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/**
* Copyright (C) 2018-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 <deque>
#include "mongo/db/s/dist_lock_catalog.h"
#include "mongo/db/s/dist_lock_manager.h"
#include "mongo/stdx/thread.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/util/future.h"
namespace mongo {
class ReplSetDistLockManager : public DistLockManager {
public:
// How frequently should the dist lock pinger thread run and write liveness information about
// this instance of the dist lock manager
static const Seconds kDistLockPingInterval;
// How long should the lease on a distributed lock last
static const Minutes kDistLockExpirationTime;
ReplSetDistLockManager(ServiceContext* service,
StringData processID,
std::unique_ptr<DistLockCatalog> catalog,
Milliseconds pingInterval,
Milliseconds lockExpiration);
virtual ~ReplSetDistLockManager();
void startUp() override;
void shutDown(OperationContext* opCtx) override;
std::string getProcessID() override;
Status lockDirect(OperationContext* opCtx,
StringData name,
StringData whyMessage,
Milliseconds waitFor) override;
Status tryLockDirectWithLocalWriteConcern(OperationContext* opCtx,
StringData name,
StringData whyMessage) override;
void unlock(Interruptible* intr, StringData name) override;
void unlockAll(OperationContext* opCtx) override;
/**
* Indicates to the dist lock manager that a step-up has occurred with the specified term. This
* in turn requests that the dist lock manager performs a recovery, freeing all locks it might
* have previously held, before it attempts to acquire any new ones.
*/
void onStepUp(long long term);
void markRecovered_forTest();
private:
/**
* Queue a lock to be unlocked asynchronously with retry until it doesn't error.
*/
SharedSemiFuture<void> _queueUnlock(const OID& lockSessionID, const std::string& name);
/**
* Periodically pings and checks if there are locks queued that needs unlocking.
*/
void doTask();
/**
* Returns true if shutDown was called.
*/
bool isShutDown();
/**
* Returns true if the current process that owns the lock has no fresh pings since
* the lock expiration threshold.
*/
StatusWith<bool> isLockExpired(OperationContext* opCtx,
LocksType lockDoc,
const Milliseconds& lockExpiration);
long long _waitForRecovery(OperationContext* opCtx);
/**
* Data structure for storing information about distributed lock pings.
*/
struct DistLockPingInfo {
DistLockPingInfo();
DistLockPingInfo(StringData processId,
Date_t lastPing,
Date_t configLocalTime,
OID lockSessionId,
OID electionId);
// the process processId of the last known owner of the lock.
std::string processId;
// the ping value from the last owner of the lock.
Date_t lastPing;
// the config server local time when this object was updated.
Date_t configLocalTime;
// last known owner of the lock.
OID lockSessionId;
// the election id of the config server when this object was updated.
// Note: unused by legacy dist lock.
OID electionId;
};
//
// All member variables are labeled with one of the following codes indicating the
// synchronization rules for accessing them.
//
// (F) Self synchronizing.
// (M) Must hold _mutex for access.
// (I) Immutable, no synchronization needed.
// (S) Can only be called inside startUp/shutDown.
//
ServiceContext* const _serviceContext; // (F)
const std::string _processID; // (I)
const std::unique_ptr<DistLockCatalog> _catalog; // (I)
const Milliseconds _pingInterval; // (I)
const Milliseconds _lockExpiration; // (I)
Mutex _mutex = MONGO_MAKE_LATCH("ReplSetDistLockManager::_mutex");
std::unique_ptr<stdx::thread> _execThread; // (S)
// Contains the list of locks queued for unlocking. Among regular unlocks of a properly acquired
// locks, cases when an unlock operation can be queued include:
// 1. First attempt on unlocking resulted in an error.
// 2. Attempting to grab or overtake a lock resulted in an error where we are uncertain
// whether the modification was actually applied or not, and call unlock to make
// sure that it was cleaned up.
struct UnlockRequest {
UnlockRequest(OID lockId, std::string name)
: lockId(std::move(lockId)), name(std::move(name)) {}
OID lockId;
std::string name;
// Will be signaled when the unlock request has completed
SharedPromise<void> unlockCompleted;
};
std::deque<UnlockRequest> _unlockList; // (M)
bool _isShutDown = false; // (M)
stdx::condition_variable _shutDownCV; // (M)
// Map of lockName to last ping information.
stdx::unordered_map<std::string, DistLockPingInfo> _pingHistory; // (M)
// Tracks the state of post step-up recovery.
enum Recovery {
kMustRecover,
kMustWaitForRecovery,
kRecovered,
};
Recovery _recoveryState;
long long _recoveryTerm{-1};
stdx::condition_variable _waitForRecoveryCV;
};
} // namespace mongo
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