BatchCursor refactorings (#1246)

- Added SingleBatchCursor
- QueryResult and QueryBatchCursor renaming
   - Renamed and moved QueryResult to CommandCursorResult
   - Renamed QueryBatchCursor to CommandBatchCursor
   - Renamed AsyncQueryBatchCursor to AsyncCommandBatchCursor
- Unified Async & Sync CommandBatchCursor testing
- Added a CursorResourceManager for both Async & Sync

JAVA-5159

.evergreen/run-load-balancer-tests.sh

@@ -79,7 +79,8 @@ echo $second
   -Dorg.mongodb.test.uri=${SINGLE_MONGOS_LB_URI} \
   -Dorg.mongodb.test.multi.mongos.uri=${MULTI_MONGOS_LB_URI} \
   ${GRADLE_EXTRA_VARS} --stacktrace --info --continue driver-core:test \
-  --tests QueryBatchCursorFunctionalSpecification
+  --tests CommandBatchCursorFunctionalTest \
+  --tests AsyncCommandBatchCursorFunctionalTest
 third=$?
 echo $third
 

config/codenarc/codenarc.xml

@@ -34,12 +34,6 @@
         <exclude name="ComparisonWithSelf"/>
     </ruleset-ref>
     <ruleset-ref path='rulesets/braces.xml'/>
-    <ruleset-ref path='rulesets/concurrency.xml'>
-        <rule-config name='BusyWait'>
-            <property name='doNotApplyToFileNames' value='AsyncQueryBatchCursorFunctionalSpecification.groovy'/>
-        </rule-config>
-
-    </ruleset-ref>
     <ruleset-ref path='rulesets/convention.xml'>
         <rule-config name='NoDef'>
             <property name='doNotApplyToFilesMatching' value='.*Specification.groovy'/>

driver-core/src/main/com/mongodb/assertions/Assertions.java

@@ -21,6 +21,7 @@
 import com.mongodb.lang.Nullable;
 
 import java.util.Collection;
+import java.util.function.Supplier;
 
 /**
  * <p>Design by contract assertions.</p> <p>This class is not part of the public API and may be removed or changed at any time.</p>
@@ -226,6 +227,19 @@ public static AssertionError fail(final String msg) throws AssertionError {
         throw new AssertionError(assertNotNull(msg));
     }
 
+    /**
+     * @param supplier the supplier to check
+     * @return {@code supplier.get()}
+     * @throws AssertionError If {@code supplier.get()} throws an exception
+     */
+    public static <T> T doesNotThrow(final Supplier<T> supplier) throws AssertionError {
+        try {
+            return supplier.get();
+        } catch (Exception e) {
+            throw new AssertionError(e.getMessage(), e);
+        }
+    }
+
     private Assertions() {
     }
 }

driver-core/src/main/com/mongodb/internal/async/AsyncAggregateResponseBatchCursor.java

@@ -16,6 +16,7 @@
 
 package com.mongodb.internal.async;
 
+import com.mongodb.lang.Nullable;
 import org.bson.BsonDocument;
 import org.bson.BsonTimestamp;
 
@@ -25,8 +26,10 @@
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
 public interface AsyncAggregateResponseBatchCursor<T> extends AsyncBatchCursor<T> {
+    @Nullable
     BsonDocument getPostBatchResumeToken();
 
+    @Nullable
     BsonTimestamp getOperationTime();
 
     boolean isFirstBatchEmpty();

driver-core/src/main/com/mongodb/internal/async/AsyncBatchCursor.java

@@ -16,6 +16,8 @@
 
 package com.mongodb.internal.async;
 
+import com.mongodb.internal.operation.BatchCursor;
+
 import java.io.Closeable;
 import java.util.List;
 
@@ -28,9 +30,9 @@
  */
 public interface AsyncBatchCursor<T> extends Closeable {
     /**
-     * Returns the next batch of results.  A tailable cursor will block until another batch exists.  After the last batch, the next call
-     * to this method will execute the callback with a null result to indicate that there are no more batches available and the cursor
-     * has been closed.
+     * Returns the next batch of results. A tailable cursor will block until another batch exists.
+     * Unlike the {@link BatchCursor} this method will automatically mark the cursor as closed when there are no more expected results.
+     * Care should be taken to check {@link #isClosed()} between calls.
      *
      * @param callback callback to receive the next batch of results
      * @throws java.util.NoSuchElementException if no next batch exists

driver-core/src/main/com/mongodb/internal/operation/AggregateOperationImpl.java

@@ -18,13 +18,11 @@
 
 import com.mongodb.MongoNamespace;
 import com.mongodb.client.model.Collation;
-import com.mongodb.connection.ConnectionDescription;
 import com.mongodb.internal.async.AsyncBatchCursor;
 import com.mongodb.internal.async.SingleResultCallback;
 import com.mongodb.internal.binding.AsyncReadBinding;
 import com.mongodb.internal.binding.ReadBinding;
 import com.mongodb.internal.client.model.AggregationLevel;
-import com.mongodb.internal.connection.QueryResult;
 import com.mongodb.internal.session.SessionContext;
 import com.mongodb.lang.Nullable;
 import org.bson.BsonArray;
@@ -40,15 +38,13 @@
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
-import static com.mongodb.assertions.Assertions.assertNotNull;
 import static com.mongodb.assertions.Assertions.isTrueArgument;
 import static com.mongodb.assertions.Assertions.notNull;
 import static com.mongodb.internal.async.ErrorHandlingResultCallback.errorHandlingCallback;
 import static com.mongodb.internal.operation.AsyncOperationHelper.CommandReadTransformerAsync;
 import static com.mongodb.internal.operation.AsyncOperationHelper.executeRetryableReadAsync;
 import static com.mongodb.internal.operation.CommandOperationHelper.CommandCreator;
 import static com.mongodb.internal.operation.OperationHelper.LOGGER;
-import static com.mongodb.internal.operation.OperationHelper.cursorDocumentToQueryResult;
 import static com.mongodb.internal.operation.OperationReadConcernHelper.appendReadConcernToCommand;
 import static com.mongodb.internal.operation.SyncOperationHelper.CommandReadTransformer;
 import static com.mongodb.internal.operation.SyncOperationHelper.executeRetryableRead;
@@ -239,25 +235,16 @@ BsonDocument getCommand(final SessionContext sessionContext, final int maxWireVe
         return commandDocument;
     }
 
-    private QueryResult<T> createQueryResult(final BsonDocument result, final ConnectionDescription description) {
-        assertNotNull(result);
-        return cursorDocumentToQueryResult(result.getDocument(CURSOR), description.getServerAddress());
-    }
-
-    private CommandReadTransformer<BsonDocument, QueryBatchCursor<T>> transformer() {
-        return (result, source, connection) -> {
-            QueryResult<T> queryResult = createQueryResult(result, connection.getDescription());
-            return new QueryBatchCursor<>(queryResult, 0, batchSize != null ? batchSize : 0, maxAwaitTimeMS, decoder, comment,
-                    source, connection, result);
-        };
+    private CommandReadTransformer<BsonDocument, CommandBatchCursor<T>> transformer() {
+        return (result, source, connection) ->
+                new CommandBatchCursor<>(result, batchSize != null ? batchSize : 0, maxAwaitTimeMS, decoder,
+                        comment, source, connection);
     }
 
     private CommandReadTransformerAsync<BsonDocument, AsyncBatchCursor<T>> asyncTransformer() {
-        return (result, source, connection) -> {
-            QueryResult<T> queryResult = createQueryResult(result, connection.getDescription());
-            return new AsyncQueryBatchCursor<>(queryResult, 0, batchSize != null ? batchSize : 0, maxAwaitTimeMS, decoder,
-                    comment, source, connection, result);
-        };
+        return (result, source, connection) ->
+                new AsyncCommandBatchCursor<>(result, batchSize != null ? batchSize : 0, maxAwaitTimeMS, decoder,
+                        comment, source, connection);
     }
 
     interface AggregateTarget {

driver-core/src/main/com/mongodb/internal/operation/AggregateResponseBatchCursor.java

@@ -17,6 +17,7 @@
 package com.mongodb.internal.operation;
 
 import com.mongodb.annotations.NotThreadSafe;
+import com.mongodb.lang.Nullable;
 import org.bson.BsonDocument;
 import org.bson.BsonTimestamp;
 
@@ -27,8 +28,10 @@
  */
 @NotThreadSafe
 public interface AggregateResponseBatchCursor<T> extends BatchCursor<T> {
+    @Nullable
     BsonDocument getPostBatchResumeToken();
 
+    @Nullable
     BsonTimestamp getOperationTime();
 
     boolean isFirstBatchEmpty();

driver-core/src/main/com/mongodb/internal/operation/AsyncChangeStreamBatchCursor.java

@@ -18,6 +18,7 @@
 
 import com.mongodb.MongoException;
 import com.mongodb.internal.async.AsyncAggregateResponseBatchCursor;
+import com.mongodb.internal.async.AsyncBatchCursor;
 import com.mongodb.internal.async.SingleResultCallback;
 import com.mongodb.internal.binding.AsyncReadBinding;
 import com.mongodb.lang.NonNull;
@@ -50,11 +51,11 @@ final class AsyncChangeStreamBatchCursor<T> implements AsyncAggregateResponseBat
      * {@code wrapped} containing {@code null} and {@link #isClosed} being {@code false}.
      * This represents a situation in which the wrapped object was closed by {@code this} but {@code this} remained open.
      */
-    private final AtomicReference<AsyncAggregateResponseBatchCursor<RawBsonDocument>> wrapped;
+    private final AtomicReference<AsyncCommandBatchCursor<RawBsonDocument>> wrapped;
     private final AtomicBoolean isClosed;
 
     AsyncChangeStreamBatchCursor(final ChangeStreamOperation<T> changeStreamOperation,
-                                 final AsyncAggregateResponseBatchCursor<RawBsonDocument> wrapped,
+                                 final AsyncCommandBatchCursor<RawBsonDocument> wrapped,
                                  final AsyncReadBinding binding,
                                  @Nullable final BsonDocument resumeToken,
                                  final int maxWireVersion) {
@@ -68,13 +69,13 @@ final class AsyncChangeStreamBatchCursor<T> implements AsyncAggregateResponseBat
     }
 
     @NonNull
-    AsyncAggregateResponseBatchCursor<RawBsonDocument> getWrapped() {
+    AsyncCommandBatchCursor<RawBsonDocument> getWrapped() {
         return assertNotNull(wrapped.get());
     }
 
     @Override
     public void next(final SingleResultCallback<List<T>> callback) {
-        resumeableOperation((cursor, callback1) -> cursor.next(callback1), callback, false);
+        resumeableOperation(AsyncBatchCursor::next, callback, false);
     }
 
     @Override
@@ -129,15 +130,15 @@ private void nullifyAndCloseWrapped() {
 
     /**
      * This method guarantees that the {@code newValue} argument is closed even if
-     * {@link #setWrappedOrCloseIt(AsyncAggregateResponseBatchCursor)} is called concurrently with or after (in the happens-before order)
+     * {@code setWrappedOrCloseIt(AsyncCommandBatchCursor)} is called concurrently with or after (in the happens-before order)
      * the method {@link #close()}.
      */
-    private void setWrappedOrCloseIt(final AsyncAggregateResponseBatchCursor<RawBsonDocument> newValue) {
+    private void setWrappedOrCloseIt(final AsyncCommandBatchCursor<RawBsonDocument> newValue) {
         if (isClosed()) {
-            assertNull(this.wrapped.get());
+            assertNull(wrapped.get());
             newValue.close();
         } else {
-            assertNull(this.wrapped.getAndSet(newValue));
+            assertNull(wrapped.getAndSet(newValue));
             if (isClosed()) {
                 nullifyAndCloseWrapped();
             }
@@ -164,8 +165,8 @@ public int getMaxWireVersion() {
         return maxWireVersion;
     }
 
-    private void cachePostBatchResumeToken(final AsyncAggregateResponseBatchCursor<RawBsonDocument> queryBatchCursor) {
-        BsonDocument resumeToken = queryBatchCursor.getPostBatchResumeToken();
+    private void cachePostBatchResumeToken(final AsyncCommandBatchCursor<RawBsonDocument> cursor) {
+        BsonDocument resumeToken = cursor.getPostBatchResumeToken();
         if (resumeToken != null) {
             this.resumeToken = resumeToken;
         }
@@ -182,13 +183,13 @@ private void resumeableOperation(final AsyncBlock asyncBlock, final SingleResult
                     tryNext ? "tryNext()" : "next()")));
             return;
         }
-        AsyncAggregateResponseBatchCursor<RawBsonDocument> wrappedCursor = getWrapped();
+        AsyncCommandBatchCursor<RawBsonDocument> wrappedCursor = getWrapped();
         asyncBlock.apply(wrappedCursor, (result, t) -> {
             if (t == null) {
                 try {
                     List<T> convertedResults;
                     try {
-                        convertedResults = convertAndProduceLastId(result, changeStreamOperation.getDecoder(),
+                        convertedResults = convertAndProduceLastId(assertNotNull(result), changeStreamOperation.getDecoder(),
                                 lastId -> resumeToken = lastId);
                     } finally {
                         cachePostBatchResumeToken(wrappedCursor);
@@ -215,14 +216,15 @@ private void retryOperation(final AsyncBlock asyncBlock, final SingleResultCallb
             if (t != null) {
                 callback.onResult(null, t);
             } else {
-                changeStreamOperation.setChangeStreamOptionsForResume(resumeToken, source.getServerDescription().getMaxWireVersion());
+                changeStreamOperation.setChangeStreamOptionsForResume(resumeToken,
+                        assertNotNull(source).getServerDescription().getMaxWireVersion());
                 source.release();
                 changeStreamOperation.executeAsync(binding, (result, t1) -> {
                     if (t1 != null) {
                         callback.onResult(null, t1);
                     } else {
                         try {
-                            setWrappedOrCloseIt(((AsyncChangeStreamBatchCursor<T>) result).getWrapped());
+                            setWrappedOrCloseIt(assertNotNull((AsyncChangeStreamBatchCursor<T>) result).getWrapped());
                         } finally {
                             try {
                                 binding.release(); // release the new change stream batch cursor's reference to the binding