#kubernetes #openapi

bin+lib kopium

kubernetes openapi unmangler

24 releases (15 breaking)

0.16.5 Jan 9, 2024
0.16.2 Nov 7, 2023
0.15.0 Feb 17, 2023
0.14.0 Nov 18, 2022
0.2.1 Nov 29, 2021

#282 in Development tools

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1.5K SLoC


CI Crates.io dependency status

Kubernetes openapi unmangler.

Generates rust structs from customresourcedefinitions in your kubernetes cluster following the spec/status model, by using their embedded openapi schema.

⚠️ WARNING: not feature complete ⚠️



  • Instantly queryable: generated type uses kube-derive to provide api integration with kube
  • Rust doc comments: optionally extracted from description values in schema
  • Safe case conversion: generated types uses rust standard camel_case with occasional serde rename attributes
  • Usable locally and in CI: Can read crds by name in cluster via mycrd.group.io or from file via -f crd.yaml


Grab a prebuilt directly / via binstall, or install from crates.io:

cargo install kopium # from src
cargo binstall kopium # from release


If you have a crd installed in your cluster, pass a crd name accessible from your KUBECONFIG:

kopium prometheusrules.monitoring.coreos.com -A > prometheusrule.rs

Or pass a file/stdin via -f:

curl -sSL https://raw.githubusercontent.com/prometheus-operator/prometheus-operator/main/example/prometheus-operator-crd/monitoring.coreos.com_prometheusrules.yaml \
    | kopium -Af - > prometheusrule.rs


use kube::CustomResource;
use schemars::JsonSchema;
use serde::{Serialize, Deserialize};
use std::collections::BTreeMap;
use k8s_openapi::apimachinery::pkg::util::intstr::IntOrString;

/// Specification of desired alerting rule definitions for Prometheus.
#[derive(CustomResource, Serialize, Deserialize, Clone, Debug, JsonSchema)]
#[kube(group = "monitoring.coreos.com", version = "v1", kind = "PrometheusRule", plural = "prometheusrules")]
pub struct PrometheusRuleSpec {
    /// Content of Prometheus rule file
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub groups: Option<Vec<PrometheusRuleGroups>>,

/// RuleGroup is a list of sequentially evaluated recording and alerting rules.
#[derive(Serialize, Deserialize, Clone, Debug, JsonSchema)]
pub struct PrometheusRuleGroups {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub interval: Option<String>,
    pub name: String,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub partial_response_strategy: Option<String>,
    pub rules: Vec<PrometheusRuleGroupsRules>,

/// Rule describes an alerting or recording rule
#[derive(Serialize, Deserialize, Clone, Debug, JsonSchema)]
pub struct PrometheusRuleGroupsRules {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub alert: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<BTreeMap<String, String>>,
    pub expr: IntOrString,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub r#for: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub labels: Option<BTreeMap<String, String>>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub record: Option<String>,

Usage with kube

Simply add the generated file (e.g. output from above in prometheusrule.rs) to your library, and import (at least) the special root type:

use prometheusrule::PrometheusRule;
use kube::{Api, Client, ResourceExt};

async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::try_default().await?;
    let pr: Api<PrometheusRule> = Api::default_namespaced(client);
    for p in pr.list(&Default::default()).await? {
        println!("Found PrometheusRule {} in current namespace", p.name_any());


Autocompletion for most shells available via kopium completions:

source <(kopium completions bash)


Unit tests and running kopium from a file do not require a cluster and can be run with:

cargo test --lib
cargo run --bin kopium -- -f mycrd.yaml -A

Full integration tests use your current cluster to try to read a CRD and a gen object (instance of the CRD type) and parse it into the generated type:

cargo run --bin kopium -- -f prometheusrules.monitoring.coreos.com > tests/gen.rs
echo "pub type CR = PrometheusRule;" >> tests/gen.rs
kubectl apply -f tests/pr.yaml # needs to contain a CR with name "gen"
cargo test --test runner -- --nocapture

test shortcuts available via just in the justfile and run pre-merge.

Existing Bindings

Certain binding libraries publish the kopium output up to crates.io for easier consumption, and this can avoid having to inline generated files in your repo (provided you do not need customization / patches to the output).

The main catalogue library is metio/kube-custom-resources-rs which selects crds via features (don't use all-features).

Specific group binding libraries:

Feel free to edit this file to add more.


Apache 2.0 licensed. See LICENSE for details.


~806K SLoC