SERVER-29694 Read-only shards should not try to persist the collection routing information locally

4 files changed, 146 insertions, 3 deletions

diff --git a/src/mongo/db/s/SConscript b/src/mongo/db/s/SConscript
index d3c7c682c0b..1a9c825aee3 100644
--- a/src/mongo/db/s/SConscript
+++ b/src/mongo/db/s/SConscript
@@ -74,6 +74,7 @@ env.Library(
         'move_timing_helper.cpp',
         'namespace_metadata_change_notifications.cpp',
         'operation_sharding_state.cpp',
+        'read_only_catalog_cache_loader.cpp',
         'shard_identity_rollback_notifier.cpp',
         'shard_metadata_util.cpp',
         'shard_server_catalog_cache_loader.cpp',
diff --git a/src/mongo/db/s/read_only_catalog_cache_loader.cpp b/src/mongo/db/s/read_only_catalog_cache_loader.cpp
new file mode 100644
index 00000000000..007a6203489
--- /dev/null
+++ b/src/mongo/db/s/read_only_catalog_cache_loader.cpp
@@ -0,0 +1,70 @@
+/**
+ *    Copyright (C) 2017 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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/s/read_only_catalog_cache_loader.h"
+
+#include "mongo/db/operation_context.h"
+
+namespace mongo {
+
+using CollectionAndChangedChunks = CatalogCacheLoader::CollectionAndChangedChunks;
+
+void ReadOnlyCatalogCacheLoader::initializeReplicaSetRole(bool isPrimary) {
+    return;
+}
+
+void ReadOnlyCatalogCacheLoader::onStepDown() {
+    return;
+}
+
+void ReadOnlyCatalogCacheLoader::onStepUp() {
+    return;
+}
+
+void ReadOnlyCatalogCacheLoader::notifyOfCollectionVersionUpdate(OperationContext* opCtx,
+                                                                 const NamespaceString& nss,
+                                                                 const ChunkVersion& version) {
+    return;
+}
+
+Status ReadOnlyCatalogCacheLoader::waitForCollectionVersion(OperationContext* opCtx,
+                                                            const NamespaceString& nss,
+                                                            const ChunkVersion& version) {
+    return Status::OK();
+}
+
+std::shared_ptr<Notification<void>> ReadOnlyCatalogCacheLoader::getChunksSince(
+    const NamespaceString& nss,
+    ChunkVersion version,
+    stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn) {
+    return _configServerLoader.getChunksSince(nss, version, callbackFn);
+}
+
+}  // namespace mongo
diff --git a/src/mongo/db/s/read_only_catalog_cache_loader.h b/src/mongo/db/s/read_only_catalog_cache_loader.h
new file mode 100644
index 00000000000..1615ba55c16
--- /dev/null
+++ b/src/mongo/db/s/read_only_catalog_cache_loader.h
@@ -0,0 +1,66 @@
+/**
+ *    Copyright (C) 2017 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 "mongo/s/catalog_cache_loader.h"
+#include "mongo/s/config_server_catalog_cache_loader.h"
+
+namespace mongo {
+
+/**
+ * Contains a ConfigServerCatalogCacheLoader for remote metadata loading. Inactive functions simply
+ * return, rather than invariant, so this class can be plugged into the shard server for read-only
+ * mode, where persistence should not be attempted.
+ */
+class ReadOnlyCatalogCacheLoader final : public CatalogCacheLoader {
+public:
+    /**
+     * These functions do nothing and simply return.
+     */
+    void initializeReplicaSetRole(bool isPrimary) override;
+    void onStepDown() override;
+    void onStepUp() override;
+    void notifyOfCollectionVersionUpdate(OperationContext* opCtx,
+                                         const NamespaceString& nss,
+                                         const ChunkVersion& version) override;
+    Status waitForCollectionVersion(OperationContext* opCtx,
+                                    const NamespaceString& nss,
+                                    const ChunkVersion& version) override;
+
+    std::shared_ptr<Notification<void>> getChunksSince(
+        const NamespaceString& nss,
+        ChunkVersion version,
+        stdx::function<void(OperationContext*, StatusWith<CollectionAndChangedChunks>)> callbackFn)
+        override;
+
+private:
+    ConfigServerCatalogCacheLoader _configServerLoader;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/db/s/sharding_initialization_mongod.cpp b/src/mongo/db/s/sharding_initialization_mongod.cpp
index d109854769b..50bff361b30 100644
--- a/src/mongo/db/s/sharding_initialization_mongod.cpp
+++ b/src/mongo/db/s/sharding_initialization_mongod.cpp
@@ -38,6 +38,7 @@
 #include "mongo/client/remote_command_targeter_factory_impl.h"
 #include "mongo/db/logical_time_metadata_hook.h"
 #include "mongo/db/operation_context.h"
+#include "mongo/db/s/read_only_catalog_cache_loader.h"
 #include "mongo/db/s/shard_server_catalog_cache_loader.h"
 #include "mongo/db/s/sharding_egress_metadata_hook_for_mongod.h"
 #include "mongo/db/server_options.h"
@@ -88,9 +89,14 @@ Status initializeGlobalShardingStateForMongod(OperationContext* opCtx,
         stdx::make_unique<ShardFactory>(std::move(buildersMap), std::move(targeterFactory));
 
     if (serverGlobalParams.clusterRole == ClusterRole::ShardServer) {
-        CatalogCacheLoader::set(opCtx->getServiceContext(),
-                                stdx::make_unique<ShardServerCatalogCacheLoader>(
-                                    stdx::make_unique<ConfigServerCatalogCacheLoader>()));
+        if (storageGlobalParams.readOnly) {
+            CatalogCacheLoader::set(opCtx->getServiceContext(),
+                                    stdx::make_unique<ReadOnlyCatalogCacheLoader>());
+        } else {
+            CatalogCacheLoader::set(opCtx->getServiceContext(),
+                                    stdx::make_unique<ShardServerCatalogCacheLoader>(
+                                        stdx::make_unique<ConfigServerCatalogCacheLoader>()));
+        }
     } else {
         CatalogCacheLoader::set(opCtx->getServiceContext(),
                                 stdx::make_unique<ConfigServerCatalogCacheLoader>());