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Getting ready to deploy your Appsody project

When you've finished the development work for your Appsody project, you will have a containerized application that's ready to deploy to a suitable runtime infrastructure such as a cloud platform that hosts a Kubernetes cluster.

The Appsody CLI provides the appsody deploy command to build and deploy a Docker image directly to a Kubernetes cluster that you are using for testing or staging.

You can delegate the build and deployment steps to an external pipeline, such as a Tekton pipeline that consumes the source code of your Appsody project after you push it to a GitHub repository. Within the pipeline, you can run appsody build, which builds the application image and generates a deployment manifest. You can use the manifest to deploy your application to a Kubernetes environment where the Appsody operator is installed.

These deployment options are covered in more detail in the following sections.

Deploying your app directly to a Kubernetes cluster

There are many options to deploy your Appsody applications to a Kubernetes cluster. The best approach depends on the specific scenario:

  • If you are testing your app on a locally installed cluster, using appsody deploy is your best bet
  • If you intend to have your app deployed on a shared cluster for integration testing or production, you are probably going to rely on CI/CD pipelines, and have the app built and deployed from its source.

The appsody deploy command provides a way for you to deploy your application directly to a Kubernetes cluster. The stack contains a deployment manifest that can be consumed by the Appsody operator. appsody deploy will install the operator, if necessary, and deploy your application to the cluster using that deployment manifest.

If you want to deploy your application without rebuilding the application image, or modifying the deployment manifest, you can run

appsody deploy --no-build

Deployment via the Appsody Operator

Kubernetes operators offer a powerful way to provide full lifecycle maintenance of a wide range of resources on Kubernetes clusters. In particular, they can install, upgrade, remove, and monitor application deployments. The recently published Appsody operator automates the installation and maintenance of a special type of Custom Resource Definitions (CRDs), called AppsodyApplication.

The Appsody stacks that are currently available include a template of such a CRD manifest. When you run appsody deploy on a project created from one of the stacks enabled with those manifests, the CLI customizes the manifest with information that is specific to the deployment (such as namespace and project name), and submits the manifest to the Appsody operator on the Kubernetes cluster.

In fact, if your cluster does not already provide an operator, appsody deploy will install one for you. You can also use the Appsody CLI to install an instance of the Appsody operator, without installing any applications. This can be achieved by running the appsody operator install command.

To find out more about the Appsody operator, see here.

Deployment as a Knative Service

You can deploy your application as a Knative service on your target Kubernetes cluster by using the --knative flag with the appsody build or appsody deploy commands. This action sets the flag createKnativeService in the deployment manifest to true.

For your app to work as a Knative service, the following pre-requisites apply:

  • You must have access to a Kubernetes cluster, with Knative Serving installed and running. To install Knative locally, use the Kubernetes feature in Docker for Desktop, see Installing Knative Locally. To install Knative on other Kubernetes clusters, see the Knative Install Documentation.
  • You must configure your kubectl CLI to point to your Kubernetes cluster.
  • If you intend to push the Docker image containing your application to Docker Hub, your target cluster must be configured to pull images from Docker Hub.

Once the appsody deploy --knative command completes successfully, the Knative Service is operable at the URL specified in the command output.

Deploying your application to a local Kubernetes cluster

If you have installed a Kubernetes cluster on your development workstation and want to use your local Docker image cache instead of pushing the image to Docker Hub, make sure you set up your Kubernetes cluster to consume images from the local Docker cache.

To deploy your Appsody project locally, run:

appsody deploy

This command completes the following actions:

  • Calls appsody build and creates a deployment Docker image and a manifest file named app-deploy.yaml, as described in the previous section.
  • If you specified the --knative flag, or if Knative is the only deployment option for your stack, the command tags the image with the special prefix dev.local, making it accessible to your Kubernetes cluster (assuming you followed these directions)
  • The deployment manifest, app-deploy.yaml, is used to issue a kubectl apply -f command against the target Kubernetes cluster so that the application can be deployed by the Appsody Operator.

Deploying your application through Docker Hub

If your cluster is configured to pull images from Docker Hub, use the following command to deploy your application:

appsody deploy -t <mynamespace/myrepository[:tag]> --push --namespace mynamespace [--knative]

The command completes the following actions:

  • Calls appsody build and creates a deployment image, as described in the previous section.
  • The -t mynamespace/myrepository[:tag] flag tags the image.
  • The --push flag tells the Appsody CLI to push the image to Docker Hub.
  • Creates a deployment manifest file named app-deploy.yaml in the project directory, if one doesn’t exist already. If a deployment manifest file exists, this command updates the following entries within it: application image, labels, and annotations. In addition, the createKnativeService entry is set to true if you specified the --knative flag.
  • The Yaml file is used to issue a kubectl apply -f command against the target Kubernetes cluster. The Yaml file is set to use the Appsody operator.
  • The --namespace mynamespace option provisions the deployment under the specified Kubernetes namespace within your cluster.

If you don't specify --push, the image is available only on your local Docker registry and the target Kubernetes cluster must be configured to have access to your local Docker registry.

Deploying your application to a custom registry

If your cluster is configured to pull images from a custom registry, use the following command to deploy your application:

appsody deploy -t <mynamespace/myrepository[:tag]> --push-url <registry-url:PORT>

If you are specifying different push and pull registries, for example, you might want to push to an external registry and pull from an internal registry, use the following command:

appsody deploy -t <mynamespace/myrepository[:tag]> --push-url <external-registry-url:PORT> --pull-url <internal-registry-url:PORT>

Note: The pull registry url gets injected into the deployment manifest for Kubernetes to pull the correct image.

Deploying multiple projects

If you are running multiple Appsody projects on your workstation, you can use appsody deploy and appsody operator commands to get them deployed to a Kubernetes cluster. However, make sure that you run these commands one at a time, because those commands create temporary files that might lead to conflicts if created concurrently.

Ensuring the latest application code changes get deployed

Some users have noticed that their code changes do not seem to be published to the target Kubernetes cluster after an initial deployment of the Appsody project through appsody deploy. The sequence of actions that leads to this behavior is as follows:

  1. You create an initial version of your app, and then use appsody deploy to publish it to your test Kubernetes cluster.
  2. You test your app, and make code changes. The code changes appear as you re-test your app using appsody run.
  3. You decide to re-publish your app to your target cluster, and run appsody deploy again.
  4. The command succeeds, yet nothing seems to change on the Kubernetes cluster: you still observe the older version of your app.

This behavior can be explained by the fact that - if you simply issue appsody deploy without explicitly tagging the image - you end up with a deployment manifest (the app-deploy.yaml file) that is identical to the one that was used to deploy the application the first time. Therefore, Kubernetes will detect no differences in the deployment yaml, and will do nothing to update your app.

To ensure that the latest version of your app is pushed to the cluster, use the -t flag to add a unique tag every time you redeploy your app. Kubernetes then detects a change in the deployment manifest, and pushes your app to the cluster again. For example: appsody deploy -t dev.local/my-image:0.x, where x is a number that you increment every time you redeploy.

Deploying your app through a Tekton pipeline

This deployment option is under development

Most likely, the deployment of apps created with the Appsody CLI is going to occur through the invocation of a CI/CD build pipeline.

As a developer, you develop your app using the Appsody CLI, and when you are ready to deploy, you push your code to a repo or create a pull request on GitHub.

This example shows you how to use Tekton pipelines to deploy your app to a Kubernetes cluster. More details on running the Tekton pipeline example for Appsody can be found in the repo readme file. The example uses a customized Buildah image with the Appsody CLI installed. For more information on using Appsody with Buildah, see the FAQ.