Add helper script to retrieve k8s releases

* get latest stable or pre-release
* get all tags
* get obsolete pre-releases

build-scripts/k8s_releases.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+
+from packaging.version import Version
+import json
+import requests
+import sys
+from typing import List
+
+K8S_TAGS_URL = "https://api.github.com/repos/kubernetes/kubernetes/tags"
+
+
+def _url_get(url: str) -> str:
+    r = requests.get(url)
+    r.raise_for_status()
+    return r.text
+
+
+def get_k8s_tags() -> List[str]:
+    """Retrieve semantically ordered k8s releases, newest to oldest."""
+    response = _url_get(K8S_TAGS_URL)
+    tags_json = json.loads(response)
+    if len(tags_json) == 0:
+        raise Exception("No k8s tags retrieved.")
+    tag_names = [tag['name'] for tag in tags_json]
+    # Github already sorts the tags semantically but let's not rely on that.
+    tag_names.sort(key=lambda x: Version(x), reverse=True)
+    return tag_names
+
+
+# k8s release naming:
+# * alpha:  v{major}.{minor}.{patch}r-alpha.{version}
+# * beta:   v{major}.{minor}.{patch}r-beta.{version}
+# * rc:     v{major}.{minor}.{patch}r-rc.{version}
+# * stable: v{major}.{minor}.{patch}
+def is_stable_release(release: str):
+    return "-" not in release
+
+
+def get_latest_stable() -> str:
+    k8s_tags = get_k8s_tags()
+    for tag in k8s_tags:
+        if is_stable_release(tag):
+            return tag
+    raise Exception(
+        "Couldn't find stable release, received tags: %s" % k8s_tags)
+
+
+def get_latest_release() -> str:
+    k8s_tags = get_k8s_tags()
+    return k8s_tags[0]
+
+
+def get_obsolete_prereleases() -> List[str]:
+    """Return obsolete K8s pre-releases.
+
+    We only keep the latest pre-release if there is no corresponding stable
+    release. All previous pre-releases are discarded.
+    """
+    k8s_tags = get_k8s_tags()
+    if not is_stable_release(k8s_tags[0]):
+        # Valid pre-release
+        k8s_tags = k8s_tags[1:]
+    # Discard all other pre-releases.
+    return [tag for tag in k8s_tags if not is_stable_release(tag)]
+
+
+# Rudimentary CLI that exposes these functions to shell scripts or GH actions.
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        sys.stderr.write(f"Usage: {sys.argv[0]} <function>\n")
+        sys.exit(1)
+    f = locals()[sys.argv[1]]
+    out = f()
+    if isinstance(out, (list, tuple)):
+        for item in out:
+            print(item)
+    else:
+        print(out)