SERVER-18765 ClusterClientCursor and AsyncClusterClientCursor

1 files changed, 91 insertions, 0 deletions

diff --git a/src/mongo/s/query/cluster_client_cursor.h b/src/mongo/s/query/cluster_client_cursor.h
new file mode 100644
index 00000000000..e2ea3a72e59
--- /dev/null
+++ b/src/mongo/s/query/cluster_client_cursor.h
@@ -0,0 +1,91 @@
+/**
+ *    Copyright (C) 2015 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <boost/optional.hpp>
+
+#include "mongo/base/status_with.h"
+#include "mongo/executor/task_executor.h"
+#include "mongo/s/query/cluster_client_cursor_params.h"
+#include "mongo/s/query/async_cluster_client_cursor.h"
+#include "mongo/util/net/hostandport.h"
+
+namespace mongo {
+
+/**
+ * ClusterClientCursor is used to generate results from cursor-generating commands on one or
+ * more remote hosts. A cursor-generating command (e.g. the find command) is one that
+ * establishes a ClientCursor and a matching cursor id on the remote host. In order to retrieve
+ * all command results, getMores must be issued against each of the remote cursors until they
+ * are exhausted.
+ *
+ * ClusterClientCursor provides a simple blocking interface wrapping AsyncClientCursor's
+ * non-blocking interface.
+ *
+ * Does not throw exceptions.
+ */
+class ClusterClientCursor {
+public:
+    /**
+     * Constructs a cluster client cursor.
+     */
+    ClusterClientCursor(executor::TaskExecutor* executor,
+                        const ClusterClientCursorParams& params,
+                        const std::vector<HostAndPort>& remotes);
+
+    /**
+     * Returns the next available result document (along with an ok status). May block waiting
+     * for results from remote nodes.
+     *
+     * If there are no further results, the end of the stream is indicated with boost::none and
+     * an ok status.
+     *
+     * A non-ok status is returned in case of any error.
+     */
+    StatusWith<boost::optional<BSONObj>> next();
+
+    /**
+     * Must be called before destruction to abandon a not-yet-exhausted cursor. If next() has
+     * already returned boost::none, then the cursor is exhausted and is safe to destroy.
+     *
+     * May block waiting for responses from remote hosts.
+     */
+    void kill();
+
+private:
+    // Not owned here.
+    executor::TaskExecutor* _executor;
+
+    const ClusterClientCursorParams _params;
+
+    // Does work of scheduling remote work and merging results.
+    AsyncClusterClientCursor _accc;
+};
+
+}  // namespace mongo