storage_service: Serialize is_joined with read api lock

api/storage_service.cc

@@ -495,8 +495,10 @@ void set_storage_service(http_context& ctx, routes& r) {
         });
     });
 
-    ss::is_joined.set(r, [](const_req req) {
-        return service::get_local_storage_service().is_joined();
+    ss::is_joined.set(r, [] (std::unique_ptr<request> req) {
+        return service::get_local_storage_service().is_joined().then([] (bool is_joined) {
+            return make_ready_future<json::json_return_type>(is_joined);
+        });
     });
 
     ss::set_stream_throughput_mb_per_sec.set(r, [](std::unique_ptr<request> req) {

service/storage_service.cc

@@ -379,6 +379,13 @@ future<> storage_service::join_ring() {
     });
 }
 
+future<bool> storage_service::is_joined() {
+    return run_with_read_api_lock([] (storage_service& ss) {
+        return ss._joined;
+    });
+}
+
+
 // Runs inside seastar::async context
 void storage_service::bootstrap(std::unordered_set<token> tokens) {
     _is_bootstrap_mode = true;

service/storage_service.hh

@@ -361,9 +361,7 @@ private:
     void join_token_ring(int delay);
 public:
     future<> join_ring();
-    bool is_joined() {
-        return _joined;
-    }
+    future<bool> is_joined();
 
     future<> rebuild(sstring source_dc);