# Tendermint network powered by Kubernetes

![Tendermint plus Kubernetes](img/t_plus_k.png)

* [QuickStart (MacOS)](#quickstart-macos)
* [QuickStart (Linux)](#quickstart-linux)
* [Usage](#usage)
* [Security](#security)
* [Fault tolerance](#fault-tolerance)
* [Starting process](#starting-process)

This should primarily be used for testing purposes or for tightly-defined
chains operated by a single stakeholder (see [the security
precautions](#security)). If your desire is to launch an application with many
stakeholders, consider using our set of Ansible scripts.

## QuickStart (MacOS)

[Requirements](https://github.com/kubernetes/minikube#requirements)

```
curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/darwin/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/kubectl
curl -Lo minikube https://storage.googleapis.com/minikube/releases/v0.17.1/minikube-darwin-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
minikube start

git clone https://github.com/tendermint/tools.git && cd tools/mintnet-kubernetes/examples/basecoin && make create
```

## QuickStart (Linux)

[Requirements](https://github.com/kubernetes/minikube#requirements)

```
curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/kubectl
curl -Lo minikube https://storage.googleapis.com/minikube/releases/v0.17.1/minikube-linux-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
minikube start

git clone https://github.com/tendermint/tools.git && cd tools/mintnet-kubernetes/examples/basecoin && make create
```

### Verify everything works

**Using a shell:**

1. wait until all the pods are `Running`.

   ```
   kubectl get pods -w -o wide -L tm
   ```

2. query the Tendermint app logs from the first pod.

   ```
   kubectl logs -c tm -f tm-0
   ```

3. use [Rest API](https://tendermint.com/docs/internals/rpc) to fetch the
   status of the second pod's Tendermint app. Note we are using `kubectl exec`
   because pods are not exposed (and should not be) to the outer network.

   ```
   kubectl exec -c tm tm-0 -- curl -s http://tm-1.basecoin:46657/status | json_pp
   ```

**Using the dashboard:**

```
minikube dashboard
```

### Clean up

```
make destroy
```

## Usage

### (1/4) Setup a Kubernetes cluster

- locally using [Minikube](https://github.com/kubernetes/minikube)
- on GCE with a single click in the web UI
- on AWS using [Kubernetes Operations](https://github.com/kubernetes/kops/blob/master/docs/aws.md)
- on Linux machines (Digital Ocean) using [kubeadm](https://kubernetes.io/docs/getting-started-guides/kubeadm/)
- on AWS, Azure, GCE or bare metal using [Kargo (Ansible)](https://kubernetes.io/docs/getting-started-guides/kargo/)

Please refer to [the official
documentation](https://kubernetes.io/docs/getting-started-guides/) for overview
and comparison of different options. See our guides for [Google Cloud
Engine](docs/SETUP_K8S_ON_GCE.md) or [Digital Ocean](docs/SETUP_K8S_ON_DO.md).

**Make sure you have Kubernetes >= 1.5, because you will be using StatefulSets,
which is a beta feature in 1.5.**

### (2/4) Create a configuration file

Download a template:

```
curl -Lo app.yaml https://github.com/tendermint/tools/raw/master/mintnet-kubernetes/app.template.yaml
```

Open `app.yaml` in your favorite editor and configure your app container
(navigate to `- name: app`). Kubernetes DSL (Domain Specific Language) is very
simple, so it should be easy. You will need to set Docker image, command and/or
run arguments. Replace variables prefixed with `YOUR_APP` with corresponding
values. Set genesis time to now and preferable chain ID in ConfigMap.

Please note if you are changing `replicas` number, do not forget to update
`validators` set in ConfigMap. You will be able to scale the cluster up or down
later, but new pods (nodes) won't become validators automatically.

### (3/4) Deploy your application

```
kubectl create -f ./app.yaml
```

### (4/4) Observe your cluster

**web UI** <-> https://github.com/kubernetes/dashboard

The easiest way to access Dashboard is to use kubectl. Run the following command in your desktop environment:

```
kubectl proxy
```

kubectl will handle authentication with apiserver and make Dashboard available at [http://localhost:8001/ui](http://localhost:8001/ui)

**shell**

List all the pods:

```
kubectl get pods -o wide -L tm
```

StatefulSet details:

```
kubectl describe statefulsets tm
```

First pod details:

```
kubectl describe pod tm-0
```

Tendermint app logs from the first pod:

```
kubectl logs tm-0 -c tm -f
```

App logs from the first pod:

```
kubectl logs tm-0 -c app -f
```

Status of the second pod's Tendermint app:

```
kubectl exec -c tm tm-0 -- curl -s http://tm-1.<YOUR_APP_NAME>:46657/status | json_pp
```

## Security

Due to the nature of Kubernetes, where you typically have a single master, the
master could be a SPOF (Single Point Of Failure). Therefore, you need to make
sure only authorized people can access it. And these people themselves had
taken basic measures in order not to get hacked.

These are the best practices:

- all access to the master is over TLS
- access to the API Server is X.509 certificate or token based
- etcd is not exposed directly to the cluster
- ensure that images are free of vulnerabilities ([1](https://github.com/coreos/clair))
- ensure that only authorized images are used in your environment
- disable direct access to Kubernetes nodes (no SSH)
- define resource quota

Resources:

- https://kubernetes.io/docs/admin/accessing-the-api/
- http://blog.kubernetes.io/2016/08/security-best-practices-kubernetes-deployment.html
- https://blog.openshift.com/securing-kubernetes/

## Fault tolerance

Having a single master (API server) is a bad thing also because if something
happens to it, you risk being left without an access to the application.

To avoid that you can [run Kubernetes in multiple
zones](https://kubernetes.io/docs/admin/multiple-zones/), each zone running an
[API server](https://kubernetes.io/docs/admin/high-availability/) and load
balance requests between them. Do not forget to make sure only one instance of
scheduler and controller-manager are running at once.

Running in multiple zones is a lightweight version of a broader [Cluster
Federation feature](https://kubernetes.io/docs/admin/federation/). Federated
deployments could span across multiple regions (not zones). We haven't tried
this feature yet, so any feedback is highly appreciated! Especially, related to
additional latency and cost of exchanging data between the regions.

Resources:

- https://kubernetes.io/docs/admin/high-availability/

## Starting process

![StatefulSet](img/statefulset.png)

Init containers (`tm-gen-validator`) are run before all other containers,
creating public-private key pair for each pod. Every `tm` container then asks
other pods for their public keys, which are served with nginx (`pub-key`
container). When `tm` container have all the keys, it forms a genesis file and
starts Tendermint process.

## TODO

- [ ] run tendermint from tmuser
  ```
  securityContext:
    fsGroup: 999
  ```