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 easily.

You can operate entirely without openapi definitions if you are operating on a CustomResource, but if you require the full definitions of native objects, it is easier to compile with the openapi feature to get accurate struct representations via k8s-openapi.

Installation

To use the openapi generated types:

[dependencies]
kube = { version = "0.21.2", features = ["openapi"] }
k8s-openapi = { version = "0.6.0", default-features = false, features = ["v1_15"] }

otherwise:

[dependencies]
kube = "0.21.2"

The latter is fine in a CRD-only use case.

Usage

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

API Docs

See version-rs for a super light (~100 lines), actix*, prometheus, deployment api setup.

See controller-rs for a full actix* example, with circleci, and kube yaml.

NB: actix examples have not been updated to the async version of this library yet.

Api

It's currently recommended to compile with the "openapi" feature if you want an easy experience with accurate native object representations:

let pods = Api::v1Pod(client).within("default");

let p = pods.get("blog").await?;
println!("Got blog pod with containers: {:?}", p.spec.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 pod_openapi or crd_openapi examples for more uses.

Informer

The main abstraction from kube::api is Informer<K>. This is a struct with the internal behaviour for watching kube resources, but maintains only a queue of WatchEvent elements along with the last seen resourceVersion.

You tell it what type KubeObject implementing object you want to use. You can use Object<P, U> to get an automatic implementation by using Object<PodSpec, PodStatus>.`

The spec and status structs can be as complete or incomplete as you like. For instance, using the complete structs from k8s-openapi:

type Pod = Object<PodSpec, PodStatus>;
let api = Api::v1Pod(client);
let inf = Informer::new(api.clone()).init().await?;

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

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

while let Some(event) = pods.next().await { // await next event
    handle_event(&api, event?).await?; // pass the WatchEvent to a handler
}

How you handle them is up to you, you could build your own state, you can call a kube client, or you can simply print events. Here's a sketch of how such a handler would look:

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

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

Reflector

The other big abstractions exposed from kube::api is Reflector<K>. This is a cache of a resource that's meant to "reflect the resource state in etcd".

It handles the api mechanics for watching kube resources, tracking resourceVersions, and using watch events; it builds and maintains an internal map.

To use it, you just feed in T as a Spec struct and U as a Status struct, which can be as complete or incomplete as you like. Here, using the complete structs via k8s-openapi's PodSpec:

let api = Api::v1Pod(client).within(&namespace);
let rf = Reflector::new(api).timeout(10).init().await?;

then you should poll() the reflector, and state() to get the current cached state:

rf.poll().await?; // watches + updates state

// Clone state and do something with it
rf.state().await.into_iter().for_each(|(name, p)| {
    println!("Found pod {} ({}) with {:?}",
        name,
        p.status.unwrap().phase.unwrap(),
        p.spec.containers.into_iter().map(|c| c.name).collect::<Vec<_>>(),
    );
});

Note that poll holds the future for 300s by default, but you can (and should) get .state() from another async context (see reflector examples for how to spawn an async task to do this).

If you need the details of just a single object, you can use the more efficient, Reflector::get and Reflector::get_within.

Examples

Examples that show a little common flows. These all have logging of this library set up to trace:

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

or for the reflectors:

cargo run --example pod_reflector --features=openapi
cargo run --example node_reflector --features=openapi
cargo run --example deployment_reflector --features=openapi
cargo run --example secret_reflector --features=openapi
cargo run --example configmap_reflector --features=openapi

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

kubectl apply -f examples/foo.yaml
cargo run --example crd_reflector --no-default-features

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 --no-default-features
cargo run --example crd_openapi --features=openapi
cargo run --example pod_openapi --features=openapi

Timing

All watch calls have timeouts set to 10 seconds as a default (and kube always waits that long regardless of activity). If you like to hammer the API less, you can either call .poll() less often and the events will collect on the kube side (if you don't wait too long and get a Gone). You can configure the timeout with .timeout(n) on the Informer or Reflector.

Raw Api

You can elide the large k8s-openapi dependency if you only are working with Informers/Reflectors, or you are happy to supply partial or complete definitions of the native objects you are working with:

#[derive(Deserialize, Serialize, Clone)]
pub struct FooSpec {
    name: String,
    info: String,
}
let foos = RawApi::customResource("foos")
    .version("v1")
    .group("clux.dev")
    .within("default");

type Foo = Object<FooSpec, Void>;
let rf : Reflector<Foo> = Reflector::raw(client, resource).init().await?;

let fdata = json!({
    "apiVersion": "clux.dev/v1",
    "kind": "Foo",
    "metadata": { "name": "baz" },
    "spec": { "name": "baz", "info": "old baz" },
});
let req = foos.create(&PostParams::default(), serde_json::to_vec(&fdata)?)?;
let o = client.request::<Foo>(req).await?;

let fbaz = client.request::<Foo>(foos.get("baz")?).await?;
assert_eq!(fbaz.spec.info, "old baz");

If you supply a partial definition of native objects then you can save on reflector memory usage.

The node_informer and crd_reflector examples uses this at the moment , (although node_informer is cheating by supplying k8s_openapi structs manually anyway). The crd_api example also shows how to do it for CRDs.

License

Apache 2.0 licensed. See LICENSE for details.