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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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kNetwork
#include "mongo/platform/basic.h"
#include "mongo/transport/service_state_machine.h"
#include "mongo/db/client.h"
#include "mongo/db/dbmessage.h"
#include "mongo/db/stats/counters.h"
#include "mongo/stdx/memory.h"
#include "mongo/transport/message_compressor_manager.h"
#include "mongo/transport/service_entry_point.h"
#include "mongo/transport/session.h"
#include "mongo/transport/ticket.h"
#include "mongo/transport/transport_layer.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/concurrency/idle_thread_block.h"
#include "mongo/util/concurrency/thread_name.h"
#include "mongo/util/debug_util.h"
#include "mongo/util/exit.h"
#include "mongo/util/log.h"
#include "mongo/util/net/message.h"
#include "mongo/util/net/socket_exception.h"
#include "mongo/util/net/thread_idle_callback.h"
#include "mongo/util/quick_exit.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
namespace {
// Set up proper headers for formatting an exhaust request, if we need to
bool setExhaustMessage(Message* m, const DbResponse& dbresponse) {
MsgData::View header = dbresponse.response.header();
QueryResult::View qr = header.view2ptr();
long long cursorid = qr.getCursorId();
if (!cursorid) {
return false;
}
invariant(dbresponse.exhaustNS.size() && dbresponse.exhaustNS[0]);
auto ns = dbresponse.exhaustNS; // m->reset() will free this so we must cache a copy
m->reset();
// Rebuild out the response.
BufBuilder b(512);
b.appendNum(static_cast<int>(0) /* size set later in setLen() */);
b.appendNum(header.getId()); // message id
b.appendNum(header.getResponseToMsgId()); // in response to
b.appendNum(static_cast<int>(dbGetMore)); // opCode is OP_GET_MORE
b.appendNum(static_cast<int>(0)); // Must be ZERO (reserved)
b.appendStr(ns); // Namespace
b.appendNum(static_cast<int>(0)); // ntoreturn
b.appendNum(cursorid); // cursor id from the OP_REPLY
MsgData::View(b.buf()).setLen(b.len());
m->setData(b.release());
return true;
}
} // namespace
using transport::TransportLayer;
ServiceStateMachine::ServiceStateMachine(ServiceContext* svcContext,
transport::SessionHandle session,
bool sync)
: _state{State::Source},
_sep{svcContext->getServiceEntryPoint()},
_sync(sync),
_dbClient{svcContext->makeClient("conn", std::move(session))},
_dbClientPtr{_dbClient.get()},
_threadName{str::stream() << "conn" << _dbClient->session()->id()},
_currentOwningThread{stdx::this_thread::get_id()} {}
const transport::SessionHandle& ServiceStateMachine::session() const {
// The _dbClientPtr should always point to our Client which should always own our SessionHandle
return _dbClientPtr->session();
}
void ServiceStateMachine::sourceCallback(Status status) {
// Make sure we just called sourceMessage();
invariant(_state == State::SourceWait);
auto remote = session()->remote();
if (status.isOK()) {
_state = State::Process;
} else if (ErrorCodes::isInterruption(status.code()) ||
ErrorCodes::isNetworkError(status.code())) {
LOG(2) << "Session from " << remote << " encountered a network error during SourceMessage";
_state = State::EndSession;
} else if (status == TransportLayer::TicketSessionClosedStatus) {
// Our session may have been closed internally.
LOG(2) << "Session from " << remote << " was closed internally during SourceMessage";
_state = State::EndSession;
} else {
log() << "Error receiving request from client: " << status << ". Ending connection from "
<< remote << " (connection id: " << session()->id() << ")";
_state = State::EndSession;
}
// In asyncronous mode this is the entrypoint back into the database from the network layer
// after a message has been received, so we want to call runNext() to process the message.
//
// In synchronous mode, runNext() will fall through to call processMessage() so we avoid
// the recursive call.
if (!_sync)
return runNext();
}
void ServiceStateMachine::sinkCallback(Status status) {
invariant(_state == State::SinkWait);
if (!status.isOK()) {
log() << "Error sending response to client: " << status << ". Ending connection from "
<< session()->remote() << " (connection id: " << session()->id() << ")";
_state = State::EndSession;
} else if (inExhaust) {
_state = State::Process;
} else {
_state = State::Source;
}
return scheduleNext();
}
void ServiceStateMachine::processMessage() {
// This may have been called just after a failure to source a message, in which case this
// should return early so the session can be cleaned up.
if (_state != State::Process) {
return;
}
invariant(!_inMessage.empty());
auto& compressorMgr = MessageCompressorManager::forSession(session());
if (_inMessage.operation() == dbCompressed) {
auto swm = compressorMgr.decompressMessage(_inMessage);
uassertStatusOK(swm.getStatus());
_inMessage = swm.getValue();
wasCompressed = true;
} else {
wasCompressed = false;
}
networkCounter.hitLogicalIn(_inMessage.size());
// 2. Pass sourced Message to handler to generate response.
auto opCtx = cc().makeOperationContext();
// The handleRequest is implemented in a subclass for mongod/mongos and actually all the
// database work for this request.
DbResponse dbresponse = _sep->handleRequest(opCtx.get(), _inMessage);
// opCtx must be destroyed here so that the operation cannot show
// up in currentOp results after the response reaches the client
opCtx.reset();
// 3. Format our response, if we have one
Message& toSink = dbresponse.response;
if (!toSink.empty()) {
toSink.header().setId(nextMessageId());
toSink.header().setResponseToMsgId(_inMessage.header().getId());
// If this is an exhaust cursor, don't source more Messages
if (dbresponse.exhaustNS.size() > 0 && setExhaustMessage(&_inMessage, dbresponse)) {
inExhaust = true;
} else {
inExhaust = false;
_inMessage.reset();
}
networkCounter.hitLogicalOut(toSink.size());
if (wasCompressed) {
auto swm = compressorMgr.compressMessage(toSink);
uassertStatusOK(swm.getStatus());
toSink = swm.getValue();
}
// 4. Sink our response to the client
auto ticket = session()->sinkMessage(toSink);
_state = State::SinkWait;
if (_sync) {
sinkCallback(session()->getTransportLayer()->wait(std::move(ticket)));
} else {
session()->getTransportLayer()->asyncWait(
std::move(ticket), [this](Status status) { sinkCallback(status); });
}
} else {
_state = State::Source;
_inMessage.reset();
return scheduleNext();
}
}
/*
* This class wraps up the logic for swapping/unswapping the Client during runNext().
*/
class ServiceStateMachine::ThreadGuard {
ThreadGuard(ThreadGuard&) = delete;
ThreadGuard& operator=(ThreadGuard&) = delete;
public:
explicit ThreadGuard(ServiceStateMachine* ssm)
: _ssm{ssm},
_haveTakenOwnership{!_ssm->_isOwned.test_and_set()},
_oldThreadName{getThreadName().toString()} {
const auto currentOwningThread = _ssm->_currentOwningThread.load();
const auto currentThreadId = stdx::this_thread::get_id();
// If this is true, then we are the "owner" of the Client and we should swap the
// client/thread name before doing any work.
if (_haveTakenOwnership) {
_ssm->_currentOwningThread.store(currentThreadId);
// Set up the thread name
setThreadName(_ssm->_threadName);
// These are sanity checks to make sure that the Client is what we expect it to be
invariant(!haveClient());
invariant(_ssm->_dbClient.get() == _ssm->_dbClientPtr);
// Swap the current Client so calls to cc() work as expected
Client::setCurrent(std::move(_ssm->_dbClient));
} else if (currentOwningThread != currentThreadId) {
// If the currentOwningThread does not equal the currentThreadId, then another thread
// currently "owns" the Client and we should reschedule ourself.
_okayToRunNext = false;
}
}
~ThreadGuard() {
if (!_haveTakenOwnership)
return;
if (haveClient()) {
_ssm->_dbClient = Client::releaseCurrent();
}
setThreadName(_oldThreadName);
_ssm->_isOwned.clear();
}
void dismiss() {
_haveTakenOwnership = false;
}
explicit operator bool() const {
return _okayToRunNext;
}
private:
ServiceStateMachine* _ssm;
bool _haveTakenOwnership;
const std::string _oldThreadName;
bool _okayToRunNext = true;
};
void ServiceStateMachine::runNext() {
ThreadGuard guard(this);
if (!guard)
return scheduleNext();
// Make sure the current Client got set correctly
invariant(Client::getCurrent() == _dbClientPtr);
try {
switch (_state) {
case State::Source: {
invariant(_inMessage.empty());
auto ticket = session()->sourceMessage(&_inMessage);
_state = State::SourceWait;
if (_sync) {
MONGO_IDLE_THREAD_BLOCK;
sourceCallback(session()->getTransportLayer()->wait(std::move(ticket)));
} else {
session()->getTransportLayer()->asyncWait(
std::move(ticket), [this](Status status) { sourceCallback(status); });
break;
}
}
case State::Process:
processMessage();
break;
case State::EndSession:
// This will get handled below in an if statement. That way if an error occurs
// you don't have to call runNext() again to clean up the session.
break;
default:
MONGO_UNREACHABLE;
}
if (_state == State::EndSession) {
guard.dismiss();
endSession();
}
if ((_counter++ & 0xf) == 0) {
markThreadIdle();
};
return;
} catch (const AssertionException& e) {
log() << "AssertionException handling request, closing client connection: " << e;
} catch (const SocketException& e) {
log() << "SocketException handling request, closing client connection: " << e;
} catch (const DBException& e) {
// must be right above std::exception to avoid catching subclasses
log() << "DBException handling request, closing client connection: " << e;
} catch (const std::exception& e) {
error() << "Uncaught std::exception: " << e.what() << ", terminating";
quickExit(EXIT_UNCAUGHT);
}
_state = State::EndSession;
guard.dismiss();
endSession();
}
// TODO: Right now this is a noop because we only run in synchronous mode. When an async
// TransportLayer is written, this will call the serviceexecutor to schedule calls to runNext().
void ServiceStateMachine::scheduleNext() {}
void ServiceStateMachine::endSession() {
auto tl = session()->getTransportLayer();
_inMessage.reset();
auto remote = session()->remote();
Client::releaseCurrent();
if (!serverGlobalParams.quiet.load()) {
auto conns = tl->sessionStats().numOpenSessions;
const char* word = (conns == 1 ? " connection" : " connections");
log() << "end connection " << remote << " (" << conns << word << " now open)";
}
_state = State::Ended;
}
std::ostream& operator<<(std::ostream& stream, const ServiceStateMachine::State& state) {
switch (state) {
case ServiceStateMachine::State::Source:
stream << "source";
break;
case ServiceStateMachine::State::SourceWait:
stream << "sourceWait";
break;
case ServiceStateMachine::State::Process:
stream << "process";
break;
case ServiceStateMachine::State::SinkWait:
stream << "sinkWait";
break;
case ServiceStateMachine::State::EndSession:
stream << "endSession";
break;
case ServiceStateMachine::State::Ended:
stream << "ended";
break;
}
return stream;
}
} // namespace mongo
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