Don't restart pods on some config changes

api/v1alpha1/conditions.go

@@ -37,6 +37,8 @@ const (
 	// ConditionTypeConfigurationInSync indicates that cluster configuration is in desired state.
 	ConditionTypeConfigurationInSync    ConditionType   = "ConfigurationInSync"
 	ConditionReasonConfigurationChanged ConditionReason = "ConfigurationChanged"
+	ConditionReasonConfigReloadFailed   ConditionReason = "ConfigReloadFailed"
+	ConditionReasonConfigReloadPending  ConditionReason = "ConfigReloadPending"
 
 	// ConditionTypeVersionInSync indicates that all replicas report the same version as the image.
 	ConditionTypeVersionInSync        ConditionType   = "VersionInSync"

internal/controller/clickhouse/commands.go

@@ -87,23 +87,50 @@ func (cmd *commander) Close() {
 	cmd.conns = map[v1.ClickHouseReplicaID]clickhouse.Conn{}
 }
 
-func (cmd *commander) Version(ctx context.Context, id v1.ClickHouseReplicaID) (string, error) {
+type replicaProbe struct {
+	Version              string
+	ReloadConfigRevision string
+}
+
+// Probe reads the replica server version and the latest applied reload-safe config revision.
+func (cmd *commander) Probe(ctx context.Context, id v1.ClickHouseReplicaID) (replicaProbe, error) {
 	conn, err := cmd.getConn(id)
 	if err != nil {
-		return "", fmt.Errorf("failed to get connection for replica %s: %w", id, err)
+		return replicaProbe{}, fmt.Errorf("failed to get connection for replica %s: %w", id, err)
 	}
 
-	var version string
-	if err := conn.QueryRow(ctx, "SELECT version()").Scan(&version); err != nil {
-		return "", fmt.Errorf("query version on replica %s: %w", id, err)
+	var probe replicaProbe
+
+	row := conn.QueryRow(ctx,
+		"SELECT version(),"+
+			" ifNull((SELECT collection[?] FROM system.named_collections WHERE name = ?), '')"+
+			" SETTINGS format_display_secrets_in_show_and_select=1",
+		OperatorConfigRevisionField, OperatorNamedCollectionName,
+	)
+	if err := row.Scan(&probe.Version, &probe.ReloadConfigRevision); err != nil {
+		return replicaProbe{}, fmt.Errorf("probe replica %s: %w", id, err)
 	}
 
-	version, err = controllerutil.ParseVersion(version)
+	probe.Version, err = controllerutil.ParseVersion(probe.Version)
 	if err != nil {
-		return "", fmt.Errorf("parse version from replica %s response: %w", id, err)
+		return replicaProbe{}, fmt.Errorf("parse version from replica %s response: %w", id, err)
 	}
 
-	return version, nil
+	return probe, nil
+}
+
+// ReloadConfig queries the replica to reload its configuration.
+func (cmd *commander) ReloadConfig(ctx context.Context, id v1.ClickHouseReplicaID) error {
+	conn, err := cmd.getConn(id)
+	if err != nil {
+		return fmt.Errorf("failed to get connection for replica %s: %w", id, err)
+	}
+
+	if err := conn.Exec(ctx, "SYSTEM RELOAD CONFIG"); err != nil {
+		return fmt.Errorf("reload config on replica %s: %w", id, err)
+	}
+
+	return nil
 }
 
 func (cmd *commander) SyncDatabases(ctx context.Context, log controllerutil.Logger, replicas []v1.ClickHouseReplicaID) bool {

internal/controller/clickhouse/commands_test.go

@@ -35,6 +35,7 @@ const (
 	testUsername                   = "operator"
 	keeperImage                    = "clickhouse/clickhouse-keeper:26.2"
 	clickhouseImage                = "clickhouse/clickhouse-server:26.2"
+	testConfigRevision             = "test-revision-v1"
 )
 
 func generateKeeperConfig() *strings.Reader {
@@ -70,8 +71,11 @@ remote_servers:
   default:
     shard:
       replica: [%s]
+named_collections:
+  __operator:
+    config_revision: %s
 display_secrets_in_show_and_select: true
-`, replica, keeperHostname, keeper.PortNative, strings.Join(replicas, ",")))
+`, replica, keeperHostname, keeper.PortNative, strings.Join(replicas, ","), testConfigRevision))
 }
 
 func generateUsersConfig() *strings.Reader {
@@ -218,12 +222,13 @@ var _ = Describe("commander", Ordered, Label("integration"), func() {
 		})
 	})
 
-	It("should get every node version", func(ctx context.Context) {
+	It("should probe version and config revision in a single query", func(ctx context.Context) {
 		for id := range cmd.cluster.ReplicaIDs() {
 			Eventually(func(g Gomega) {
-				v, err := cmd.Version(ctx, id)
+				probe, err := cmd.Probe(ctx, id)
 				g.Expect(err).NotTo(HaveOccurred())
-				g.Expect(v).To(MatchRegexp(`^\d+\.\d+\.\d+\.\d+$`))
+				g.Expect(probe.Version).To(MatchRegexp(`^\d+\.\d+\.\d+\.\d+$`))
+				g.Expect(probe.ReloadConfigRevision).To(Equal(testConfigRevision))
 			}, "1m", "100ms").Should(Succeed())
 		}
 	})