Examples of how to use kube

This directory contains a number of examples showcasing various capabilities of the kube crates.

All examples can be executed with:

cargo run --example $name

Examples in general show a common flows. These all have logging of this library set up to debug, and frequently pick up on the NAMESPACE evar.

kube focused api examples

For a basic overview of how to use the Api try:

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

kube admission controller example

Admission controllers are a bit of a special beast. They don't actually need kube_client (unless you need to verify something with the api-server) or kube_runtime (unless you also build a complementing reconciler) because, by themselves, they simply get changes sent to them over https. You will need a webserver, certificates, and either your controller deployed behind a Service, or as we do here: running locally with a private ip that your k3d cluster can reach.

export ADMISSION_PRIVATE_IP=192.168.1.163
./admission_setup.sh
cargo run --example admission_controller &
kubectl apply -f admission_ok.yaml # should succeed and add a label
kubectl apply -f admission_reject.yaml # should fail

kube-derive focused examples

How deriving CustomResource works in practice, and how it interacts with the schemars dependency.

cargo run --example crd_api
cargo run --example crd_derive
cargo run --example crd_derive_schema
cargo run --example crd_derive_no_schema --no-default-features --features=native-tls

The last one opts out from the default schema feature from kube-derive (and thus the need for you to derive/impl JsonSchema).

However: without the schema feature, it's left up to you to fill in a valid openapi v3 schema, as schemas are required for v1::CustomResourceDefinitions, and the generated crd will be rejected by the apiserver if it's missing. As the last example shows, you can do this directly without schemars.

It is also possible to run the crd_api example against the legacy v1beta1 CustomResourceDefinition endpoint. To do this you need to run the example with the deprecated feature and opt out of defaults:

cargo run --example crd_api --no-default-features --features=deprecated,native-tls,kubederive

Note that these examples also contain tests for CI, and are invoked with the same parameters, but using cargo test rather than cargo run.

kube-runtime focused examples

watchers

These example watch a single resource and does some basic filtering on the watchevent stream:

# watch all configmap events in a namespace
NAMESPACE=dev cargo run --example configmap_watcher
# watch unready pods in a namespace
NAMESPACE=dev cargo run --example pod_watcher
# watch all event events
cargo run --example event_watcher
# watch deployments, configmaps, secrets in one namespace
NAMESPACE=dev cargo run --example multi_watcher
# watch broken nodes and cross reference with events api
cargo run --example node_watcher
# watch arbitrary, untyped objects across all namespaces
cargo run --example dynamic_watcher

controllers

Requires you creating the custom resource first:

kubectl apply -f configmapgen_controller_crd.yaml
cargo run --example configmapgen_controller &
kubectl apply -f configmapgen_controller_object.yaml

reflectors

These examples watch resources as well as ive a store access point:

# Watch namespace pods and print the current pod count every event
cargo run --example pod_reflector
# Watch nodes for applied events and current active nodes
cargo run --example node_reflector
# Watch namespace deployments for applied events and current deployments
cargo run --example deployment_reflector
# Watch namespaced secrets for applied events and print secret keys in a task
cargo run --example secret_reflector
# Watch namespaced configmaps for applied events and print store info in task
cargo run --example configmap_reflector
# Watch namespaced foo crs for applied events and print store info in task
cargo run --example crd_reflector

The crd_reflector will just await changes. You can run kubectl apply -f crd-baz.yaml, 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.

rustls

Disable default features and enable rustls-tls:

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