tests: validate kvstore cleanup in topic_delete_test

Partitions have various kvstore items, stored by
the raft + storage layers.  When the topic is
deleted, they should be deleted too.

Use our offline log decoder tool to inspect
the kvstore out-of-band and validate the keys
go away when the topic is deleted.

tests/rptest/tests/topic_delete_test.py

@@ -9,9 +9,8 @@
 
 from rptest.services.cluster import cluster
 from ducktape.utils.util import wait_until
-
-import time
-import re
+from ducktape.mark import parametrize
+import json
 
 from rptest.clients.types import TopicSpec
 from rptest.tests.redpanda_test import RedpandaTest
@@ -20,6 +19,75 @@
 from rptest.services.metrics_check import MetricCheck
 
 
+def get_kvstore_topic_key_counts(redpanda):
+    """
+    Count the keys in KVStore that relate to Kafka topics: this excludes all
+    internal topic items: if no Kafka topics exist, this should be zero for
+    all nodes.
+
+    :returns: dict of Node to integer
+    """
+
+    viewer_path = "python3 /opt/scripts/offline_log_viewer/viewer.py"
+    viewer_cmd = f"{viewer_path} --type kvstore --path {redpanda.DATA_DIR}"
+
+    result = {}
+    for n in redpanda.nodes:
+        kvstore_json = n.account.ssh_output(viewer_cmd, combine_stderr=False)
+        assert len(kvstore_json) > 10
+
+        kvstore_data = json.loads(kvstore_json)
+
+        excess_keys = []
+        for shard, items in kvstore_data.items():
+            keys = [i['key'] for i in items]
+
+            for k in keys:
+                if k['keyspace'] == "cluster":
+                    # Not a per-partition key
+                    continue
+
+                if k['data'].get('group', None) in [0, 1, 2]:
+                    # One of the internal topics
+                    continue
+
+                if k['data'].get('ntp', {}).get('topic', None) == 'controller':
+                    # Controller storage item
+                    continue
+
+                excess_keys.append(k)
+
+            redpanda.logger.info(
+                f"{n.name}.{shard} Excess Keys {json.dumps(excess_keys,indent=2)}"
+            )
+
+        key_count = len(excess_keys)
+        result[n] = key_count
+
+    return result
+
+
+def topic_storage_purged(redpanda, topic_name):
+    storage = redpanda.storage()
+    logs_removed = all(
+        map(lambda n: topic_name not in n.ns["kafka"].topics, storage.nodes))
+
+    if not logs_removed:
+        return False
+
+    # Once logs are removed, also do more expensive inspection of
+    # kvstore to check that per-partition kvstore contents are
+    # gone.  The user doesn't care about this, but it is important
+    # to avoid bugs that would cause kvstore to bloat through
+    # topic creation/destruction cycles.
+
+    topic_key_counts = get_kvstore_topic_key_counts(redpanda)
+    if any([v > 0 for v in topic_key_counts.values()]):
+        return False
+
+    return True
+
+
 class TopicDeleteTest(RedpandaTest):
     """
     Verify that topic deletion cleans up storage.
@@ -37,7 +105,9 @@ def __init__(self, test_context):
         self.kafka_tools = KafkaCliTools(self.redpanda)
 
     @cluster(num_nodes=3)
-    def topic_delete_test(self):
+    @parametrize(with_restart=False)
+    @parametrize(with_restart=True)
+    def topic_delete_test(self, with_restart):
         def produce_until_partitions():
             self.kafka_tools.produce(self.topic, 1024, 1024)
             storage = self.redpanda.storage()
@@ -48,16 +118,20 @@ def produce_until_partitions():
                    backoff_sec=2,
                    err_msg="Expected partition did not materialize")
 
-        self.kafka_tools.delete_topic(self.topic)
+        if with_restart:
+            # Do a restart to encourage writes and flushes, especially to
+            # the kvstore.
+            self.redpanda.restart_nodes(self.redpanda.nodes)
 
-        def topic_storage_purged():
-            storage = self.redpanda.storage()
-            return all(
-                map(lambda n: self.topic not in n.ns["kafka"].topics,
-                    storage.nodes))
+        # Sanity check the kvstore checks: there should be at least one kvstore entry
+        # per partition while the topic exists.
+        assert sum(get_kvstore_topic_key_counts(
+            self.redpanda).values()) >= self.topics[0].partition_count
+
+        self.kafka_tools.delete_topic(self.topic)
 
         try:
-            wait_until(lambda: topic_storage_purged(),
+            wait_until(lambda: topic_storage_purged(self.redpanda, self.topic),
                        timeout_sec=30,
                        backoff_sec=2,
                        err_msg="Topic storage was not removed")
@@ -136,17 +210,12 @@ def check_compaction():
                 pass
             producer.free()
 
-            def topic_storage_purged():
-                storage = self.redpanda.storage()
-                return all(
-                    map(lambda n: topic_name not in n.ns["kafka"].topics,
-                        storage.nodes))
-
             try:
-                wait_until(lambda: topic_storage_purged(),
-                           timeout_sec=60,
-                           backoff_sec=2,
-                           err_msg="Topic storage was not removed")
+                wait_until(
+                    lambda: topic_storage_purged(self.redpanda, topic_name),
+                    timeout_sec=60,
+                    backoff_sec=2,
+                    err_msg="Topic storage was not removed")
 
             except:
                 # On errors, dump listing of the storage location