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Jun 21, 2018
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Clarify Kubernetes Deployment Options, add Initial Istio Documentation #577

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Updated doc to clarify Kubernetes deployment options, and added Istio…
Jun 10, 2018
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Fixed a few characters
Jun 11, 2018
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Update kubernetes.md
saturnism Jun 13, 2018
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45 changes: 41 additions & 4 deletions pages/kubernetes.md
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- /kubernetes.html
sitemap:
priority: 0.7
lastmod: 2016-08-12T00:00:00-00:00
lastmod: 2018-06-10T00:00:00-00:00
---

# Deploying to Kubernetes


This sub-generator allows deployment of your JHipster application to [Kubernetes](http://kubernetes.io/).

[![]({{ site.url }}/images/logo/logo-kubernetes.png)](http://kubernetes.io/)
Expand Down Expand Up @@ -67,10 +66,13 @@ See the documentation on namespace [here](http://kubernetes.io/docs/user-guide/n

If you choose [Docker Hub](https://hub.docker.com/) as main registry, it will be your Docker Hub login.

If you choose [Google Container Registry](https://cloud.google.com/container-registry/), then it'll be `gcr.io/[PROJECT ID]`, or a regional registry, such as `eu.grc.io/[PROJECT ID]`, `us.gcr.io/[PROJECT ID]`, or `asia.gcr.io/[PROJECT ID]`. See [Pushing and Pulling Images](https://cloud.google.com/container-registry/docs/pushing-and-pulling) for more detial.

### What command should we use for push Docker image to repository?

The default command to push to Docker Hub is `docker image push`
For example, if you use the Google Cloud to host your Docker images, it will be: `gcloud docker push`

If you use Google Container Registry to host your Docker images, it will be: `gcloud docker push`

## Updating your deployed application

Expand Down Expand Up @@ -197,9 +199,44 @@ The Prometheus instance for your applications can be explored using

`kubectl get svc prometheus-appname `

## Taking Advantage of Kubernetes

Kubernetes offers a number of facilities out-of-the-box to help with Microservices deployments, such as:
* Service Registry - Kubernetes `Service` is a first-class citizen that provides service registry and lookup via DNS name.
* Load Balancing - Kubernetes Service acts as a L4 load balancer
* Health Check - Liveness probes and readiness probes help determine the health of the service.
* Configuration - Kubernetes `ConfigMap` can be used to store and apply configuration outside of the application.

There are a number of benefits of using Kubernetes facilities:
* Simplified deployment
* No need for additional Eureka/Consul deployment
* No need for Zuul to proxy/route requests
* No need for Ribbon

At the same time, there are some drawbacks:
* No Application Management through JHipster Registry - This function relies on Spring Cloud's `DiscoveryClient`. This can be updated in the future to add `spring-cloud-kubernetes`
* No local Docker Compose support - You must use `minikube` for local development, and use Ingress to route traffic
* No request-level load balancing - Kubernetes Service is a L4 load balancer that load balances per connection. Use Istio for request level load balancing (see below).

### Using Kubernetes as Service Registry

To avoid relying on Eureka or Consul, you'll need to disable service discovery altogether
* When asked `Which service discovery server do you want to use?`, simply choose `No service discovery`

A JHipster Gateway usually fronts the API calls and routing these calls using `Zuul`. Without a service registry, routing via `Zuul` won't work. You'll need to use Kubernetes `Ingress` to route the traffic to microservices.
* When asked `Choose the kubernetes service type for your edge services`, choose `Ingress`.

## Istio

You can deploy microservices into [Istio](https://istio.io)-enabled Kubernetes cluster. While Kubernetes manages microservices deployment and configuration, Istio can manage service to service communication, such as request-level load balancing, retries, circuit breakers, traffic routing/splitting, and more.

To enable Istio support:
* When asked `Do you want to configure Istio?`, choose one of the Istio options
* When asked `Do you want to generate Istio route files`, choose `Yes` to generate default configuration for circuit breaking, etc.

## Troubleshooting

> My applications don't get pulled, because of 'imagePullBackof'
> My applications don't get pulled, because of 'imagePullBackoff'

Check the registry your Kubernetes cluster is accessing. If you are using a private registry, you should add it to your namespace by `kubectl create secret docker-registry` (check the [docs](https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/) for more information).

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