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/**
* Copyright (C) 2019-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 <map>
#include "mongo/db/operation_context.h"
#include "mongo/db/read_write_concern_defaults_gen.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/db/service_context.h"
#include "mongo/db/write_concern_options.h"
#include "mongo/platform/mutex.h"
#include "mongo/util/concurrency/thread_pool.h"
#include "mongo/util/concurrency/with_lock.h"
#include "mongo/util/read_through_cache.h"
namespace mongo {
/**
* Class to manage Read Concern and Write Concern (RWC) defaults.
*/
class ReadWriteConcernDefaults {
public:
/**
* Consistent names for the classes that define a ReadConcern and a WriteConcern.
*/
using ReadConcern = repl::ReadConcernArgs;
using WriteConcern = WriteConcernOptions;
using FetchDefaultsFn = unique_function<boost::optional<RWConcernDefault>(OperationContext*)>;
static constexpr StringData readConcernFieldName = ReadConcern::kReadConcernFieldName;
static constexpr StringData writeConcernFieldName = WriteConcern::kWriteConcernField;
// The _id of the persisted default read/write concern document.
static constexpr StringData kPersistedDocumentId = "ReadWriteConcernDefaults"_sd;
static ReadWriteConcernDefaults& get(ServiceContext* service);
static ReadWriteConcernDefaults& get(OperationContext* opCtx);
static void create(ServiceContext* service, FetchDefaultsFn fetchDefaultsFn);
ReadWriteConcernDefaults(ServiceContext* service, FetchDefaultsFn fetchDefaultsFn);
~ReadWriteConcernDefaults();
/**
* Syntactic sugar around 'getDefault' below. A return value of boost::none means that there is
* no default specified for that particular concern.
*/
boost::optional<ReadConcern> getDefaultReadConcern(OperationContext* opCtx);
boost::optional<WriteConcern> getDefaultWriteConcern(OperationContext* opCtx);
class RWConcernDefaultAndTime : public RWConcernDefault {
public:
RWConcernDefaultAndTime() = default;
RWConcernDefaultAndTime(RWConcernDefault rwcd, Date_t localUpdateWallClockTime)
: RWConcernDefault(std::move(rwcd)),
_localUpdateWallClockTime(localUpdateWallClockTime) {}
Date_t localUpdateWallClockTime() const {
return _localUpdateWallClockTime;
}
private:
Date_t _localUpdateWallClockTime;
};
/**
* Returns the current set of read/write concern defaults along with the wallclock time when
* they were cached (for diagnostic purposes).
*/
RWConcernDefaultAndTime getDefault(OperationContext* opCtx) {
return _getDefault(opCtx).value_or(RWConcernDefaultAndTime());
}
/**
* Returns true if the RC level is permissible to use as a default, and false if it cannot be a
* RC default.
*/
static bool isSuitableReadConcernLevel(repl::ReadConcernLevel level);
/**
* Checks if the given RWC is suitable to use as a default, and uasserts if not.
*/
static void checkSuitabilityAsDefault(const ReadConcern& rc);
static void checkSuitabilityAsDefault(const WriteConcern& wc);
/**
* Examines a document key affected by a write to config.settings and will register a WUOW
* onCommit handler that invalidates this cache when the operation commits if the write affects
* the read/write concern defaults document.
*/
void observeDirectWriteToConfigSettings(OperationContext* opCtx,
BSONElement idElem,
boost::optional<BSONObj> newDoc);
/**
* Generates a new read and write concern default to be persisted on disk, without updating the
* cached value.
* At least one of the `rc` or `wc` params must be set.
* Will generate and use a new epoch and setTime for the updated defaults, which are returned.
* Validates the supplied read and write concerns can serve as defaults.
*/
RWConcernDefault generateNewConcerns(OperationContext* opCtx,
const boost::optional<ReadConcern>& rc,
const boost::optional<WriteConcern>& wc);
/**
* Invalidates the cached RWC defaults, causing them to be refreshed.
*
* After this call returns, the read methods below (getDefault, getDefaultReadConcern,
* getDefaultWriteConcern) may continue returning the invalidated defaults, until they have been
* replaced by the refreshed values. This is to avoid stalling CRUD ops (and other ops that
* need RC/WC) during refresh.
*/
void invalidate();
/**
* Manually looks up the latest defaults, and if their epoch is more recent than the cached
* defaults or indicates there are no defaults, then update the cache with the new defaults.
*/
void refreshIfNecessary(OperationContext* opCtx);
/**
* Sets the given read write concern as the defaults in the cache.
*/
void setDefault(OperationContext* opCtx, RWConcernDefault&& rwc);
private:
enum class Type { kReadWriteConcernEntry };
boost::optional<RWConcernDefaultAndTime> _getDefault(OperationContext* opCtx);
class Cache : public ReadThroughCache<Type, RWConcernDefault> {
Cache(const Cache&) = delete;
Cache& operator=(const Cache&) = delete;
public:
Cache(ServiceContext* service,
ThreadPoolInterface& threadPool,
FetchDefaultsFn fetchDefaultsFn);
virtual ~Cache() = default;
boost::optional<RWConcernDefault> lookup(OperationContext* opCtx);
private:
Mutex _mutex = MONGO_MAKE_LATCH("ReadWriteConcernDefaults::Cache");
FetchDefaultsFn _fetchDefaultsFn;
};
Cache _defaults;
// Thread pool on which to perform loading of the cached RWC defaults
ThreadPool _threadPool;
};
} // namespace mongo
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