[experiments] Make monitoring_experiment never expire (#33250)

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src/core/lib/experiments/experiments.yaml

@@ -72,7 +72,7 @@
   test_tags: ["core_end2end_test", "event_engine_client_test"]
 - name: monitoring_experiment
   description: Placeholder experiment to prove/disprove our monitoring is working
-  expiry: 2023/11/01
+  expiry: never-ever
   owner: ctiller@google.com
   test_tags: []
 - name: promise_based_client_call

tools/codegen/core/gen_experiments.py

@@ -102,6 +102,11 @@ for attr in attrs:
     if 'expiry' not in attr:
         print("no expiry for experiment %s" % attr['name'])
         error = True
+    if attr['name'] == 'monitoring_experiment':
+        if attr['expiry'] != 'never-ever':
+            print("monitoring_experiment should never expire")
+            error = True
+    else:
         expiry = datetime.datetime.strptime(attr['expiry'], '%Y/%m/%d').date()
         if check_dates:
             if expiry < today: