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Kubernetes auto scale-up support (#29)

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This commit is contained in:
Michael Vorburger ⛑️
2022-01-07 00:41:10 +01:00
committed by GitHub
parent d7c8b4628e
commit 32fb918128
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README.md
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@@ -12,6 +12,8 @@ Routes Minecraft client connections to backend servers based upon the requested
```text
-api-binding host:port
The host:port bound for servicing API requests (env API_BINDING)
-auto-scale-up
Increase Kubernetes StatefulSet Replicas (only) from 0 to 1 on respective backend servers when accessed (env AUTO_SCALE_UP)
-connection-rate-limit int
Max number of connections to allow per second (env CONNECTION_RATE_LIMIT) (default 1)
-cpu-profile string
@@ -19,9 +21,9 @@ Routes Minecraft client connections to backend servers based upon the requested
-debug
Enable debug logs (env DEBUG)
-in-kube-cluster
Use in-cluster kubernetes config (env IN_KUBE_CLUSTER)
Use in-cluster Kubernetes config (env IN_KUBE_CLUSTER)
-kube-config string
The path to a kubernetes configuration file (env KUBE_CONFIG)
The path to a Kubernetes configuration file (env KUBE_CONFIG)
-mapping string
Comma-separated mappings of externalHostname=host:port (env MAPPING)
-metrics-backend string
@@ -61,9 +63,9 @@ Routes Minecraft client connections to backend servers based upon the requested
"backend": "HOST:PORT"
}
```
* `POST /defaultRoute` (with `Content-Type: application/json`)
Registers a default route to the given backend. JSON body is structured as:
```json
{
@@ -74,7 +76,7 @@ Routes Minecraft client connections to backend servers based upon the requested
* `DELETE /routes/{serverAddress}`
Deletes an existing route for the given `serverAddress`
# Docker Multi-Architecture Image
The [multi-architecture image published at Docker Hub](https://hub.docker.com/repository/docker/itzg/mc-router) supports amd64, arm64, and arm32v6 (i.e. RaspberryPi).
@@ -86,25 +88,25 @@ configures two Minecraft server services named `vanilla` and `forge`, which also
network aliases. _Notice those services don't need their ports exposed since the internal
networking allows for the inter-container access._
The `router` service is only one of the services that needs to exposed on the external
The `router` service is only one of the services that needs to exposed on the external
network. The `--mapping` declares how the hostname users will enter into their Minecraft client
will map to the internal services.
![](docs/compose-diagram.png)
To test out this example, I added these two entries to my "hosts" file:
```
127.0.0.1 vanilla.example.com
127.0.0.1 forge.example.com
```
# Kubernetes Usage
## Using kubernetes service auto-discovery
## Using Kubernetes Service auto-discovery
When running `mc-router` as a kubernetes pod and you pass the `--in-kube-cluster` command-line argument, then
it will automatically watch for any services annotated with
When running `mc-router` as a Kubernetes Pod and you pass the `--in-kube-cluster` command-line argument, then
it will automatically watch for any services annotated with
- `mc-router.itzg.me/externalServerName` : The value of the annotation will be registered as the external hostname Minecraft clients would used to connect to the
routed service. The service's clusterIP and target port are used as the routed backend. You can use more hostnames by splitting them with comma.
- `mc-router.itzg.me/defaultServer` : The service's clusterIP and target port are used as the default if
@@ -140,13 +142,13 @@ metadata:
"mc-router.itzg.me/externalServerName": "external.host.name,other.host.name"
```
## Example kubernetes deployment
## Example Kubernetes deployment
[This example deployment](docs/k8s-example-auto.yaml)
[This example deployment](docs/k8s-example-auto.yaml)
* Declares an `mc-router` service that exposes a node port 25565
* Declares a service account with access to watch and list services
* Declares `--in-kube-cluster` in the `mc-router` container arguments
* Two "backend" Minecraft servers are declared each with an
* Two "backend" Minecraft servers are declared each with an
`"mc-router.itzg.me/externalServerName"` annotation that declares their external server name(s)
```bash
@@ -157,8 +159,31 @@ kubectl apply -f https://raw.githubusercontent.com/itzg/mc-router/master/docs/k8
#### Notes
* This deployment assumes two persistent volume claims: `mc-stable` and `mc-snapshot`
* I extended the allowed node port range by adding `--service-node-port-range=25000-32767`
to `/etc/kubernetes/manifests/kube-apiserver.yaml`
* I extended the allowed node port range by adding `--service-node-port-range=25000-32767`
to `/etc/kubernetes/manifests/kube-apiserver.yaml`
#### Auto Scale Up
The `-auto-scale-up` flag argument makes the router "wake up" any stopped backend servers, by changing `replicas: 0` to `replicas: 1`.
This requires using `kind: StatefulSet` instead of `kind: Service` for the Minecraft backend servers.
It also requires the `ClusterRole` to permit `get` + `update` for `statefulsets` & `statefulsets/scale`,
e.g. like this (or some equivalent more fine-grained one to only watch/list services+statefulsets, and only get+update scale):
```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: services-watcher
rules:
- apiGroups: [""]
resources: ["services"]
verbs: ["watch","list"]
- apiGroups: ["apps"]
resources: ["statefulsets", "statefulsets/scale"]
verbs: ["watch","list","get","update"]
```
# Development
@@ -168,16 +193,26 @@ kubectl apply -f https://raw.githubusercontent.com/itzg/mc-router/master/docs/k8
docker build -t mc-router .
```
## Build locally without Docker
After [installing Go](https://go.dev/doc/install) and doing a `go mod download` to install all required prerequisites, just like the [Dockerfile](Dockerfile) does, you can:
```bash
make test # go test -v ./...
go build ./cmd/mc-router/
```
## Skaffold
For "in-cluster development" it's convenient to use https://skaffold.dev. Any changes to Go source code
will trigger a go build, new container image pushed to registry with a new tag, and refresh in Kubernetes
with the image tag used in the deployment transparently updated to the new tag and thus new pod created pulling new images:
with the image tag used in the deployment transparently updated to the new tag and thus new pod created pulling new images,
as configured by [skaffold.yaml](skaffold.yaml):
skaffold dev
When using Google Cloud (GCP), first create a _Docker Artifact Registry_,
then add the _Artifact Registry Reader_ Role to the _Compute Engine default service account_ of your GKE clusterService Account_ (to avoid error like "container mc-router is waiting to start: ...-docker.pkg.dev/... can't be pulled"),
then add the _Artifact Registry Reader_ Role to the _Compute Engine default service account_ of your _GKE `clusterService` Account_ (to avoid error like "container mc-router is waiting to start: ...-docker.pkg.dev/... can't be pulled"),
then use e.g. `gcloud auth configure-docker europe-docker.pkg.dev` or equivalent one time (to create a `~/.docker/config.json`),
and then use e.g. `--default-repo=europe-docker.pkg.dev/YOUR-PROJECT/YOUR-ARTIFACT-REGISTRY` option for `skaffold dev`.