SERVER-31184 Make servers automatically set up config.system.sessions

1 files changed, 117 insertions, 0 deletions

diff --git a/src/mongo/db/sessions_collection_config_server.cpp b/src/mongo/db/sessions_collection_config_server.cpp
new file mode 100644
index 00000000000..9051a73f849
--- /dev/null
+++ b/src/mongo/db/sessions_collection_config_server.cpp
@@ -0,0 +1,117 @@
+/**
+ *    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.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kControl
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/sessions_collection_config_server.h"
+
+#include "mongo/client/query.h"
+#include "mongo/db/dbdirectclient.h"
+#include "mongo/db/logical_session_id.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/rpc/get_status_from_command_result.h"
+#include "mongo/s/client/shard_registry.h"
+#include "mongo/s/commands/cluster_commands_helpers.h"
+#include "mongo/s/grid.h"
+#include "mongo/s/request_types/shard_collection_gen.h"
+#include "mongo/util/log.h"
+
+namespace mongo {
+
+// Returns an error if the collection didn't exist and we couldn't
+// shard it into existence, either.
+Status SessionsCollectionConfigServer::_shardCollectionIfNeeded(OperationContext* opCtx) {
+    // First, check if the collection is already sharded.
+    auto res = _checkCacheForSessionsCollection(opCtx);
+    if (res.isOK()) {
+        return res;
+    }
+
+    // If we don't have any shards, we can't set up this collection yet.
+    if (Grid::get(opCtx)->shardRegistry()->getNumShards() == 0) {
+        return {ErrorCodes::ShardNotFound,
+                "Cannot create config.system.sessions until there are shards"};
+    }
+
+    // First, shard the sessions collection to create it.
+    ConfigsvrShardCollectionRequest shardCollection;
+    shardCollection.set_configsvrShardCollection(
+        NamespaceString(SessionsCollection::kSessionsFullNS.toString()));
+    shardCollection.setKey(BSON("_id" << 1));
+
+    DBDirectClient client(opCtx);
+    BSONObj info;
+    if (!client.runCommand("admin", shardCollection.toBSON(), info)) {
+        return getStatusFromCommandResult(info);
+    }
+
+    return Status::OK();
+}
+
+Status SessionsCollectionConfigServer::_generateIndexesIfNeeded(OperationContext* opCtx) {
+    auto res =
+        scatterGatherOnlyVersionIfUnsharded(opCtx,
+                                            SessionsCollection::kSessionsDb.toString(),
+                                            NamespaceString(SessionsCollection::kSessionsFullNS),
+                                            SessionsCollection::generateCreateIndexesCmd(),
+                                            ReadPreferenceSetting::get(opCtx),
+                                            Shard::RetryPolicy::kNoRetry);
+    return res.getStatus();
+}
+
+Status SessionsCollectionConfigServer::setupSessionsCollection(OperationContext* opCtx) {
+    stdx::lock_guard<stdx::mutex> lk(_mutex);
+    {
+        // Only try to set up this collection until we have done so successfully once.
+        // Note: if there is a config server election, it's possible that two different
+        // primaries could both run the createIndexes scatter-gather query; this is ok.
+        if (_collectionSetUp) {
+            return Status::OK();
+        }
+
+        auto res = _shardCollectionIfNeeded(opCtx);
+        if (!res.isOK()) {
+            log() << "Failed to create config.system.sessions: " << res.reason()
+                  << ", will try again at the next refresh interval";
+            return res;
+        }
+
+        res = _generateIndexesIfNeeded(opCtx);
+        if (!res.isOK()) {
+            log() << "Failed to generate TTL index for config.system.sessions on all shards, "
+                  << "will try again on the next refresh interval";
+        }
+
+        _collectionSetUp = true;
+        return res;
+    }
+}
+
+}  // namespace mongo