Throw MongoClientException for sharded cluster transactions

This version of the driver does not support sharded cluster
transactions, so should throw a MongoClientException it an application
attempts it.

JAVA-3240

Author: jyemin

driver-async/src/test/functional/com/mongodb/async/client/TransactionFailureTest.java

@@ -33,12 +33,23 @@ public TransactionFailureTest() {
 
     @Before
     public void setUp() {
-        assumeTrue(canRunTests());
         super.setUp();
     }
 
     @Test(expected = MongoClientException.class)
-    public void testTransactionFails() throws InterruptedException {
+    public void testTransactionFailsOn40Cluster() throws InterruptedException {
+        assumeTrue(serverVersionLessThan("4.0"));
+        doTransaction();
+    }
+
+    @Test(expected = MongoClientException.class)
+    public void testTransactionFailsOnShardedCluster() throws InterruptedException {
+        assumeTrue(isSharded());
+        doTransaction();
+    }
+
+
+    private void doTransaction() throws InterruptedException {
         final ClientSession clientSession = createSession();
 
         try {
@@ -61,10 +72,4 @@ public void execute() {
             }
         }.get();
     }
-
-
-    private boolean canRunTests() {
-        return serverVersionLessThan("4.0")
-                || (serverVersionLessThan("4.1.0") && isSharded());
-    }
 }

driver-core/src/main/com/mongodb/internal/connection/CommandMessage.java

@@ -50,7 +50,6 @@
 import static com.mongodb.connection.ServerType.SHARD_ROUTER;
 import static com.mongodb.internal.connection.BsonWriterHelper.writePayload;
 import static com.mongodb.internal.connection.ReadConcernHelper.getReadConcernDocument;
-import static com.mongodb.internal.operation.ServerVersionHelper.FOUR_DOT_TWO_WIRE_VERSION;
 import static com.mongodb.internal.operation.ServerVersionHelper.FOUR_DOT_ZERO_WIRE_VERSION;
 import static com.mongodb.internal.operation.ServerVersionHelper.THREE_DOT_SIX_WIRE_VERSION;
 
@@ -265,9 +264,10 @@ private List<BsonElement> getExtraElements(final SessionContext sessionContext)
 
     private void checkServerVersionForTransactionSupport() {
         int wireVersion = getSettings().getMaxWireVersion();
-        if (wireVersion < FOUR_DOT_ZERO_WIRE_VERSION
-                || (wireVersion < FOUR_DOT_TWO_WIRE_VERSION && getSettings().getServerType() == SHARD_ROUTER)) {
+        if (wireVersion < FOUR_DOT_ZERO_WIRE_VERSION) {
             throw new MongoClientException("Transactions are not supported by the MongoDB cluster to which this client is connected.");
+        } else if (getSettings().getServerType() == SHARD_ROUTER) {
+            throw new MongoClientException("This version of the driver does not support transactions on a sharded cluster.");
         }
     }
 

driver-sync/src/test/functional/com/mongodb/client/TransactionFailureTest.java

@@ -31,12 +31,22 @@ public TransactionFailureTest() {
 
     @Before
     public void setUp() {
-        assumeTrue(canRunTests());
         super.setUp();
     }
 
     @Test(expected = MongoClientException.class)
-    public void testTransactionFails() {
+    public void testTransactionFailsOn40Cluster() {
+        assumeTrue(serverVersionLessThan("4.0"));
+        doTransaction();
+    }
+
+    @Test(expected = MongoClientException.class)
+    public void testTransactionFailsOnShardedCluster() {
+        assumeTrue(isSharded());
+        doTransaction();
+    }
+
+    private void doTransaction() {
         ClientSession clientSession = client.startSession();
         try {
             clientSession.startTransaction();
@@ -45,9 +55,4 @@ public void testTransactionFails() {
             clientSession.close();
         }
     }
-
-    private boolean canRunTests() {
-        return serverVersionLessThan("4.0")
-                || (serverVersionLessThan("4.1.0") && isSharded());
-    }
 }