SERVER-33639 Protect against distlock acquisition timeout at createDatabase time

5 files changed, 172 insertions, 0 deletions

diff --git a/src/mongo/db/s/config/configsvr_create_database_command.cpp b/src/mongo/db/s/config/configsvr_create_database_command.cpp
index 86690de4e2e..b5f84c94911 100644
--- a/src/mongo/db/s/config/configsvr_create_database_command.cpp
+++ b/src/mongo/db/s/config/configsvr_create_database_command.cpp
@@ -122,6 +122,9 @@ public:
 
         // Remove the backwards compatible lock after 3.6 ships.
         auto const catalogClient = Grid::get(opCtx)->catalogClient();
+        auto scopedLock =
+            ShardingCatalogManager::get(opCtx)->serializeCreateDatabase(opCtx, dbname);
+
         auto backwardsCompatibleDbDistLock = uassertStatusOK(
             catalogClient->getDistLockManager()->lock(opCtx,
                                                       dbname + "-movePrimary",
diff --git a/src/mongo/s/catalog/SConscript b/src/mongo/s/catalog/SConscript
index 23329d25999..e39a8cf831c 100644
--- a/src/mongo/s/catalog/SConscript
+++ b/src/mongo/s/catalog/SConscript
@@ -145,6 +145,7 @@ env.Library(
         'sharding_catalog_manager_database_operations.cpp',
         'sharding_catalog_manager_shard_operations.cpp',
         'sharding_catalog_manager_zone_operations.cpp',
+        'namespace_serializer.cpp',
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/db/catalog/catalog_raii',
diff --git a/src/mongo/s/catalog/namespace_serializer.cpp b/src/mongo/s/catalog/namespace_serializer.cpp
new file mode 100644
index 00000000000..883f37d2e1c
--- /dev/null
+++ b/src/mongo/s/catalog/namespace_serializer.cpp
@@ -0,0 +1,80 @@
+/**
+ *    Copyright (C) 2018 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::kDefault
+#include "mongo/platform/basic.h"
+
+#include "mongo/s/catalog/namespace_serializer.h"
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include "mongo/db/namespace_string.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/s/catalog/sharding_catalog_manager.h"
+#include "mongo/util/log.h"
+#include "mongo/util/scopeguard.h"
+
+namespace mongo {
+
+NamespaceSerializer::NamespaceSerializer() {}
+
+NamespaceSerializer::ScopedLock::ScopedLock(StringData ns, NamespaceSerializer& nsSerializer)
+    : _ns(ns.toString()), _nsSerializer(nsSerializer) {}
+
+NamespaceSerializer::ScopedLock::~ScopedLock() {
+    stdx::unique_lock<stdx::mutex> lock(_nsSerializer._mutex);
+    auto iter = _nsSerializer._inProgressMap.find(_ns);
+
+    iter->second->numWaiting--;
+    iter->second->isInProgress = false;
+    iter->second->cvLocked.notify_one();
+
+    if (iter->second->numWaiting == 0) {
+        _nsSerializer._inProgressMap.erase(_ns);
+    }
+}
+
+NamespaceSerializer::ScopedLock NamespaceSerializer::lock(OperationContext* opCtx, StringData nss) {
+    stdx::unique_lock<stdx::mutex> lock(_mutex);
+    auto iter = _inProgressMap.find(nss);
+
+    if (iter == _inProgressMap.end()) {
+        _inProgressMap.try_emplace(nss, std::make_shared<NSLock>());
+    } else {
+        auto& nsLock = iter->second;
+        nsLock->numWaiting++;
+        opCtx->waitForConditionOrInterrupt(
+            nsLock->cvLocked, lock, [&nsLock]() { return !nsLock->isInProgress; });
+        nsLock->isInProgress = true;
+    }
+
+    return ScopedLock(nss, *this);
+}
+
+}  // namespace mongo
diff --git a/src/mongo/s/catalog/namespace_serializer.h b/src/mongo/s/catalog/namespace_serializer.h
new file mode 100644
index 00000000000..8683b7578b1
--- /dev/null
+++ b/src/mongo/s/catalog/namespace_serializer.h
@@ -0,0 +1,77 @@
+/**
+ *    Copyright (C) 2018 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 <map>
+#include <memory>
+#include <string>
+
+#include "mongo/base/status.h"
+#include "mongo/base/status_with.h"
+#include "mongo/db/namespace_string.h"
+#include "mongo/stdx/condition_variable.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/util/string_map.h"
+
+namespace mongo {
+
+class OperationContext;
+
+class NamespaceSerializer {
+    MONGO_DISALLOW_COPYING(NamespaceSerializer);
+
+public:
+    class ScopedLock {
+    public:
+        ~ScopedLock();
+
+    private:
+        friend class NamespaceSerializer;
+        ScopedLock(StringData ns, NamespaceSerializer& nsSerializer);
+
+        std::string _ns;
+        NamespaceSerializer& _nsSerializer;
+    };
+
+    NamespaceSerializer();
+
+    ScopedLock lock(OperationContext* opCtx, StringData ns);
+
+private:
+    struct NSLock {
+        stdx::condition_variable cvLocked;
+        int numWaiting = 1;
+        bool isInProgress = true;
+    };
+
+    stdx::mutex _mutex;
+    StringMap<std::shared_ptr<NSLock>> _inProgressMap;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/s/catalog/sharding_catalog_manager.h b/src/mongo/s/catalog/sharding_catalog_manager.h
index 670c57fb678..56457993a78 100644
--- a/src/mongo/s/catalog/sharding_catalog_manager.h
+++ b/src/mongo/s/catalog/sharding_catalog_manager.h
@@ -33,6 +33,7 @@
 #include "mongo/db/concurrency/d_concurrency.h"
 #include "mongo/db/repl/optime_with.h"
 #include "mongo/executor/task_executor.h"
+#include "mongo/s/catalog/namespace_serializer.h"
 #include "mongo/s/catalog/type_chunk.h"
 #include "mongo/s/catalog/type_database.h"
 #include "mongo/s/catalog/type_shard.h"
@@ -203,6 +204,14 @@ public:
     DatabaseType createDatabase(OperationContext* opCtx, const std::string& dbName);
 
     /**
+     * Creates a ScopedLock on the database name in _namespaceSerializer. This is to prevent
+     * timeouts waiting on the dist lock if multiple threads attempt to create the same db.
+     */
+    auto serializeCreateDatabase(OperationContext* opCtx, StringData dbName) {
+        return _namespaceSerializer.lock(opCtx, dbName);
+    }
+
+    /**
      * Creates the database if it does not exist, then marks its entry in config.databases as
      * sharding-enabled.
      *
@@ -478,6 +487,8 @@ private:
      * be removed while they are running (such as removeShardFromZone) to take this in shared mode.
      */
     Lock::ResourceMutex _kShardMembershipLock;
+
+    NamespaceSerializer _namespaceSerializer;
 };
 
 }  // namespace mongo