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/**
* 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/base/status_with.h"
#include "mongo/db/logical_session_id.h"
#include "mongo/db/service_liason.h"
#include "mongo/db/sessions_collection.h"
#include "mongo/db/time_proof_service.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/lru_cache.h"
namespace mongo {
class Client;
class OperationContext;
class ServiceContext;
extern int logicalSessionRecordCacheSize;
extern int logicalSessionRefreshMinutes;
/**
* A thread-safe cache structure for logical session records.
*
* The cache takes ownership of the passed-in ServiceLiason and
* SessionsCollection helper types.
*/
class LogicalSessionCache {
public:
/**
* Decorate the ServiceContext with a LogicalSessionCache instance.
*/
static LogicalSessionCache* get(ServiceContext* service);
static LogicalSessionCache* get(OperationContext* opCtx);
static void set(ServiceContext* service, std::unique_ptr<LogicalSessionCache> sessionCache);
static constexpr int kLogicalSessionCacheDefaultCapacity = 10000;
static constexpr Minutes kLogicalSessionDefaultRefresh = Minutes(5);
/**
* An Options type to support the LogicalSessionCache.
*/
struct Options {
Options(){};
/**
* The number of session records to keep in the cache.
*
* May be set with --setParameter logicalSessionRecordCacheSize=X.
*/
int capacity = logicalSessionRecordCacheSize;
/**
* A timeout value to use for sessions in the cache, in minutes.
*
* By default, this is set to 30 minutes.
*
* May be set with --setParameter localLogicalSessionTimeoutMinutes=X.
*/
Minutes sessionTimeout = Minutes(localLogicalSessionTimeoutMinutes);
/**
* The interval over which the cache will refresh session records.
*
* By default, this is set to every 5 minutes. If the caller is
* setting the sessionTimeout by hand, it is suggested that they
* consider also setting the refresh interval accordingly.
*
* May be set with --setParameter logicalSessionRefreshMinutes=X.
*/
Minutes refreshInterval = Minutes(logicalSessionRefreshMinutes);
};
/**
* Construct a new session cache.
*/
explicit LogicalSessionCache(std::unique_ptr<ServiceLiason> service,
std::unique_ptr<SessionsCollection> collection,
Options options = Options{});
LogicalSessionCache(const LogicalSessionCache&) = delete;
LogicalSessionCache operator=(const LogicalSessionCache&) = delete;
~LogicalSessionCache();
/**
* If the cache contains a record for this LogicalSessionId, promotes that lsid
* to be the most recently used and updates its lastUse date to be the current
* time. Otherwise, returns an error.
*
* This method does not issue networking calls.
*/
Status promote(LogicalSessionId lsid);
/**
* If the cache contains a record for this LogicalSessionId, promotes it.
* Otherwise, attempts to fetch the record for this LogicalSessionId from the
* sessions collection, and returns the record if found. Otherwise, returns an error.
*
* This method may issue networking calls.
*/
Status fetchAndPromote(OperationContext* opCtx, const LogicalSessionId& lsid);
/**
* Inserts a new authoritative session record into the cache. This method will
* insert the authoritative record into the sessions collection. This method
* should only be used when starting new sessions and should not be used to
* insert records for existing sessions.
*/
Status startSession(OperationContext* opCtx, LogicalSessionRecord record);
/**
* Removes all local records in this cache. Does not remove the corresponding
* authoritative session records from the sessions collection.
*/
void clear();
/**
* Refreshes the cache synchronously. This flushes all pending refreshes and
* inserts to the sessions collection.
*/
void refreshNow(Client* client);
/**
* Returns the current time.
*/
Date_t now();
private:
/**
* Internal methods to handle scheduling and perform refreshes for active
* session records contained within the cache.
*/
void _refresh(Client* client);
/**
* Returns true if a record has passed its given expiration.
*/
bool _isDead(const LogicalSessionRecord& record, Date_t now) const;
/**
* Takes the lock and inserts the given record into the cache.
*/
boost::optional<LogicalSessionRecord> _addToCache(LogicalSessionRecord record);
const Minutes _refreshInterval;
const Minutes _sessionTimeout;
std::unique_ptr<ServiceLiason> _service;
std::unique_ptr<SessionsCollection> _sessionsColl;
stdx::mutex _cacheMutex;
LRUCache<LogicalSessionId, LogicalSessionRecord, LogicalSessionIdHash> _cache;
};
} // namespace mongo
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