JAVA-2683: Don't include a session identifier for unacknowledged write commands

Author: jyemin

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

@@ -200,7 +200,7 @@ private List<BsonElement> getExtraElements(final SessionContext sessionContext)
         if (sessionContext.getClusterTime() != null) {
             extraElements.add(new BsonElement("$clusterTime", sessionContext.getClusterTime()));
         }
-        if (sessionContext.hasSession()) {
+        if (sessionContext.hasSession() && responseExpected) {
             extraElements.add(new BsonElement("lsid", sessionContext.getSessionId()));
         }
         if (!isDefaultReadPreference(getReadPreference())) {

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

@@ -47,7 +47,8 @@ class CommandMessageSpecification extends Specification {
     def 'should encode command message with OP_MSG'() {
         given:
         def message = new CommandMessage(namespace, command, fieldNameValidator, readPreference,
-                MessageSettings.builder().serverVersion(new ServerVersion(3, 6)).build())
+                MessageSettings.builder().serverVersion(new ServerVersion(3, 6)).build(),
+                responseExpected, null, null)
         def output = new BasicOutputBuffer()
 
         when:
@@ -66,7 +67,7 @@ class CommandMessageSpecification extends Specification {
         if (sessionContext.clusterTime != null) {
             expectedCommandDocument.append('$clusterTime', sessionContext.clusterTime)
         }
-        if (sessionContext.hasSession()) {
+        if (sessionContext.hasSession() && responseExpected) {
             expectedCommandDocument.append('lsid', sessionContext.sessionId)
         }
 
@@ -76,7 +77,7 @@ class CommandMessageSpecification extends Specification {
         getCommandDocument(byteBuf, messageHeader) == expectedCommandDocument
 
         where:
-        [readPreference, sessionContext] << [
+        [readPreference, sessionContext, responseExpected] << [
                 [ReadPreference.primary(), ReadPreference.secondary()],
                 [
                         Stub(SessionContext) {
@@ -98,7 +99,8 @@ class CommandMessageSpecification extends Specification {
                             getClusterTime() >> new BsonDocument('clusterTime', new BsonTimestamp(42, 1))
                             getSessionId() >> new BsonDocument('id', new BsonBinary([1, 2, 3] as byte[]))
                         }
-                ]
+                ],
+                [true, false]
         ].combinations()
     }
 

driver/src/test/functional/com/mongodb/MongoClientSessionSpecification.groovy

@@ -323,11 +323,33 @@ class MongoClientSessionSpecification extends FunctionalSpecification {
         client.getDatabase('admin').runCommand(new BsonDocument('ping', new BsonInt32(1)))
 
         then:
-        def pingCommandStartedEvent = commandListener.events.get(0)
-        !(pingCommandStartedEvent as CommandStartedEvent).command.containsKey('lsid')
+        def pingCommandStartedEvent = commandListener.events.get(0) as CommandStartedEvent
+        !pingCommandStartedEvent.command.containsKey('lsid')
 
         cleanup:
         Fixture.getMongoClient().getDB('admin').removeUser(sessionTestUserName)
         client?.close()
     }
+
+    @IgnoreIf({ !serverVersionAtLeast(3, 6) })
+    def 'should not use a session for an unacknowledged write'() {
+        given:
+        def commandListener = new TestCommandListener()
+        def optionsBuilder = MongoClientOptions.builder()
+                .addCommandListener(commandListener)
+        def mongoClientURI = getMongoClientURI(optionsBuilder)
+        def client = new MongoClient(mongoClientURI)
+
+        when:
+        client.getDatabase(getDatabaseName()).getCollection(getCollectionName())
+                .withWriteConcern(WriteConcern.UNACKNOWLEDGED)
+                .insertOne(new Document())
+
+        then:
+        def insertEvent = commandListener.events.get(0) as CommandStartedEvent
+        !insertEvent.command.containsKey('lsid')
+
+        cleanup:
+        client?.close()
+    }
 }