture the full, declarative state of your application in configuration, such that applying the changes to your cluster can be done as a separate step.

skaffold apply consumes one or more fully-hydrated Kubernetes manifests, and then sends the results directly to the Kubernetes control plane via kubectl to create resources on the target cluster. After creating the resources on your cluster, skaffold apply uses Skaffold’s built-in health checking to monitor the created resources for readiness. See resource health checks for more information on how Skaffold’s resource health checking works.

Note: skaffold apply always uses kubectl to deploy resources to a target cluster, regardless of deployment configuration in the provided skaffold.yaml. Only a small subset of deploy configuration is honored when running skaffold apply:

• deploy.statusCheckDeadlineSeconds
• deploy.kubeContext
• deploy.logs.prefix
• deploy.kubectl.flags
• deploy.kubectl.defaultNamespace
• deploy.kustomize.flags
• deploy.kustomize.defaultNamespace

skaffold apply works with any arbitrary Kubernetes YAML, whether it was generated by Skaffold or not, making it an ideal counterpart to skaffold render.

GitOps-style continuous delivery

You can use this separation of rendering and deploying to enable GitOps CD pipelines.

GitOps-based CD pipelines traditionally see fully-hydrated Kubernetes manifests committed to a configuration Git repository (separate from the application source), which triggers a deployment pipeline that applies the changes to resources on the cluster.

Example: Hydrate manifests then deploy/apply to cluster

First, use skaffold render to hydrate the Kubernetes resource file with a newly-built image tag:

$ skaffold render --output render.yaml

# render.yaml
apiVersion: v1
kind: Pod
metadata:
  name: getting-started
  namespace: default
spec:
  containers:
  - image: gcr.io/k8s-skaffold/skaffold-example:v1.19.0-89-gdbedd2a20-dirty
    name: getting-started

Then, we can apply this output directly to the cluster:

$ skaffold apply render.yaml

Starting deploy...
 - pod/getting-started created
Waiting for deployments to stabilize...
Deployments stabilized in 49.277055ms