From cb6004b625fb97374831ceb0e2fc489d2e47ba06 Mon Sep 17 00:00:00 2001
From: Benny Halevy <bhalevy@scylladb.com>
Date: Thu, 26 Mar 2026 17:04:48 +0200
Subject: [PATCH] db: call initialize_virtual_tables from shard 0 only

Move the smp::invoke_on_all dispatch from the callers into
initialize_virtual_tables() itself, so the function is called
once from shard 0 and internally distributes the per-shard
virtual table setup to all shards.

This simplifies the callers and allows a single place to add
cross-shard coordination logic (e.g. feature-gated table
registration) in future commits.
---
 db/virtual_tables.cc     | 64 +++++++++++++++++++++-------------------
 main.cc                  |  4 +--
 test/lib/cql_test_env.cc |  4 +--
 3 files changed, 35 insertions(+), 37 deletions(-)

diff --git a/db/virtual_tables.cc b/db/virtual_tables.cc
index 668c4ff4fa..0b9909562f 100644
--- a/db/virtual_tables.cc
+++ b/db/virtual_tables.cc
@@ -1470,40 +1470,42 @@ future<> initialize_virtual_tables(
         sharded<service::tablet_allocator>& tablet_allocator,
         sharded<netw::messaging_service>& ms,
         db::config& cfg) {
-    auto& virtual_tables_registry = sys_ks.local().get_virtual_tables_registry();
-    auto& virtual_tables = *virtual_tables_registry;
-    auto& db = dist_db.local();
-    auto& ss = dist_ss.local();
+    co_await smp::invoke_on_all([&] () -> future<> {
+        auto& virtual_tables_registry = sys_ks.local().get_virtual_tables_registry();
+        auto& virtual_tables = *virtual_tables_registry;
+        auto& db = dist_db.local();
+        auto& ss = dist_ss.local();
 
-    auto add_table = [&] (std::unique_ptr<virtual_table>&& tbl) -> future<> {
-        auto schema = tbl->schema();
-        virtual_tables[schema->id()] = std::move(tbl);
-        co_await db.create_local_system_table(schema, false, ss.get_erm_factory());
-        auto& cf = db.find_column_family(schema);
-        cf.mark_ready_for_writes(nullptr);
-        auto& vt = virtual_tables[schema->id()];
-        cf.set_virtual_reader(vt->as_mutation_source());
-        cf.set_virtual_writer([&vt = *vt] (const frozen_mutation& m) { return vt.apply(m); });
-    };
+        auto add_table = [&] (std::unique_ptr<virtual_table>&& tbl) -> future<> {
+            auto schema = tbl->schema();
+            virtual_tables[schema->id()] = std::move(tbl);
+            co_await db.create_local_system_table(schema, false, ss.get_erm_factory());
+            auto& cf = db.find_column_family(schema);
+            cf.mark_ready_for_writes(nullptr);
+            auto& vt = virtual_tables[schema->id()];
+            cf.set_virtual_reader(vt->as_mutation_source());
+            cf.set_virtual_writer([&vt = *vt] (const frozen_mutation& m) { return vt.apply(m); });
+        };
 
-    // Add built-in virtual tables here.
-    co_await add_table(std::make_unique<cluster_status_table>(dist_ss, dist_gossiper));
-    co_await add_table(std::make_unique<token_ring_table>(db, ss));
-    co_await add_table(std::make_unique<snapshots_table>(dist_db));
-    co_await add_table(std::make_unique<protocol_servers_table>(ss));
-    co_await add_table(std::make_unique<runtime_info_table>(dist_db, ss));
-    co_await add_table(std::make_unique<versions_table>());
-    co_await add_table(std::make_unique<db_config_table>(cfg));
-    co_await add_table(std::make_unique<clients_table>(ss));
-    co_await add_table(std::make_unique<raft_state_table>(dist_raft_gr));
-    co_await add_table(std::make_unique<load_per_node>(tablet_allocator, dist_db, dist_raft_gr, ms, dist_gossiper));
-    co_await add_table(std::make_unique<tablet_sizes>(tablet_allocator, dist_db, dist_raft_gr, ms));
-    co_await add_table(std::make_unique<cdc_timestamps_table>(db, ss));
-    co_await add_table(std::make_unique<cdc_streams_table>(db, ss));
+        // Add built-in virtual tables here.
+        co_await add_table(std::make_unique<cluster_status_table>(dist_ss, dist_gossiper));
+        co_await add_table(std::make_unique<token_ring_table>(db, ss));
+        co_await add_table(std::make_unique<snapshots_table>(dist_db));
+        co_await add_table(std::make_unique<protocol_servers_table>(ss));
+        co_await add_table(std::make_unique<runtime_info_table>(dist_db, ss));
+        co_await add_table(std::make_unique<versions_table>());
+        co_await add_table(std::make_unique<db_config_table>(cfg));
+        co_await add_table(std::make_unique<clients_table>(ss));
+        co_await add_table(std::make_unique<raft_state_table>(dist_raft_gr));
+        co_await add_table(std::make_unique<load_per_node>(tablet_allocator, dist_db, dist_raft_gr, ms, dist_gossiper));
+        co_await add_table(std::make_unique<tablet_sizes>(tablet_allocator, dist_db, dist_raft_gr, ms));
+        co_await add_table(std::make_unique<cdc_timestamps_table>(db, ss));
+        co_await add_table(std::make_unique<cdc_streams_table>(db, ss));
 
-    db.find_column_family(system_keyspace::size_estimates()).set_virtual_reader(mutation_source(db::size_estimates::virtual_reader(db, sys_ks.local())));
-    db.find_column_family(system_keyspace::views_builds_in_progress()).set_virtual_reader(mutation_source(db::view::build_progress_virtual_reader(db)));
-    db.find_column_family(system_keyspace::built_indexes()).set_virtual_reader(mutation_source(db::index::built_indexes_virtual_reader(db)));
+        db.find_column_family(system_keyspace::size_estimates()).set_virtual_reader(mutation_source(db::size_estimates::virtual_reader(db, sys_ks.local())));
+        db.find_column_family(system_keyspace::views_builds_in_progress()).set_virtual_reader(mutation_source(db::view::build_progress_virtual_reader(db)));
+        db.find_column_family(system_keyspace::built_indexes()).set_virtual_reader(mutation_source(db::index::built_indexes_virtual_reader(db)));
+    });
 }
 
 virtual_tables_registry::virtual_tables_registry() : unique_ptr(std::make_unique<virtual_tables_registry_impl>()) {
diff --git a/main.cc b/main.cc
index 44678c836a..f2cad1f061 100644
--- a/main.cc
+++ b/main.cc
@@ -1963,9 +1963,7 @@ To start the scylla server proper, simply invoke as: scylla server (or just scyl
             });
 
             checkpoint(stop_signal, "initializing virtual tables");
-            smp::invoke_on_all([&] {
-                return db::initialize_virtual_tables(db, ss, gossiper, raft_gr, sys_ks, tablet_allocator, messaging, *cfg);
-            }).get();
+            db::initialize_virtual_tables(db, ss, gossiper, raft_gr, sys_ks, tablet_allocator, messaging, *cfg).get();
 
             // #293 - do not stop anything
             // engine().at_exit([&qp] { return qp.stop(); });
diff --git a/test/lib/cql_test_env.cc b/test/lib/cql_test_env.cc
index c8f93be45f..5742e6c40e 100644
--- a/test/lib/cql_test_env.cc
+++ b/test/lib/cql_test_env.cc
@@ -1008,9 +1008,7 @@ private:
                 _mnotifier.local().unregister_listener(&_ss.local()).get();
             });
 
-            smp::invoke_on_all([&] {
-                return db::initialize_virtual_tables(_db, _ss, _gossiper, _group0_registry, _sys_ks, _tablet_allocator, _ms, *cfg);
-            }).get();
+            db::initialize_virtual_tables(_db, _ss, _gossiper, _group0_registry, _sys_ks, _tablet_allocator, _ms, *cfg).get();
 
             _qp.invoke_on_all([this, &group0_client] (cql3::query_processor& qp) {
                 qp.start_remote(_mm.local(), _mapreduce_service.local(), _ss.local(), group0_client,