SERVER-57136 Skip maxStaleness wire version check when server is down.

(cherry picked from commit d7bd51c05a7ac49afd7ed3b394fde123383af6de)

3 files changed, 45 insertions, 13 deletions

diff --git a/src/mongo/client/sdam/server_selection_json_test_runner.cpp b/src/mongo/client/sdam/server_selection_json_test_runner.cpp
index cc1e50d28b1..72379e27165 100644
--- a/src/mongo/client/sdam/server_selection_json_test_runner.cpp
+++ b/src/mongo/client/sdam/server_selection_json_test_runner.cpp
@@ -387,18 +387,19 @@ private:
                                         setName);
         _topologyDescription = std::make_shared<TopologyDescription>(config);
 
-        if (_jsonTest.hasField("in_latency_window")) {
-            const std::vector<BSONElement>& bsonLatencyWindow =
-                _jsonTest["in_latency_window"].Array();
-            for (const auto& serverDescription : serverDescriptions) {
-                _topologyDescription->installServerDescription(serverDescription);
-
-                for (auto bsonServer : bsonLatencyWindow) {
-                    auto server = bsonServer.Obj();
-                    if (serverDescription->getAddress() ==
-                        HostAndPort(server.getStringField("address"))) {
-                        _inLatencyWindow.push_back(serverDescription);
-                    }
+        std::vector<BSONElement> bsonLatencyWindow;
+        if (auto inLatencyWindowElem = _jsonTest["in_latency_window"]) {
+            bsonLatencyWindow = inLatencyWindowElem.Array();
+        }
+
+        for (const auto& serverDescription : serverDescriptions) {
+            _topologyDescription->installServerDescription(serverDescription);
+
+            for (auto bsonServer : bsonLatencyWindow) {
+                auto server = bsonServer.Obj();
+                if (serverDescription->getAddress() ==
+                    HostAndPort(server.getStringField("address"))) {
+                    _inLatencyWindow.push_back(serverDescription);
                 }
             }
         }
diff --git a/src/mongo/client/sdam/server_selector.cpp b/src/mongo/client/sdam/server_selector.cpp
index 1b24550cea0..5dd58d95684 100644
--- a/src/mongo/client/sdam/server_selector.cpp
+++ b/src/mongo/client/sdam/server_selector.cpp
@@ -303,7 +303,8 @@ void SdamServerSelector::_verifyMaxstalenessWireVersions(TopologyDescriptionPtr
     for (auto& server : topologyDescription->getServers()) {
         uassert(ErrorCodes::IncompatibleServerVersion,
                 "Incompatible wire version",
-                server->getMaxWireVersion() >= WireVersion::COMMANDS_ACCEPT_WRITE_CONCERN);
+                server->getType() == ServerType::kUnknown ||
+                    server->getMaxWireVersion() >= WireVersion::COMMANDS_ACCEPT_WRITE_CONCERN);
     }
 }
 
diff --git a/src/mongo/client/sdam/server_selector_test.cpp b/src/mongo/client/sdam/server_selector_test.cpp
index 05dfd382904..6287123c8be 100644
--- a/src/mongo/client/sdam/server_selector_test.cpp
+++ b/src/mongo/client/sdam/server_selector_test.cpp
@@ -177,6 +177,36 @@ TEST_F(ServerSelectorTestFixture, ShouldThrowOnWireError) {
                        ErrorCodes::IncompatibleServerVersion);
 }
 
+TEST_F(ServerSelectorTestFixture, ShouldNotThrowWireErrorIfOnlyOneServerUnknown) {
+    TopologyStateMachine stateMachine(sdamConfiguration);
+    auto topologyDescription = std::make_shared<TopologyDescription>(sdamConfiguration);
+    auto primary = ServerDescriptionBuilder()
+                       .withAddress(HostAndPort("s0"))
+                       .withType(ServerType::kRSPrimary)
+                       .withLastUpdateTime(Date_t::now())
+                       .withLastWriteDate(Date_t::now())
+                       .withRtt(Milliseconds{1})
+                       .withSetName("set")
+                       .withHost(HostAndPort("s0"))
+                       .withHost(HostAndPort("s1"))
+                       .withMinWireVersion(WireVersion::SUPPORTS_OP_MSG)
+                       .withMaxWireVersion(WireVersion::LATEST_WIRE_VERSION)
+                       .instance();
+    stateMachine.onServerDescription(*topologyDescription, primary);
+
+    auto downedServer = ServerDescriptionBuilder().withAddress(HostAndPort("s1")).instance();
+    stateMachine.onServerDescription(*topologyDescription, downedServer);
+
+    ASSERT(topologyDescription->isWireVersionCompatible());
+
+    const auto ninetySeconds = Seconds(90);
+    const auto readPref =
+        ReadPreferenceSetting(ReadPreference::Nearest, TagSets::emptySet, ninetySeconds);
+    auto result = selector.selectServers(topologyDescription, readPref);
+    ASSERT(result);
+    ASSERT_EQ(primary->getAddress(), (*result)[0]->getAddress());
+}
+
 TEST_F(ServerSelectorTestFixture, ShouldReturnNoneIfTopologyUnknown) {
     auto topologyDescription = std::make_shared<TopologyDescription>(sdamConfiguration);
     ASSERT_EQ(TopologyType::kUnknown, topologyDescription->getType());