Set connection mode to MULTIPLE when srvHost is specified in ClusterSettings

Also:

* Fix the check that the srvHost has three parts
* Throw exception if the mode is not compatible with SRV
* Beef up the unit tests for SRV in ClusterSettings

JAVA-3573

Author: jyemin

driver-core/src/main/com/mongodb/connection/ClusterSettings.java

@@ -17,7 +17,6 @@
 package com.mongodb.connection;
 
 import com.mongodb.ConnectionString;
-import com.mongodb.MongoClientException;
 import com.mongodb.MongoClientSettings;
 import com.mongodb.ServerAddress;
 import com.mongodb.annotations.Immutable;
@@ -596,14 +595,13 @@ public String getShortDescription() {
     }
 
     private ClusterSettings(final Builder builder) {
-        // TODO: Unit test this
         if (builder.srvHost != null) {
             if (builder.srvHost.contains(":")) {
                 throw new IllegalArgumentException("The srvHost can not contain a host name that specifies a port");
             }
 
-            if (builder.hosts.get(0).getHost().split("\\.").length < 3) {
-                throw new MongoClientException(format("An SRV host name '%s' was provided that does not contain at least three parts. "
+            if (builder.srvHost.split("\\.").length < 3) {
+                throw new IllegalArgumentException(format("An SRV host name '%s' was provided that does not contain at least three parts. "
                         + "It must contain a hostname, domain name and a top level domain.", builder.hosts.get(0).getHost()));
             }
         }
@@ -612,10 +610,6 @@ private ClusterSettings(final Builder builder) {
             throw new IllegalArgumentException("Multiple hosts cannot be specified when using ClusterType.STANDALONE.");
         }
 
-        if (builder.mode != null && builder.mode == ClusterConnectionMode.SINGLE && builder.hosts.size() > 1) {
-            throw new IllegalArgumentException("Can not directly connect to more than one server");
-        }
-
         if (builder.requiredReplicaSetName != null) {
             if (builder.requiredClusterType == ClusterType.UNKNOWN) {
                 builder.requiredClusterType = ClusterType.REPLICA_SET;
@@ -628,7 +622,18 @@ private ClusterSettings(final Builder builder) {
         description = builder.description;
         srvHost = builder.srvHost;
         hosts = builder.hosts;
-        mode = builder.mode != null ? builder.mode : hosts.size() == 1 ? ClusterConnectionMode.SINGLE : ClusterConnectionMode.MULTIPLE;
+        if (srvHost != null) {
+            if (builder.mode == ClusterConnectionMode.SINGLE) {
+                throw new IllegalArgumentException("An SRV host name was provided but the connection mode is not MULTIPLE");
+            }
+            mode = ClusterConnectionMode.MULTIPLE;
+        } else {
+            if (builder.mode == ClusterConnectionMode.SINGLE && builder.hosts.size() > 1) {
+                throw new IllegalArgumentException("Can not directly connect to more than one server");
+            }
+
+            mode = builder.mode != null ? builder.mode : hosts.size() == 1 ? ClusterConnectionMode.SINGLE : ClusterConnectionMode.MULTIPLE;
+        }
         requiredReplicaSetName = builder.requiredReplicaSetName;
         requiredClusterType = builder.requiredClusterType;
         localThresholdMS = builder.localThresholdMS;

driver-core/src/test/unit/com/mongodb/connection/ClusterSettingsSpecification.groovy

@@ -28,7 +28,6 @@ import spock.lang.Specification
 
 import java.util.concurrent.TimeUnit
 
-// TODO: add SRV tests
 class ClusterSettingsSpecification extends Specification {
     def hosts = [new ServerAddress('localhost'), new ServerAddress('localhost', 30000)]
     def serverSelector = new WritableServerSelector()
@@ -105,6 +104,48 @@ class ClusterSettingsSpecification extends Specification {
         ClusterSettings.builder(customSettings).applySettings(defaultSettings).build() == defaultSettings
     }
 
+    def 'when hosts contains more than one element and mode is SINGLE, should throw IllegalArgumentException'() {
+        when:
+        def builder = ClusterSettings.builder()
+        builder.hosts([new ServerAddress('host1'), new ServerAddress('host2')])
+        builder.mode(ClusterConnectionMode.SINGLE)
+        builder.build()
+
+        then:
+        thrown(IllegalArgumentException)
+    }
+
+    def 'when srvHost is specified, should set mode to MULTIPLE'() {
+        when:
+        def builder = ClusterSettings.builder()
+        builder.srvHost('foo.bar.com')
+        def settings = builder.build()
+
+        then:
+        settings.getSrvHost() == 'foo.bar.com'
+        settings.getMode() == ClusterConnectionMode.MULTIPLE
+    }
+
+    def 'when srvHost contains a colon, should throw IllegalArgumentException'() {
+        when:
+        def builder = ClusterSettings.builder()
+        builder.srvHost('foo.bar.com:27017')
+        builder.build()
+
+        then:
+        thrown(IllegalArgumentException)
+    }
+
+    def 'when srvHost contains less than three parts (host, domain, top-level domain, should throw IllegalArgumentException'() {
+        when:
+        def builder = ClusterSettings.builder()
+        builder.srvHost('foo.bar')
+        builder.build()
+
+        then:
+        thrown(IllegalArgumentException)
+    }
+
     def 'should allow configure serverSelectors correctly'() {
         given:
         def latMinServerSelector = new LatencyMinimizingServerSelector(10, TimeUnit.MILLISECONDS)