Allow specifying a GKE version for running E2E tests (kubernetes#239)

scripts/README.md

@@ -101,6 +101,9 @@ project `$PROJECT_ID` and run the tests against it.
 `K8S_USER_OVERRIDE` and `DOCKER_REPO_OVERRIDE` set will immediately start the
 tests against the cluster.
 
+1. You can force running the tests against a specific GKE cluster version by using
+the `--cluster-version` flag and passing a X.Y.Z version as the flag value.
+
 ### Sample end-to-end test script
 
 This script will test that the latest Knative Serving nightly release works. It

scripts/e2e-tests.sh

@@ -84,20 +84,23 @@ function go_test_e2e() {
 
 # Download the k8s binaries required by kubetest.
 function download_k8s() {
-  local version=${SERVING_GKE_VERSION}
+  local version=${E2E_CLUSTER_VERSION}
+  # Fetch valid versions
+  local versions="$(gcloud container get-server-config \
+      --project=${GCP_PROJECT} \
+      --format='value(validMasterVersions)' \
+      --region=${E2E_CLUSTER_REGION})"
+  local gke_versions=(`echo -n ${versions//;/ /}`)
+  echo "Valid GKE versions are [${versions//;/, }]"
   if [[ "${version}" == "latest" ]]; then
-    # Fetch latest valid version
-    local versions="$(gcloud container get-server-config \
-        --project=${GCP_PROJECT} \
-        --format='value(validMasterVersions)' \
-        --region=${E2E_CLUSTER_REGION})"
-    local gke_versions=(`echo -n ${versions//;/ /}`)
     # Get first (latest) version, excluding the "-gke.#" suffix
     version="${gke_versions[0]%-*}"
-    echo "Latest GKE is ${version}, from [${versions//;/, }]"
+    echo "Using latest version, ${version}"
   elif [[ "${version}" == "default" ]]; then
     echo "ERROR: `default` GKE version is not supported yet"
     return 1
+  else
+    echo "Using command-line supplied version ${version}"
   fi
   # Download k8s to staging dir
   version=v${version}
@@ -282,6 +285,12 @@ RUN_TESTS=0
 EMIT_METRICS=0
 USING_EXISTING_CLUSTER=1
 E2E_SCRIPT=""
+E2E_CLUSTER_VERSION=""
+
+function abort() {
+  echo "error: $@"
+  exit 1
+}
 
 # Parse flags and initialize the test cluster.
 function initialize() {
@@ -291,6 +300,8 @@ function initialize() {
   E2E_SCRIPT="$(cd ${E2E_SCRIPT%/*} && echo $PWD/${E2E_SCRIPT##*/})"
   readonly E2E_SCRIPT
 
+  E2E_CLUSTER_VERSION="${SERVING_GKE_VERSION}"
+
   cd ${REPO_ROOT_DIR}
   while [[ $# -ne 0 ]]; do
     local parameter=$1
@@ -308,16 +319,22 @@ function initialize() {
     case $parameter in
       --run-tests) RUN_TESTS=1 ;;
       --emit-metrics) EMIT_METRICS=1 ;;
+      --cluster-version)
+        shift
+        [[ $# -ge 1 ]] || abort "missing version after --cluster-version"
+        [[ $1 =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]] || abort "kubernetes version must be 'X.Y.Z'"
+        E2E_CLUSTER_VERSION=$1
+        ;;
       *)
-        echo "error: unknown option ${parameter}"
-        echo "usage: $0 [--run-tests][--emit-metrics]"
-        exit 1
+        echo "usage: $0 [--run-tests][--emit-metrics][--cluster-version X.Y.Z]"
+        abort "unknown option ${parameter}"
         ;;
     esac
     shift
   done
   readonly RUN_TESTS
   readonly EMIT_METRICS
+  readonly E2E_CLUSTER_VERSION
 
   if (( ! RUN_TESTS )); then
     create_test_cluster