Add K8s 1.31 to CI by pinning kops commit

Author: AndrewSirenko

hack/e2e/config.sh

@@ -35,7 +35,7 @@ OUTPOST_INSTANCE_TYPE=${OUTPOST_INSTANCE_TYPE:-${INSTANCE_TYPE}}
 # kops: must include patch version (e.g. 1.19.1)
 # eksctl: mustn't include patch version (e.g. 1.19)
 # NOTE: Keep KOPS at v1.29.x until ELB usage bug fixed
-K8S_VERSION_KOPS=${K8S_VERSION_KOPS:-1.29.6}
+K8S_VERSION_KOPS=${K8S_VERSION_KOPS:-1.31.1}
 K8S_VERSION_EKSCTL=${K8S_VERSION_EKSCTL:-1.30}
 
 EBS_INSTALL_SNAPSHOT=${EBS_INSTALL_SNAPSHOT:-"true"}

hack/e2e/kops/kops.sh

@@ -19,6 +19,8 @@
 
 set -euo pipefail
 
+export KOPS_RUN_TOO_NEW_VERSION=true
+
 function kops_create_cluster() {
   CLUSTER_NAME=${1}
   KOPS_BIN=${2}

hack/tools/install.sh

@@ -33,8 +33,8 @@ GOMPLATE_VERSION="v4.1.0"
 # https://github.com/helm/helm
 HELM_VERSION="v3.15.4"
 # https://github.com/kubernetes/kops
-# NOTE: Keep at v1.29.0 until ELB usage bug fixed
-KOPS_VERSION="v1.29.0"
+# NOTE: We pin kops to a commit instead of a release to support newer versions of k8s earlier
+KOPS_COMMIT="2f877fcf5755b8c6f6a2d937cb1f62dea3a9536a"
 # https://pkg.go.dev/sigs.k8s.io/kubetest2?tab=versions
 KUBETEST2_VERSION="v0.0.0-20240703180642-53f3d216ad9f"
 # https://github.com/golang/mock
@@ -153,9 +153,10 @@ function install_helm() {
 }
 
 function install_kops() {
+  # Build from source so we can test latest Kubernetes version earlier.
   INSTALL_PATH="${1}"
 
-  install_binary "${INSTALL_PATH}" "https://github.com/kubernetes/kops/releases/download/${KOPS_VERSION}/kops-${OS}-${ARCH}" "kops"
+  install_go "${INSTALL_PATH}" "k8s.io/kops/cmd/kops@${KOPS_COMMIT}"
 }
 
 function install_kubetest2() {