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Initial release of kubehost
By William Denniss, Van Tu and Cong Liu.
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‎AUTHORS‎

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# This is the official list of the Kubehost authors for copyright purposes.
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# This file is distinct from the CONTRIBUTORS files.
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# See the latter for an explanation.
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# Names should be added to this file as:
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# Name or Organization <email address>
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# The email address is not required for organizations.
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Google LLC

‎CONTRIBUTING.md‎

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# How to Contribute
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We'd love to accept your patches and contributions to this project. There are
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just a few small guidelines you need to follow.
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## Contributor License Agreement
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Contributions to this project must be accompanied by a Contributor License
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Agreement. You (or your employer) retain the copyright to your contribution;
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this simply gives us permission to use and redistribute your contributions as
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part of the project. Head over to <https://cla.developers.google.com/> to see
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your current agreements on file or to sign a new one.
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You generally only need to submit a CLA once, so if you've already submitted one
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(even if it was for a different project), you probably don't need to do it
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again.
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## Code reviews
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All submissions, including submissions by project members, require review. We
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use GitHub pull requests for this purpose. Consult
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[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
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information on using pull requests.
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## Community Guidelines
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This project follows [Google's Open Source Community
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Guidelines](https://opensource.google.com/conduct/).

‎CONTRIBUTORS‎

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# People who have agreed to one of the CLAs and can contribute patches.
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# The AUTHORS file lists the copyright holders; this file
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# lists people. For example, Google employees are listed here
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# but not in AUTHORS, because Google holds the copyright.
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#
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# https://developers.google.com/open-source/cla/individual
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# https://developers.google.com/open-source/cla/corporate
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#
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# Names should be added to this file as:
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# Name <email address>
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William Denniss <wdenniss@google.com>
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Van Tu <vantu@google.com>
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Cong Liu <conliu@google.com>
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‎LICENSE‎

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‎README.md‎

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# kubehost
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Kubehost helps you expose services directly on nodes of your
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Google Kubernetes Engine (GKE) cluster.
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The common way to expose a service and get an external IP is
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`kubectl expose <deployment> --type=LoadBalancer"`, which will expose
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your deployment on a production-grade Google Cloud Load Balancer.
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Sometimes you just want to expose a service on your VM directly, like
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during development where uptime and reliability are not as important.
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That's where Kubehost comes in.
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Kubehost uses existing features of GKE to expose your service directly
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onto one of the VMs in your cluster, by creating a Pod that runs on
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the VM's network and forwards traffic to your in-cluster (ClusterIP)
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service, and creating firewall rules to permit external traffic.
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While you could do this manually, Kubehost takes the toil out of
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managing this configuration by automating the necessary actions.
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<br>
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> ### :warning: For development use only
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> kubehost is NOT designed for production use! Nodes in GKE
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> are designed to be redundant, meaning they can fail.
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> When the node on which your service is exposed via kubehost fails or
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> is upgraded, your service will experience several minutes of downtime.
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> By comparison, if you use a production-grade Google Cloud Load
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> Balancer (and you have enough replicas of your Pod spread over
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> multiple nodes with properly implemented health and readiness checks)
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> then a node can fail with only minimal impact to the availability of
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> your service. At any time you can upgrade to a Google Cloud Load
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> Balancer with the `kubehost upgrade` command.
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## Installation
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`kubehost` is a bash script. To install, clone this repository and add
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it to your `$PATH`, or copy `kubehost` to your `/usr/local/bin/`.
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You may need to set the executable permission, i.e. `chmod +x kubehost`.
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## Configuration
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Before using `kubehost`, you need to ensure both `gcloud` and `kubectl`
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are configured with your desired project & cluster.
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1. run `gcloud init` to select your account, project and region
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containing the GKE cluster.
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2. run
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(get-credentials)[https://cloud.google.com/sdk/gcloud/reference/container/clusters/get-credentials]
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to configure `kubectl`.
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## Exposing a Deployment with kubehost
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1. Create your deployment like normal.
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2. Create a ClusterIP service for your deployment (this is the default
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service type, so no need to specify any type), **on your desired
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external port**.
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3. Run `kubehost bind ${SERVICE}`, where `${SERVICE}` is the name of
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the Kubernetes service you created at step 2.
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What this does is create some "glue" in the form of a hostPort
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deployment so that your service is bound to port you specified in the
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service on your node's external IP (read "under the hood" for a longer
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technical description). It also opens the necessary GCP firewall rules.
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To undo, `kubehost unbind ${SERVICE}`
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Complete example:
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```bash
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kubectl run hello --image gcr.io/google-samples/hello-app:1.0 --port 8080
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kubectl expose deployment hello --port 80 --target-port 8080 --name hello-service
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kubehost bind hello-service
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```
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Cleanup:
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```bash
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kubehost unbind hello-service
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kubectl delete deployment hello
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kubectl delete service hello-service
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```
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## Switching between hostPort and a Load Balancer
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### Upgrading to a Load Balancer from hostPort
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Is your app ready for prime time? Remove the hostPort Pod "glue", and
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convert your Service into one backed by a
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[Google Cloud Load Balancer](https://cloud.google.com/load-balancing/)
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with one simple command:
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```bash
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kubehost upgrade ${SERVICE}
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```
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Where `${SERVICE}` is the name of your Cluster IP service.
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### Downgrading a Load Balancer to hostPort
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Did you already expose your service with a Load Balancer and found it's
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more than you needed? Convert it to an internal ClusterIP service,
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and expose it on a host in one command with:
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```bash
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kubehost downgrade ${SERVICE}
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```
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Where `${SERVICE}` is the name of your Kubernetes service of type
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LoadBalancer.
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## Limitations
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* Kubehost currently works with services that have a single port. If you
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need to expose two ports, create two ClusterIP services.
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* Kubehost is not designed for production usage, see the note above.
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* Kubehost doesn't give you a static IP. The IP address of node may
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change which will affect your service. You can create a static IP
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and use the [kubeIP](https://github.com/doitintl/kubeIP) operator to
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keep it assigned through node maintenance events.
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## Under the Hood
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What Kubehost is doing when you call `bind` is creating
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a Kubernetes Deployment with a single replica of a Pod that uses
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hostPort to bind onto the host's network interface. The container in
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this Pod forwards traffic to your ClusterIP service.
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While you could instead change your deployment to use hostPort directly
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we think this approach is superior, as:
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1. It's closer to the production Kubernetes experience where deployments
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have a matching service to receive traffic.
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2. It's easier to switch between this and a production setup by
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changing the Service type to LoadBalancer, and removing the hostPort
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deployment (and vice-versa) – no need to modify your application
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deployment.
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3. Your deployment's replica count isn't limited by available ports.

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