tests/admin_fuzzer: query all nodes about partition count

Since metadata are eventually consistent we query all nodes about
current partition count of a topic. Only if all values are the same we
allow to execute add partitions operation. This way operation result
will always be deterministic.

Fixes: redpanda-data#8637

Signed-off-by: Michal Maslanka <michal@redpanda.com>

tests/rptest/services/admin_ops_fuzzer.py

@@ -217,14 +217,32 @@ def __init__(self, prefix):
         self.total = None
         self.current = None
 
+    def _current_partition_count(self, ctx):
+
+        per_node_count = set()
+        for n in ctx.redpanda.started_nodes():
+            partitions = ctx.admin().get_partitions(node=n, topic=self.topic)
+            per_node_count.add(len(partitions))
+
+        if len(per_node_count) != 1:
+            ctx.redpanda.logger.info(
+                f"inconsistent partition count for {self.topic}: {per_node_count}"
+            )
+            return None
+
+        return next(iter(per_node_count))
+
     def execute(self, ctx):
         if self.topic is None:
             self.topic = _choice_random_topic(ctx, prefix=self.prefix)
         if self.topic is None:
             return False
+
+        if self.current is None:
+            self.current = self._current_partition_count(ctx)
+        if self.current is None:
+            return False
         if self.total is None:
-            self.current = len(
-                list(ctx.rpk().describe_topic(self.topic, tolerant=True)))
             self.total = random.randint(self.current + 1, self.current + 5)
         ctx.redpanda.logger.info(
             f"Updating topic: {self.topic} partitions count. Current partition count: {self.current} new partition count: {self.total}"