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/**
* 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::kSharding
#include "mongo/platform/basic.h"
#include "mongo/db/s/implicit_create_collection.h"
#include <map>
#include <memory>
#include <string>
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/catalog_raii.h"
#include "mongo/db/commands.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/service_context.h"
#include "mongo/s/grid.h"
#include "mongo/s/request_types/create_collection_gen.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
namespace {
/**
* Responsible for explicitly creating collections in the sharding catalog. Also takes care of
* making sure that concurrent attempts to create a collection for the same ns will be
* synchronized and avoid duplicate work as much as possible.
*/
class CreateCollectionSerializer {
public:
explicit CreateCollectionSerializer(NamespaceString ns) : _ns(std::move(ns)) {}
/**
* Initialize this collection so it will be officially tracked in a sharded environment
* by sending the command to the config server to create an entry for this collection in
* the sharding catalog.
*/
Status onCannotImplicitlyCreateCollection(OperationContext* opCtx) noexcept {
invariant(!opCtx->lockState()->isLocked());
{
stdx::unique_lock<stdx::mutex> lg(_mutex);
while (_isInProgress) {
auto status = opCtx->waitForConditionOrInterruptNoAssert(_cvIsInProgress, lg);
if (!status.isOK()) {
return status;
}
}
_isInProgress = true;
}
ON_BLOCK_EXIT([&] {
stdx::lock_guard<stdx::mutex> lg(_mutex);
_isInProgress = false;
_cvIsInProgress.notify_one();
});
try {
// Take the DBLock and CollectionLock directly rather than using AutoGetCollection
// (which calls AutoGetDb) to avoid doing database and shard version checks.
Lock::DBLock dbLock(opCtx, _ns.db(), MODE_IS);
const auto db = dbHolder().get(opCtx, _ns.db());
if (db) {
Lock::CollectionLock collLock(opCtx->lockState(), _ns.ns(), MODE_IS);
if (db->getCollection(opCtx, _ns.ns())) {
// Collection already created, no more work needs to be done.
return Status::OK();
}
}
} catch (const DBException& ex) {
return ex.toStatus();
}
ConfigsvrCreateCollection configCreateCmd;
configCreateCmd.setNs(_ns);
auto statusWith =
Grid::get(opCtx)->shardRegistry()->getConfigShard()->runCommandWithFixedRetryAttempts(
opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
"admin",
CommandHelpers::appendMajorityWriteConcern(configCreateCmd.toBSON()),
Shard::RetryPolicy::kIdempotent);
if (!statusWith.isOK()) {
return statusWith.getStatus();
}
return Shard::CommandResponse::getEffectiveStatus(statusWith.getValue());
}
private:
const NamespaceString _ns;
stdx::mutex _mutex;
stdx::condition_variable _cvIsInProgress;
bool _isInProgress = false;
};
class CreateCollectionSerializerMap {
public:
std::shared_ptr<CreateCollectionSerializer> getForNs(const NamespaceString& ns) {
stdx::lock_guard<stdx::mutex> lg(_mutex);
auto iter = _inProgressMap.find(ns.ns());
if (iter == _inProgressMap.end()) {
std::tie(iter, std::ignore) =
_inProgressMap.emplace(ns.ns(), std::make_shared<CreateCollectionSerializer>(ns));
}
return iter->second;
}
void cleanupNs(const NamespaceString& ns) {
stdx::lock_guard<stdx::mutex> lg(_mutex);
_inProgressMap.erase(ns.ns());
}
private:
stdx::mutex _mutex;
std::map<std::string, std::shared_ptr<CreateCollectionSerializer>> _inProgressMap;
};
const auto createCollectionSerializerMap =
ServiceContext::declareDecoration<CreateCollectionSerializerMap>();
} // unnamed namespace
Status onCannotImplicitlyCreateCollection(OperationContext* opCtx,
const NamespaceString& ns) noexcept {
auto& handlerMap = createCollectionSerializerMap(opCtx->getServiceContext());
auto status = handlerMap.getForNs(ns)->onCannotImplicitlyCreateCollection(opCtx);
if (status.isOK()) {
handlerMap.cleanupNs(ns);
} else {
// We only cleanup on success because that is our last chance for us to do so. This avoids
// the scenario with multiple handlers for the same ns to exist at the same time if we
// cleanup regardless of success or failure. On the other hand, cleaning it up only on
// success can cause the handler to never get cleaned up when the collection was
// successfully created, but this shard got an error response from the config
// server.
}
return status;
}
} // namespace mongo
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