Fix configuration compatibility issues

Summary:

Making sure a single node server v1.2 can still work
with a v1.1.6 config

crates/local-cluster-runner/Cargo.toml

@@ -16,7 +16,7 @@ workspace-hack = { version = "0.1", path = "../../workspace-hack" }
 restate-core = { workspace = true }
 restate-metadata-server = { workspace = true }
 # nb features here will also affect the compiled restate-server binary in integration tests
-restate-types = { workspace = true, features = ["unsafe-mutable-config"] }
+restate-types = { workspace = true, features = ["unsafe-mutable-config", "test-util"] }
 
 anyhow = { workspace = true }
 arc-swap = { workspace = true }

crates/local-cluster-runner/src/node/mod.rs

@@ -180,11 +180,13 @@ impl Node {
         base_config.common.auto_provision = false;
         base_config.common.log_disable_ansi_codes = true;
         if !matches!(
-            base_config.metadata_server.kind,
+            base_config.metadata_server.kind(),
             MetadataServerKind::Raft(_)
         ) {
             info!("Setting the metadata server to embedded");
-            base_config.metadata_server.kind = MetadataServerKind::Raft(RaftOptions::default());
+            base_config
+                .metadata_server
+                .set_kind(MetadataServerKind::Raft(RaftOptions::default()));
         }
 
         for node_id in 1..=size {

crates/metadata-server/src/lib.rs

@@ -188,7 +188,7 @@ pub async fn create_metadata_server(
     server_builder: &mut NetworkServerBuilder,
 ) -> anyhow::Result<BoxedMetadataServer> {
     metric_definitions::describe_metrics();
-    match metadata_server_options.kind {
+    match metadata_server_options.kind() {
         MetadataServerKind::Local => LocalMetadataServer::create(
             metadata_server_options,
             rocksdb_options,

crates/metadata-server/src/raft/server.rs

@@ -540,7 +540,8 @@ impl Member {
         connection_manager.store(Some(Arc::new(new_connection_manager)));
 
         let_assert!(
-            MetadataServerKind::Raft(raft_options) = &Configuration::pinned().metadata_server.kind,
+            MetadataServerKind::Raft(raft_options) =
+                &Configuration::pinned().metadata_server.kind(),
             "Expecting that the replicated/raft metadata server has been configured"
         );
 

crates/types/src/config/common.rs

@@ -628,6 +628,7 @@ enum MetadataClientKindShadow {
     #[serde(alias = "embedded")]
     Native {
         address: Option<AdvertisedAddress>,
+        #[serde(default)]
         addresses: Vec<AdvertisedAddress>,
     },
     Etcd {
@@ -657,8 +658,14 @@ impl TryFrom<MetadataClientKindShadow> for MetadataClientKind {
 
                 Self::Native {
                     addresses: match address {
-                        Some(address) if addresses == vec![default_address] => vec![address],
-                        Some(_) => return Err("Conflicting configuration, embedded metadata-store-client cannot have both `address` and `addresses`"),
+                        Some(address)
+                            if addresses.is_empty() || addresses == vec![default_address] =>
+                        {
+                            vec![address]
+                        }
+                        Some(_) => {
+                            return Err("Conflicting configuration, embedded metadata-store-client cannot have both `address` and `addresses`");
+                        }
                         None => addresses,
                     },
                 }

crates/types/src/config/metadata_server.rs

@@ -58,8 +58,9 @@ pub struct MetadataServerOptions {
     /// Type of metadata server to start
     ///
     /// The type of metadata server to start when running the metadata store role.
+    // defined as Option<_> for backward compatibility with version < v1.2
     #[serde(flatten)]
-    pub kind: MetadataServerKind,
+    kind: Option<MetadataServerKind>,
 }
 
 #[derive(Debug, Default, Clone, Serialize, Deserialize, PartialEq)]
@@ -78,6 +79,15 @@ pub enum MetadataServerKind {
 }
 
 impl MetadataServerOptions {
+    pub fn kind(&self) -> MetadataServerKind {
+        self.kind.clone().unwrap_or_default()
+    }
+
+    #[cfg(any(test, feature = "test-util"))]
+    pub fn set_kind(&mut self, kind: MetadataServerKind) {
+        self.kind = Some(kind);
+    }
+
     pub fn apply_common(&mut self, common: &CommonOptions) {
         self.rocksdb.apply_common(&common.rocksdb);
 
@@ -126,7 +136,7 @@ impl Default for MetadataServerOptions {
             rocksdb_memory_budget: None,
             rocksdb_memory_ratio: 0.01,
             rocksdb,
-            kind: MetadataServerKind::default(),
+            kind: Some(MetadataServerKind::default()),
         }
     }
 }

server/tests/raft_metadata_cluster.rs

@@ -119,11 +119,13 @@ async fn raft_metadata_cluster_chaos_test() -> googletest::Result<()> {
     let num_nodes = 3;
     let chaos_duration = Duration::from_secs(20);
     let mut base_config = Configuration::default();
-    base_config.metadata_server.kind = MetadataServerKind::Raft(RaftOptions {
-        raft_election_tick: NonZeroUsize::new(5).expect("5 to be non zero"),
-        raft_heartbeat_tick: NonZeroUsize::new(2).expect("2 to be non zero"),
-        ..RaftOptions::default()
-    });
+    base_config
+        .metadata_server
+        .set_kind(MetadataServerKind::Raft(RaftOptions {
+            raft_election_tick: NonZeroUsize::new(5).expect("5 to be non zero"),
+            raft_heartbeat_tick: NonZeroUsize::new(2).expect("2 to be non zero"),
+            ..RaftOptions::default()
+        }));
 
     let nodes = Node::new_test_nodes(
         base_config,