SERVER-49563 Create ReshardingCoordinator class

3 files changed, 230 insertions, 0 deletions

diff --git a/src/mongo/db/s/SConscript b/src/mongo/db/s/SConscript
index 12904d41747..eaad8ca1d68 100644
--- a/src/mongo/db/s/SConscript
+++ b/src/mongo/db/s/SConscript
@@ -68,6 +68,7 @@ env.Library(
         'range_deletion_util.cpp',
         'read_only_catalog_cache_loader.cpp',
         'resharding_util.cpp',
+        'resharding/resharding_coordinator.cpp',
         'scoped_operation_completion_sharding_actions.cpp',
         'session_catalog_migration_destination.cpp',
         'session_catalog_migration_source.cpp',
diff --git a/src/mongo/db/s/resharding/resharding_coordinator.cpp b/src/mongo/db/s/resharding/resharding_coordinator.cpp
new file mode 100644
index 00000000000..61b586a5294
--- /dev/null
+++ b/src/mongo/db/s/resharding/resharding_coordinator.cpp
@@ -0,0 +1,92 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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.
+ */
+
+#include "mongo/db/s/resharding/resharding_coordinator.h"
+
+#include "mongo/db/service_context.h"
+#include "mongo/s/catalog/type_chunk.h"
+#include "mongo/s/shard_id.h"
+
+namespace mongo {
+
+namespace {
+const auto getReshardingCoordinator = ServiceContext::declareDecoration<ReshardingCoordinator>();
+}  // namespace
+
+ReshardingCoordinator::ReshardingCoordinator() = default;
+
+ReshardingCoordinator::~ReshardingCoordinator() {
+    // TODO SERVER-49569 uncomment line below
+    // invariant(_reshardingOperationsInProgress.empty());
+}
+
+ReshardingCoordinator& ReshardingCoordinator::get(ServiceContext* serviceContext) {
+    return getReshardingCoordinator(serviceContext);
+}
+
+ReshardingCoordinator& ReshardingCoordinator::get(OperationContext* opCtx) {
+    return get(opCtx->getServiceContext());
+}
+
+// TODO SERVER-49570
+void ReshardingCoordinator::onNewReshardCollection(const NamespaceString& nss,
+                                                   const std::vector<ShardId>& donors,
+                                                   const std::vector<ShardId>& recipients,
+                                                   const std::vector<ChunkType>& initialChunks) {}
+
+// TODO	SERVER-49572
+void ReshardingCoordinator::onRecipientReportsCreatedCollection(const NamespaceString& nss,
+                                                                const ShardId& recipient) {}
+
+// TODO SERVER-49573
+void ReshardingCoordinator::onDonorReportsMinFetchTimestamp(const NamespaceString& nss,
+                                                            const ShardId& donor,
+                                                            Timestamp timestamp) {}
+
+// TODO SERVER-49574
+void ReshardingCoordinator::onRecipientFinishesCloning(const NamespaceString& nss,
+                                                       const ShardId& recipient) {}
+
+// TODO SERVER-49575
+void ReshardingCoordinator::onRecipientReportsStrictlyConsistent(const NamespaceString& nss,
+                                                                 const ShardId& recipient) {}
+
+// TODO SERVER-49576
+void ReshardingCoordinator::onRecipientRenamesCollection(const NamespaceString& nss,
+                                                         const ShardId& recipient) {}
+
+// TODO SERVER-49577
+void ReshardingCoordinator::onDonorDropsOriginalCollection(const NamespaceString& nss,
+                                                           const ShardId& donor) {}
+
+// TODO SERVER-49578
+void ReshardingCoordinator::onRecipientReportsUnrecoverableError(const NamespaceString& nss,
+                                                                 const ShardId& recipient,
+                                                                 Status error) {}
+}  // namespace mongo
diff --git a/src/mongo/db/s/resharding/resharding_coordinator.h b/src/mongo/db/s/resharding/resharding_coordinator.h
new file mode 100644
index 00000000000..9de335abf40
--- /dev/null
+++ b/src/mongo/db/s/resharding/resharding_coordinator.h
@@ -0,0 +1,137 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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 <vector>
+
+#include "mongo/base/status.h"
+#include "mongo/bson/timestamp.h"
+#include "mongo/platform/mutex.h"
+
+namespace mongo {
+
+class ChunkType;
+class NamespaceString;
+class OperationContext;
+class ServiceContext;
+class ShardId;
+
+/**
+ * Manages active resharding operations and holds a catalog of ReshardingCoordinatorStateMachine
+ * objects indexed by collection namespace.
+ *
+ * There is one instance of this object per service context.
+ */
+
+class ReshardingCoordinator {
+    ReshardingCoordinator(const ReshardingCoordinator&) = delete;
+    ReshardingCoordinator& operator=(const ReshardingCoordinator&) = delete;
+
+public:
+    ReshardingCoordinator();
+    ~ReshardingCoordinator();
+
+    static ReshardingCoordinator& get(ServiceContext* serviceContext);
+    static ReshardingCoordinator& get(OperationContext* opCtx);
+
+    /**
+     * Creates a new ReshardingCoordinatorStateMachine for the resharding operation on the
+     * collection 'nss' and adds it to _reshardingOperationsInProgress. Updates on-disk metadata to
+     * indicate that the collection is being resharded.
+     */
+    void onNewReshardCollection(const NamespaceString& nss,
+                                const std::vector<ShardId>& donors,
+                                const std::vector<ShardId>& recipients,
+                                const std::vector<ChunkType>& initialChunks);
+
+    /**
+     * Called when each recipient reports it has finished creating the collection. Triggers a state
+     * transition and updates on-disk metadata if this recipient is the last to report it has
+     * finished creating the collection.
+     */
+    void onRecipientReportsCreatedCollection(const NamespaceString& nss, const ShardId& recipient);
+
+    /**
+     * Called when each donor reports its minFetchTimestamp. If this donor is the last to report its
+     * minFetchTimestamp, selects the highest timestamp among all donors to be the fetchTimestamp,
+     * triggers a state change, and updates on-disk metadata.
+     */
+    void onDonorReportsMinFetchTimestamp(const NamespaceString& nss,
+                                         const ShardId& donor,
+                                         Timestamp timestamp);
+
+    /**
+     * Called when each recipient finishes cloning and enters steady-state. Triggers a state
+     * transition and updates on-disk metadata if this recipient is the last to report it has
+     * finished cloning the collection.
+     */
+    void onRecipientFinishesCloning(const NamespaceString& nss, const ShardId& recipient);
+
+    /**
+     * Called when a recipient has met the following criteria:
+     * 1. Has been notified by all donors all writes must be run in transactions and
+     * 2. Has applied all oplog entries and
+     * 3. Has entered strict-consistency state
+     *
+     * If the recipient is the last to report it is in strict-consistency, commits the resharding
+     * operation, triggers a state transition, and updates on-disk metadata.
+     */
+    void onRecipientReportsStrictlyConsistent(const NamespaceString& nss, const ShardId& recipient);
+
+    /**
+     * Called when each recipient finishes renaming the temporary collection. Triggers a state
+     * transition and updates on-disk metadata if this recipient is the last to report it has
+     * finished renaming.
+     */
+    void onRecipientRenamesCollection(const NamespaceString& nss, const ShardId& recipient);
+
+    /**
+     * Called when each donor finishes dropping the original collection. Triggers a state transition
+     * and updates on-disk metadata if this donor is the last to report it has finished dropping.
+     */
+    void onDonorDropsOriginalCollection(const NamespaceString& nss, const ShardId& donor);
+
+    /**
+     * Called if a recipient reports an unrecoverable error.
+     */
+    void onRecipientReportsUnrecoverableError(const NamespaceString& nss,
+                                              const ShardId& recipient,
+                                              Status error);
+
+private:
+    // Protects the state below
+    Mutex _mutex = MONGO_MAKE_LATCH("ReshardingCoordinator::_mutex");
+
+    // Contains ReshardingCoordinatorStateMachine objects by collection namespace.
+    // TODO SERVER-49569 uncomment line below
+    // StringMap<ReshardingCoordinatorStateMachine> _reshardingOperationsInProgress;
+};
+
+}  // namespace mongo