Avoid KeyError with warnings on old unsupported Slurm version

CHANGELOG.md

@@ -31,6 +31,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Changed
 - frontend: Add intermediate cluster list width to 80% on large screens, before
   going down to 60% on even larger screens.
+- agent: Check Slurm version returned from `slurmrestd` against hard-coded
+  minimal version and log error if not greater or equal.
 - pkgs: Add requirement on RFL.core and RFL.authentication >= 1.0.3.
 - docs: Update configuration reference documentation.
 
@@ -44,6 +46,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
     interpreted by frontend and emit clear error message in logs (#321).
   - Detect responses from slurmrestd not formatted in JSON, translated into JSON
     error for frontend and emit clear error message in logs (#333).
+  - Detect absence of _warnings_ key in `slurmrestd` responses and emit warning
+    log instead of crashing (#316).
 - genjwt: fix portability to Python < 3.8 in debug message.
 - ldap-check: fix usage of `user_name_attribute` configuration parameter (#340).
 - frontend:

slurmweb/views/agent.py

@@ -15,6 +15,9 @@
 from ..errors import SlurmwebCacheError, SlurmwebRestdError
 from . import SlurmrestdUnixAdapter
 
+# Tuple used for comparaison with Slurm version retrieved from slurmrestd and
+# check for minimal supported version.
+MINIMAL_SLURM_VERSION = (23, 2, 0)
 
 logger = logging.getLogger(__name__)
 
@@ -92,7 +95,13 @@ def slurmrest(query, key, handle_errors=True):
                 error["description"],
                 error["source"],
             )
-    if len(result["warnings"]):
+    if "warnings" not in result:
+        logger.error(
+            "Unable to extract warnings from slurmrestd response to %s, unsupported "
+            "Slurm version?",
+            query,
+        )
+    elif len(result["warnings"]):
         logger.warning("slurmrestd query %s warnings: %s", query, result["warnings"])
     return result[key]
 
@@ -131,7 +140,7 @@ def _cached_data(cache_key: str, expiration: int, func: Callable, *args: List[An
 def _get_version():
     return slurmrest(f"/slurm/v{current_app.settings.slurmrestd.version}/ping", "meta")[
         "Slurm"
-    ]["release"]
+    ]
 
 
 def _cached_version():
@@ -278,6 +287,22 @@ def _cached_accounts():
 def stats():
     total = 0
     running = 0
+
+    version = _cached_version()
+    logger.info("Retrieved version %s", version)
+    # Check Slurm version is supported or fail with HTTP/500
+    if (
+        not (
+            version["version"]["major"],
+            version["version"]["minor"],
+            version["version"]["micro"],
+        )
+        >= MINIMAL_SLURM_VERSION
+    ):
+        error = f"Unsupported Slurm version {version['release']}"
+        logger.error(error)
+        abort(500, error)
+
     for job in _cached_jobs():
         total += 1
         if "RUNNING" in job["job_state"]:
@@ -290,7 +315,7 @@ def stats():
         cores += node["cpus"]
     return jsonify(
         {
-            "version": _cached_version(),
+            "version": version["release"],
             "resources": {"nodes": nodes, "cores": cores},
             "jobs": {"running": running, "total": total},
         }