Switch to kubernetes cluster dns for incluster url everywhere (#876)

* Switch to kubernetes dns for incluster url everywhere

This is the recommended, and only documented method on https://kubernetes.io/docs/tasks/run-application/access-api-from-pod/
The legacy method has issues with ipv6 and it's time to retire it.

We trialled the new method for 6months via #587 without any reports.

Closes #874

Signed-off-by: clux <sszynrae@gmail.com>

* remove code for legacy methods, was never actually made public

Signed-off-by: clux <sszynrae@gmail.com>

* simplify kube_dns fn with less unwraps

Signed-off-by: clux <sszynrae@gmail.com>

kube-client/src/config/incluster_config.rs

@@ -1,12 +1,5 @@
-use std::env;
-
 use thiserror::Error;
 
-// Old method to connect to kubernetes
-const SERVICE_HOSTENV: &str = "KUBERNETES_SERVICE_HOST";
-const SERVICE_PORTENV: &str = "KUBERNETES_SERVICE_PORT";
-// New method to connect to kubernetes
-const SERVICE_DNS: &str = "kubernetes.default.svc";
 // Mounted credential files
 const SERVICE_TOKENFILE: &str = "/var/run/secrets/kubernetes.io/serviceaccount/token";
 const SERVICE_CERTFILE: &str = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt";
@@ -15,14 +8,6 @@ const SERVICE_DEFAULT_NS: &str = "/var/run/secrets/kubernetes.io/serviceaccount/
 /// Errors from loading in-cluster config
 #[derive(Error, Debug)]
 pub enum Error {
-    /// Required envionment variables were not set
-    #[error(
-        "missing environment variables {} and/or {}",
-        SERVICE_HOSTENV,
-        SERVICE_PORTENV
-    )]
-    MissingEnvironmentVariables,
-
     /// Failed to read the default namespace for the service account
     #[error("failed to read the default namespace: {0}")]
     ReadDefaultNamespace(#[source] std::io::Error),
@@ -40,40 +25,8 @@ pub enum Error {
     ParseCertificates(#[source] pem::PemError),
 }
 
-/// Returns Kubernetes address from specified environment variables.
-pub fn kube_server() -> Result<http::Uri, Error> {
-    kube_host_port()
-        .ok_or(Error::MissingEnvironmentVariables)?
-        .parse::<http::Uri>()
-        .map_err(Error::ParseClusterUrl)
-}
-
 pub fn kube_dns() -> http::Uri {
-    http::Uri::builder()
-        .scheme("https")
-        .authority(SERVICE_DNS)
-        .path_and_query("/")
-        .build()
-        .unwrap()
-}
-
-fn kube_host_port() -> Option<String> {
-    let host = kube_host()?;
-    let port = kube_port()?;
-    if host.contains(":") {
-        // IPv6 cluster
-        Some(format!("https://[{}]:{}", host, port))
-    } else {
-        Some(format!("https://{}:{}", host, port))
-    }
-}
-
-fn kube_host() -> Option<String> {
-    env::var(SERVICE_HOSTENV).ok()
-}
-
-fn kube_port() -> Option<String> {
-    env::var(SERVICE_PORTENV).ok()
+    http::Uri::from_static("https://kubernetes.default.svc/")
 }
 
 pub fn token_file() -> String {
@@ -90,39 +43,3 @@ pub fn load_cert() -> Result<Vec<Vec<u8>>, Error> {
 pub fn load_default_ns() -> Result<String, Error> {
     std::fs::read_to_string(&SERVICE_DEFAULT_NS).map_err(Error::ReadDefaultNamespace)
 }
-
-#[test]
-fn test_kube_host() {
-    let expected = "fake.io";
-    env::set_var(SERVICE_HOSTENV, expected);
-    assert_eq!(kube_host().unwrap(), expected);
-    kube_dns(); // verify kube_dns always unwraps
-}
-
-#[test]
-fn test_kube_port() {
-    let expected = "8080";
-    env::set_var(SERVICE_PORTENV, expected);
-    assert_eq!(kube_port().unwrap(), expected);
-}
-
-#[test]
-fn test_kube_server() {
-    let host = "fake.io";
-    let port = "8080";
-    env::set_var(SERVICE_HOSTENV, host);
-    env::set_var(SERVICE_PORTENV, port);
-    assert_eq!(kube_server().unwrap(), "https://fake.io:8080");
-}
-
-#[test]
-fn test_kube_server_ipv6() {
-    let host = "2001:0db8:85a3:0000:0000:8a2e:0370:7334";
-    let port = "8080";
-    env::set_var(SERVICE_HOSTENV, host);
-    env::set_var(SERVICE_PORTENV, port);
-    assert_eq!(
-        kube_server().unwrap(),
-        "https://[2001:0db8:85a3:0000:0000:8a2e:0370:7334]:8080"
-    );
-}

kube-client/src/config/mod.rs

@@ -192,14 +192,7 @@ impl Config {
     /// and relies on you having the service account's token mounted,
     /// as well as having given the service account rbac access to do what you need.
     pub fn from_cluster_env() -> Result<Self, InClusterError> {
-        let cluster_url = if cfg!(feature = "rustls-tls") {
-            // try rolling out new method for rustls which does not support ip based urls anyway
-            // see https://github.com/kube-rs/kube-rs/issues/587
-            incluster_config::kube_dns()
-        } else {
-            incluster_config::kube_server()?
-        };
-
+        let cluster_url = incluster_config::kube_dns();
         let default_namespace = incluster_config::load_default_ns()?;
         let root_cert = incluster_config::load_cert()?;