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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.
*/
#include <limits>
#include <list>
#include "mongo/db/client.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/operation_id.h"
#include "mongo/db/service_context.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/concurrency/with_lock.h"
#include "mongo/util/testing_proctor.h"
namespace mongo {
namespace {
const auto getOperationIdManager = ServiceContext::declareDecoration<OperationIdManager>();
} // namespace
OperationIdManager& OperationIdManager::get(ServiceContext* svcCtx) noexcept {
return (*svcCtx)[getOperationIdManager];
}
struct Lease {
OperationId start;
};
struct OperationIdManager::IdPool {
Lease lease(WithLock) {
if (exhaustedUniqueIds) {
invariant(!released.empty(),
"Process has run out of OperationIds. This indicates that there are too many "
"open client connections for the process to handle.");
auto l = released.front();
released.pop_front();
return l;
}
auto leaseStart = nextId;
nextId += leaseSize;
if (MONGO_unlikely(std::numeric_limits<OperationId>::max() - nextId < leaseSize)) {
exhaustedUniqueIds = true;
}
return {leaseStart};
}
void releaseLease(WithLock, Lease lease) {
released.push_back(lease);
}
void setLeaseSize_forTest(size_t size) {
invariant(!exhaustedUniqueIds && !nextId,
"Cannot change lease size after a lease is issued");
leaseSize = size;
}
bool exhaustedUniqueIds{false};
OperationId nextId{0};
std::list<Lease> released;
size_t leaseSize = OperationIdManager::kDefaultLeaseSize;
};
OperationIdManager::OperationIdManager() : _pool(std::make_unique<OperationIdManager::IdPool>()) {}
#define VERIFY_LEASE_START(start, bitmask) invariant((start & ~bitmask) == 0)
struct ClientState {
size_t unused = 0;
Lease lease;
OperationId nextId;
bool isInitialized = false;
};
namespace {
const auto getClientState = Client::declareDecoration<ClientState>();
} // namespace
OperationId OperationIdManager::issueForClient(Client* client) noexcept {
auto getLease = [this, client](Lease* oldLease) {
stdx::lock_guard lk(_mutex);
auto lease = _pool->lease(lk);
VERIFY_LEASE_START(lease.start, _leaseStartBitMask);
bool successfullyInsertedNewClientEntry =
_clientByOperationId.insert({lease.start, client}).second;
invariant(successfullyInsertedNewClientEntry,
"Attempted to overwrite an existing client assoicated with this OperationId.");
if (oldLease) {
VERIFY_LEASE_START(oldLease->start, _leaseStartBitMask);
_clientByOperationId.erase(oldLease->start);
_pool->releaseLease(lk, *oldLease);
}
return lease;
};
auto& state = getClientState(client);
if (MONGO_unlikely(state.unused == 0)) {
state.unused = _leaseSize;
state.lease = getLease(state.isInitialized ? &(state.lease) : nullptr);
state.nextId = state.lease.start;
state.isInitialized = true;
}
--state.unused;
return state.nextId++;
}
void OperationIdManager::eraseClientFromMap(Client* client) {
auto& state = getClientState(client);
if (state.isInitialized) {
std::lock_guard lk(_mutex);
VERIFY_LEASE_START(state.lease.start, _leaseStartBitMask);
auto numErased = _clientByOperationId.erase(state.lease.start);
invariant(numErased == 1);
_pool->releaseLease(lk, state.lease);
state.isInitialized = false;
}
}
ClientLock OperationIdManager::findAndLockClient(OperationId id) const {
stdx::lock_guard lk(_mutex);
auto it = _clientByOperationId.find(id & _leaseStartBitMask);
if (it == _clientByOperationId.end()) {
return {};
}
ClientLock lc(it->second);
// Confirm that the provided id matches that of the client's active opCtx.
if (auto opCtx = lc->getOperationContext(); opCtx && opCtx->getOpID() == id) {
return lc;
}
return {};
}
void OperationIdManager::setLeaseSize_forTest(size_t newSize) {
invariant(TestingProctor::instance().isEnabled());
invariant((newSize & (newSize - 1)) == 0, "Thew new lease size must be a power of 2");
_leaseSize = newSize;
_leaseStartBitMask = ~(_leaseSize - 1);
_pool->setLeaseSize_forTest(newSize);
}
} // namespace mongo
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