JAVA-2821: When killing a cursor, exceptions are supposed to be suppressed. The suppression now includes the attempt to get a connection on which to kill the cursor, which may also fail (e.g. if the server has been killed)

Author: jyemin

driver-core/src/main/com/mongodb/operation/QueryBatchCursor.java

@@ -277,13 +277,15 @@ private boolean limitReached() {
 
     private void killCursor() {
         if (serverCursor != null) {
-            Connection connection = connectionSource.getConnection();
             try {
-                killCursor(connection);
+                Connection connection = connectionSource.getConnection();
+                try {
+                    killCursor(connection);
+                } finally {
+                    connection.release();
+                }
             } catch (MongoException e) {
                 // Ignore exceptions from calling killCursor
-            } finally {
-                connection.release();
             }
         }
     }

driver-core/src/test/unit/com/mongodb/operation/QueryBatchCursorSpecification.groovy

@@ -18,6 +18,7 @@ package com.mongodb.operation
 
 import com.mongodb.MongoNamespace
 import com.mongodb.MongoSocketException
+import com.mongodb.MongoSocketOpenException
 import com.mongodb.ServerAddress
 import com.mongodb.binding.ConnectionSource
 import com.mongodb.connection.Connection
@@ -115,4 +116,30 @@ class QueryBatchCursorSpecification extends Specification {
         then:
         notThrown(Exception)
     }
+
+    def 'should handle exceptions when killing cursor and a connection can not be obtained'() {
+        given:
+        def serverAddress = new ServerAddress()
+        def connection = Mock(Connection)
+        def connectionSource = Stub(ConnectionSource) {
+            getConnection() >> { throw new MongoSocketOpenException("can't open socket", serverAddress, new IOException()) }
+        }
+        connectionSource.retain() >> connectionSource
+
+        def namespace = new MongoNamespace('test', 'QueryBatchCursorSpecification')
+        def firstBatch = new QueryResult(namespace, [], 42, serverAddress)
+        def cursor = new QueryBatchCursor<Document>(firstBatch, 0, 2, 100, new BsonDocumentCodec(), connectionSource, connection)
+
+        when:
+        cursor.close()
+
+        then:
+        notThrown(MongoSocketException)
+
+        when:
+        cursor.close()
+
+        then:
+        notThrown(Exception)
+    }
 }