kube-rs

Rust client for Kubernetes in the style of a more generic client-go. It makes certain assumptions about the kubernetes api to allow writing generic abstractions, and as such contains rust reinterpretations of Reflector and Informer to allow writing kubernetes controllers/watchers/operators more easily.

NB: This library is currently undergoing a lot of changes with async/await stabilizing. Please check the CHANGELOG when upgrading.

Installation

Select a version of kube along with the generated k8s api types that corresponds to your cluster version:

[dependencies]
kube = "0.35.0"
kube-derive = "0.35.0"
k8s-openapi = { version = "0.8.0", default-features = false, features = ["v1_17"] }

Note that turning off default-features for k8s-openapi is recommended to speed up your compilation (and we provide an api anyway).

Usage

See the examples directory for how to watch over resources in a simplistic way.

API Docs

Some real world examples:

• version-rs: super lightweight reflector deployment with actix 2 and prometheus metrics

• krustlet: a complete WASM running kubelet

Api

The direct Api type takes a client, and is constructed with either the ::global or ::namespaced functions:

use k8s_openapi::api::core::v1::Pod;
let pods: Api<Pod> = Api::namespaced(client, "default");

let p = pods.get("blog").await?;
println!("Got blog pod with containers: {:?}", p.spec.unwrap().containers);

let patch = json!({"spec": {
    "activeDeadlineSeconds": 5
}});
let patched = pods.patch("blog", &pp, serde_json::to_vec(&patch)?).await?;
assert_eq!(patched.spec.active_deadline_seconds, Some(5));

pods.delete("blog", &DeleteParams::default()).await?;

See the examples ending in _api examples for more detail.

Custom Resource Definitions

Working with custom resources uses automatic code-generation via proc_macros in kube-derive.

You need to #[derive(CustomResource)] and some #[kube(attrs..)] on a spec struct:

#[derive(CustomResource, Serialize, Deserialize, Default, Clone)]
#[kube(group = "clux.dev", version = "v1", namespaced)]
pub struct FooSpec {
    name: String,
    info: String,
}

Then you can use a lot of generated code as:

println!("kind = {}", Foo::KIND); // impl k8s_openapi::Resource
let foos: Api<Foo> = Api::namespaced(client, "default");
let f = Foo::new("my-foo");
println!("foo: {:?}", f)
println!("crd: {}", serde_yaml::to_string(Foo::crd());

There are a ton of kubebuilder like instructions that you can annotate with here. See the crd_ prefixed examples for more.

Runtime

The optional kube::runtime module contains sets of higher level abstractions on top of the Api and Resource types so that you don't have to do all the watch book-keeping yourself.

Informer

A basic event watcher that presents a stream of api events on a resource with a given set of ListParams. Events are received as a raw WatchEvent type.

An Informer updates the last received resourceVersion internally on every event, before shipping the event to the app. If your controller restarts, you will receive one event for every active object at startup, before entering a normal watch.

let pods: Api<Pod> = Api::namespaced(client, "default");
let inform = Informer::new(pods);

The main feature of Informer<K> is being able to subscribe to events while having a streaming .poll() open:

let pods = inform.poll().await?.boxed(); // starts a watch and returns a stream

while let Some(event) = pods.try_next().await? { // await next event
    handle(event).await?; // pass the WatchEvent to a handler
}

How you handle them is up to you, you could build your own state, you can use the Api, or just print events. In this example you get complete Pod objects:

async fn handle(event: WatchEvent<Pod>) -> anyhow::Result<()> {
    match event {
        WatchEvent::Added(o) => {
            let containers = o.spec.unwrap().containers.into_iter().map(|c| c.name).collect::<Vec<_>>();
            println!("Added Pod: {} (containers={:?})", Meta::name(&o), containers);
        },
        WatchEvent::Modified(o) => {
            let phase = o.status.unwrap().phase.unwrap();
            println!("Modified Pod: {} (phase={})", Meta::name(&o), phase);
        },
        WatchEvent::Deleted(o) => {
            println!("Deleted Pod: {}", Meta::name(&o));
        },
        WatchEvent::Error(e) => {
            println!("Error event: {:?}", e);
        },
        _ => {},
    }
    Ok(())
}

The node_informer example has an example of using api calls from within event handlers.

Reflector

A cache for K that keeps itself up to date, and runs the polling machinery itself. It does not expose events, but you can inspect the state map at any time.

let nodes: Api<Node> = Api::namespaced(client, &namespace);
let lp = ListParams::default()
    .labels("beta.kubernetes.io/instance-type=m4.2xlarge");
let rf = Reflector::new(nodes).params(lp);

then you should await rf.run() at the end of main so that it can continuously poll. If you have more than one runtime (like say more than one reflector, or perhaps a webserver like actix-rt), then await all of them within inside a futures::select.

At any point you can use a clone of the reflector instance with Reflector::get and Reflector::get_within.

Examples

Examples that show a little common flows. These all have logging of this library set up to debug, and where possible pick up on the NAMSEPACE evar.

# watch pod events
cargo run --example pod_informer
# watch event events
cargo run --example event_informer
# watch for broken nodes
cargo run --example node_informer

or for the reflectors:

cargo run --example pod_reflector
cargo run --example node_reflector
cargo run --example deployment_reflector
cargo run --example secret_reflector
cargo run --example configmap_reflector

for one based on a CRD, you need to create the CRD first:

kubectl apply -f examples/foo.yaml
cargo run --example crd_reflector

then you can kubectl apply -f crd-baz.yaml -n default, or kubectl delete -f crd-baz.yaml -n default, or kubectl edit foos baz -n default to verify that the events are being picked up.

For straight API use examples, try:

cargo run --example crd_api
cargo run --example job_api
cargo run --example log_stream
cargo run --example pod_api
NAMESPACE=dev cargo run --example log_stream -- kafka-manager-7d4f4bd8dc-f6c44

Rustls

Kube has basic support (with caveats) for rustls as a replacement for the openssl dependency. To use this, turn off default features, and enable rustls-tls:

cargo run --example pod_informer --no-default-features --features=rustls-tls

or in Cargo.toml:

[dependencies]
kube = { version = "0.35.0", default-features = false, features = ["rustls-tls"] }
k8s-openapi = { version = "0.8.0", default-features = false, features = ["v1_17"] }

This will pull in the variant of reqwest that also uses its rustls-tls feature.

License

Apache 2.0 licensed. See LICENSE for details.