GODRIVER-3054 Handshake connection should not use legacy for LB

Makefile

@@ -153,6 +153,7 @@ evg-test-load-balancers:
 	go test $(BUILD_TAGS) ./mongo/integration -run TestChangeStreamSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
 	go test $(BUILD_TAGS) ./mongo/integration -run TestInitialDNSSeedlistDiscoverySpec/load_balanced -v -timeout $(TEST_TIMEOUT)s >> test.suite
 	go test $(BUILD_TAGS) ./mongo/integration -run TestLoadBalancerSupport -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestLoadBalancedConnectionHandshake -v -timeout $(TEST_TIMEOUT)s >> test.suite
 	go test $(BUILD_TAGS) ./mongo/integration/unified -run TestUnifiedSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
 
 .PHONY: evg-test-search-index

mongo/integration/client_test.go

@@ -768,27 +768,6 @@ func TestClient(t *testing.T) {
 				"expected 'OP_MSG' OpCode in wire message, got %q", pair.Sent.OpCode.String())
 		}
 	})
-
-	// Test that OP_MSG is used for handshakes when loadBalanced is true.
-	opMsgLBOpts := mtest.NewOptions().ClientType(mtest.Proxy).MinServerVersion("5.0").Topologies(mtest.LoadBalanced)
-	mt.RunOpts("OP_MSG used for handshakes when loadBalanced is true", opMsgLBOpts, func(mt *mtest.T) {
-		err := mt.Client.Ping(context.Background(), mtest.PrimaryRp)
-		assert.Nil(mt, err, "Ping error: %v", err)
-
-		msgPairs := mt.GetProxiedMessages()
-		assert.True(mt, len(msgPairs) >= 3, "expected at least 3 events, got %v", len(msgPairs))
-
-		// First three messages should be connection handshakes: one for the heartbeat connection, another for the
-		// application connection, and a final one for the RTT monitor connection.
-		for idx, pair := range msgPairs[:3] {
-			assert.Equal(mt, "hello", pair.CommandName, "expected command name 'hello' at index %d, got %s", idx,
-				pair.CommandName)
-
-			// Assert that appended OpCode is OP_MSG when loadBalanced is true.
-			assert.Equal(mt, wiremessage.OpMsg, pair.Sent.OpCode,
-				"expected 'OP_MSG' OpCode in wire message, got %q", pair.Sent.OpCode.String())
-		}
-	})
 }
 
 func TestClient_BSONOptions(t *testing.T) {

mongo/integration/handshake_test.go

@@ -20,6 +20,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/integration/mtest"
 	"go.mongodb.org/mongo-driver/version"
 	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+	"go.mongodb.org/mongo-driver/x/mongo/driver/wiremessage"
 )
 
 func TestHandshakeProse(t *testing.T) {
@@ -199,3 +200,53 @@ func TestHandshakeProse(t *testing.T) {
 		})
 	}
 }
+
+func TestLoadBalancedConnectionHandshake(t *testing.T) {
+	mt := mtest.New(t)
+
+	lbopts := mtest.NewOptions().ClientType(mtest.Proxy).Topologies(
+		mtest.LoadBalanced)
+
+	mt.RunOpts("LB connection handshake uses OP_MSG", lbopts, func(mt *mtest.T) {
+		// Ping the server to ensure the handshake has completed.
+		err := mt.Client.Ping(context.Background(), nil)
+		require.NoError(mt, err, "Ping error: %v", err)
+
+		messages := mt.GetProxiedMessages()
+		handshakeMessage := messages[:1][0]
+
+		// Per the specifications, if loadBalanced=true, drivers MUST use the hello
+		// command for the initial handshake and use the OP_MSG protocol.
+		assert.Equal(mt, "hello", handshakeMessage.CommandName)
+		assert.Equal(mt, wiremessage.OpMsg, handshakeMessage.Sent.OpCode)
+	})
+
+	opts := mtest.NewOptions().ClientType(mtest.Proxy).Topologies(
+		mtest.ReplicaSet,
+		mtest.Sharded,
+		mtest.Single,
+		mtest.ShardedReplicaSet)
+
+	mt.RunOpts("non-LB connection handshake uses OP_QUERY", opts, func(mt *mtest.T) {
+		// Ping the server to ensure the handshake has completed.
+		err := mt.Client.Ping(context.Background(), nil)
+		require.NoError(mt, err, "Ping error: %v", err)
+
+		messages := mt.GetProxiedMessages()
+		handshakeMessage := messages[:1][0]
+
+		want := wiremessage.OpQuery
+
+		hello := handshake.LegacyHello
+		if os.Getenv("REQUIRE_API_VERSION") == "true" {
+			hello = "hello"
+
+			// If the server API version is requested, then we should use OP_MSG
+			// regardless of the topology
+			want = wiremessage.OpMsg
+		}
+
+		assert.Equal(mt, hello, handshakeMessage.CommandName)
+		assert.Equal(mt, want, handshakeMessage.Sent.OpCode)
+	})
+}

testdata/load-balancers/sdam-error-handling.json

@@ -279,7 +279,8 @@
               },
               "data": {
                 "failCommands": [
-                  "isMaster"
+                  "isMaster",
+                  "hello"
                 ],
                 "closeConnection": true,
                 "appName": "lbSDAMErrorTestClient"

testdata/load-balancers/sdam-error-handling.yml

@@ -153,7 +153,7 @@ tests:
             configureFailPoint: failCommand
             mode: { times: 1 }
             data:
-              failCommands: [isMaster]
+              failCommands: [isMaster, hello]
               closeConnection: true
               appName: *singleClientAppName
       - name: insertOne

x/mongo/driver/operation/hello.go

@@ -530,7 +530,7 @@ func (h *Hello) handshakeCommand(dst []byte, desc description.SelectedServer) ([
 func (h *Hello) command(dst []byte, desc description.SelectedServer) ([]byte, error) {
 	// Use "hello" if topology is LoadBalanced, API version is declared or server
 	// has responded with "helloOk". Otherwise, use legacy hello.
-	if desc.Kind == description.LoadBalanced || h.serverAPI != nil || desc.Server.HelloOK {
+	if h.loadBalanced || h.serverAPI != nil || desc.Server.HelloOK {
 		dst = bsoncore.AppendInt32Element(dst, "hello", 1)
 	} else {
 		dst = bsoncore.AppendInt32Element(dst, handshake.LegacyHello, 1)
@@ -575,8 +575,8 @@ func (h *Hello) StreamResponse(ctx context.Context, conn driver.StreamerConnecti
 // loadBalanced is False. If this is the case, then the drivers MUST use legacy
 // hello for the first message of the initial handshake with the OP_QUERY
 // protocol
-func isLegacyHandshake(srvAPI *driver.ServerAPIOptions, deployment driver.Deployment) bool {
-	return srvAPI == nil && deployment.Kind() != description.LoadBalanced
+func isLegacyHandshake(srvAPI *driver.ServerAPIOptions, loadbalanced bool) bool {
+	return srvAPI == nil && !loadbalanced
 }
 
 func (h *Hello) createOperation() driver.Operation {
@@ -592,7 +592,7 @@ func (h *Hello) createOperation() driver.Operation {
 		ServerAPI: h.serverAPI,
 	}
 
-	if isLegacyHandshake(h.serverAPI, h.d) {
+	if isLegacyHandshake(h.serverAPI, h.loadBalanced) {
 		op.Legacy = driver.LegacyHandshake
 	}
 
@@ -616,7 +616,7 @@ func (h *Hello) GetHandshakeInformation(ctx context.Context, _ address.Address,
 		ServerAPI: h.serverAPI,
 	}
 
-	if isLegacyHandshake(h.serverAPI, deployment) {
+	if isLegacyHandshake(h.serverAPI, h.loadBalanced) {
 		op.Legacy = driver.LegacyHandshake
 	}