Ignore seed name resolution errors on restart.

Gossiper seeds host name resolution failures are ignored during restart if
a node is already boostrapped (i.e. it has successfully joined the cluster).

Fixes scylladb/scylladb#14945

init.cc

@@ -16,7 +16,9 @@
 
 logging::logger startlog("init");
 
-std::set<gms::inet_address> get_seeds_from_db_config(const db::config& cfg, gms::inet_address broadcast_address) {
+std::set<gms::inet_address> get_seeds_from_db_config(const db::config& cfg,
+                                                     const gms::inet_address broadcast_address,
+                                                     const bool fail_on_lookup_error) {
     auto preferred = cfg.listen_interface_prefer_ipv6() ? std::make_optional(net::inet_address::family::INET6) : std::nullopt;
     auto family = cfg.enable_ipv6_dns_lookup() || preferred ? std::nullopt : std::make_optional(net::inet_address::family::INET);
     const auto listen = gms::inet_address::lookup(cfg.listen_address(), family).get();
@@ -32,8 +34,13 @@ std::set<gms::inet_address> get_seeds_from_db_config(const db::config& cfg, gms:
             try {
                 seeds.emplace(gms::inet_address::lookup(seed, family, preferred).get());
             } catch (...) {
-                startlog.error("Bad configuration: invalid value in 'seeds': '{}': {}", seed, std::current_exception());
-                throw bad_configuration_error();
+                if (fail_on_lookup_error) {
+                    startlog.error("Bad configuration: invalid value in 'seeds': '{}': {}", seed, std::current_exception());
+                    throw bad_configuration_error();
+                }
+                startlog.warn("Bad configuration: invalid value in 'seeds': '{}': {}. Node will continue booting since already bootstrapped.",
+                               seed,
+                               std::current_exception());
             }
             begin = next+1;
         }

init.hh

@@ -35,7 +35,9 @@ extern logging::logger startlog;
 
 class bad_configuration_error : public std::exception {};
 
-std::set<gms::inet_address> get_seeds_from_db_config(const db::config& cfg, gms::inet_address broadcast_address);
+[[nodiscard]] std::set<gms::inet_address> get_seeds_from_db_config(const db::config& cfg,
+                                                                   gms::inet_address broadcast_address,
+                                                                   bool fail_on_lookup_error);
 
 class service_set {
 public:

main.cc

@@ -1422,7 +1422,11 @@ To start the scylla server proper, simply invoke as: scylla server (or just scyl
                 startlog.warn("Using default cluster name is not recommended. Using a unique cluster name will reduce the chance of adding nodes to the wrong cluster by mistake");
             }
             auto group0_id = sys_ks.local().get_raft_group0_id().get();
-            auto gossiper_seeds = get_seeds_from_db_config(*cfg, broadcast_addr);
+
+            // Fail on a gossiper seeds lookup error only if the node is not bootstrapped.
+            const bool fail_on_lookup_error = !sys_ks.local().bootstrap_complete();
+
+            auto gossiper_seeds = get_seeds_from_db_config(*cfg, broadcast_addr, fail_on_lookup_error);
 
             auto get_gossiper_cfg = sharded_parameter([&] {
                 gms::gossip_config gcfg;

test/topology/test_start_bootstrapped_with_invalid_seed.py

@@ -13,8 +13,8 @@ from test.pylib.manager_client import ManagerClient
 
 logger = logging.getLogger(__name__)
 
+
 @pytest.mark.asyncio
-@pytest.mark.xfail(reason="issue #14945")
 async def test_start_bootstrapped_with_invalid_seed(manager: ManagerClient):
     """
     Issue https://github.com/scylladb/scylladb/issues/14945.