view_update_generator: Register staging sstables in constructor

First, it's to fix the discarded future during the register. The
future is not actually such, as it's always the no-op ready one as
at that stage the view_update_generator is neither aborted nor is
in throttling state.

Second, this change is to keep database start-up code in main
shorter and cleaner. Registering staging sstables belongs to the
view_update_generator start code.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

db/view/view_update_generator.cc

@@ -25,6 +25,7 @@
 #include "service/priority_manager.hh"
 #include "utils/error_injection.hh"
 #include "db/view/view_updating_consumer.hh"
+#include "sstables/sstables.hh"
 
 static logging::logger vug_logger("view_update_generator");
 
@@ -181,4 +182,18 @@ void view_update_generator::setup_metrics() {
     });
 }
 
+void view_update_generator::discover_staging_sstables() {
+    for (auto& x : _db.get_column_families()) {
+        table& t = *(x.second);
+        for (auto sstables = t.get_sstables(); sstables::shared_sstable sst : *sstables) {
+            if (sst->requires_view_building()) {
+                _sstables_with_tables[t.shared_from_this()].push_back(std::move(sst));
+                // we're at early stage here, no need to kick _pending_sstables (the
+                // bulding fiber is not running), neither we can wait on the semaphore
+                _registration_sem.consume(1);
+            }
+        }
+    }
+}
+
 }

db/view/view_update_generator.hh

@@ -46,6 +46,7 @@ private:
 public:
     view_update_generator(database& db) : _db(db) {
         setup_metrics();
+        discover_staging_sstables();
     }
 
     future<> start();
@@ -56,6 +57,7 @@ public:
 private:
     bool should_throttle() const;
     void setup_metrics();
+    void discover_staging_sstables();
 };
 
 }

main.cc

@@ -997,18 +997,6 @@ int main(int ac, char** av) {
 
             supervisor::notify("starting view update generator");
             view_update_generator.start(std::ref(db)).get();
-            supervisor::notify("discovering staging sstables");
-            db.invoke_on_all([] (database& db) {
-                for (auto& x : db.get_column_families()) {
-                    table& t = *(x.second);
-                    for (auto sstables = t.get_sstables(); sstables::shared_sstable sst : *sstables) {
-                        if (sst->requires_view_building()) {
-                            // FIXME: discarded future.
-                            (void)view_update_generator.local().register_staging_sstable(std::move(sst), t.shared_from_this());
-                        }
-                    }
-                }
-            }).get();
 
             supervisor::notify("setting up system keyspace");
             db::system_keyspace::setup(db, qp, feature_service, messaging).get();