feat: always persist default tier

src/config.rs

@@ -772,18 +772,20 @@ pub struct ClusterConfig {
 
 impl ClusterConfig {
     pub fn tiers(&self) -> HashMap<String, Tier> {
-        if self.tiers.is_empty() {
-            return HashMap::from([(
-                DEFAULT_TIER.to_string(),
+        let mut tier_defs = HashMap::with_capacity(self.tiers.len());
+
+        let contains_default_tier_definition = self.tiers.get(DEFAULT_TIER).is_some();
+        if !contains_default_tier_definition {
+            tier_defs.insert(
+                DEFAULT_TIER.into(),
                 Tier {
                     name: DEFAULT_TIER.into(),
                     replication_factor: self.default_replication_factor(),
                     can_vote: true,
                 },
-            )]);
+            );
         }
 
-        let mut tier_defs = HashMap::with_capacity(self.tiers.len());
         for (name, info) in &self.tiers {
             let replication_factor = info
                 .replication_factor

test/int/test_config_file.py

@@ -401,3 +401,42 @@ def test_picodata_default_config(cluster: Cluster):
 
     i.start()
     i.wait_online()
+
+
+def test_default_tier_without_default_replication_factor(cluster: Cluster):
+    # default tier wasn't created only in case of explicit configuration file
+    cluster.set_config_file(
+        yaml="""
+cluster:
+    cluster_id: test
+    tiers:
+        not_default:
+"""
+    )
+
+    instance = cluster.add_instance()
+
+    dql = instance.sudo_sql(
+        'select "replication_factor" from "_pico_tier" where "name" = \'default\''
+    )
+    assert dql["rows"][0][0] == 1
+
+
+def test_default_tier_with_default_replication_factor(cluster: Cluster):
+    # default tier wasn't created only in case of explicit configuration file
+    cluster.set_config_file(
+        yaml="""
+cluster:
+    default_replication_factor: 3
+    cluster_id: test
+    tiers:
+        not_default:
+"""
+    )
+
+    instance = cluster.add_instance()
+
+    dql = instance.sudo_sql(
+        'select "replication_factor" from "_pico_tier" where "name" = \'default\''
+    )
+    assert dql["rows"][0][0] == 3