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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.
*/
/**
* Connect to a Mongo database as a database, from C++.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kNetwork
#include "mongo/platform/basic.h"
#include "mongo/client/dbclient_cursor.h"
#include <memory>
#include "mongo/client/connpool.h"
#include "mongo/db/client.h"
#include "mongo/db/dbmessage.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/query/cursor_response.h"
#include "mongo/db/query/getmore_request.h"
#include "mongo/db/query/query_request.h"
#include "mongo/rpc/factory.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/rpc/metadata.h"
#include "mongo/rpc/object_check.h"
#include "mongo/s/stale_exception.h"
#include "mongo/util/bufreader.h"
#include "mongo/util/debug_util.h"
#include "mongo/util/destructor_guard.h"
#include "mongo/util/exit.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
using std::endl;
using std::string;
using std::unique_ptr;
using std::vector;
namespace {
Message assembleCommandRequest(DBClientBase* cli,
StringData database,
int legacyQueryOptions,
BSONObj legacyQuery) {
auto request = rpc::upconvertRequest(database, std::move(legacyQuery), legacyQueryOptions);
if (cli->getRequestMetadataWriter()) {
BSONObjBuilder bodyBob(std::move(request.body));
auto opCtx = (haveClient() ? cc().getOperationContext() : nullptr);
uassertStatusOK(cli->getRequestMetadataWriter()(opCtx, &bodyBob));
request.body = bodyBob.obj();
}
return rpc::messageFromOpMsgRequest(
cli->getClientRPCProtocols(), cli->getServerRPCProtocols(), std::move(request));
}
} // namespace
int DBClientCursor::nextBatchSize() {
if (nToReturn == 0)
return batchSize;
if (batchSize == 0)
return nToReturn;
return batchSize < nToReturn ? batchSize : nToReturn;
}
Message DBClientCursor::_assembleInit() {
if (cursorId) {
return _assembleGetMore();
}
// If we haven't gotten a cursorId yet, we need to issue a new query or command.
if (_isCommand) {
// HACK:
// Unfortunately, this code is used by the shell to run commands,
// so we need to allow the shell to send invalid options so that we can
// test that the server rejects them. Thus, to allow generating commands with
// invalid options, we validate them here, and fall back to generating an OP_QUERY
// through assembleQueryRequest if the options are invalid.
bool hasValidNToReturnForCommand = (nToReturn == 1 || nToReturn == -1);
bool hasValidFlagsForCommand = !(opts & mongo::QueryOption_Exhaust);
bool hasInvalidMaxTimeMs = query.hasField("$maxTimeMS");
if (hasValidNToReturnForCommand && hasValidFlagsForCommand && !hasInvalidMaxTimeMs) {
return assembleCommandRequest(_client, ns.db(), opts, query);
}
} else if (_useFindCommand) {
// The caller supplies a 'query' object which may have $-prefixed directives in the format
// expected for a legacy OP_QUERY. Therefore, we use the legacy parsing code supplied by
// QueryRequest. When actually issuing the request to the remote node, we will assemble a
// find command.
auto qr = QueryRequest::fromLegacyQuery(_nsOrUuid,
query,
fieldsToReturn ? *fieldsToReturn : BSONObj(),
nToSkip,
nextBatchSize(),
opts);
if (qr.isOK() && !qr.getValue()->isExplain()) {
if (query.getBoolField("$readOnce")) {
// Legacy queries don't handle readOnce.
qr.getValue()->setReadOnce(true);
}
if (query.getBoolField("$_requestResumeToken")) {
// Legacy queries don't handle requestResumeToken.
qr.getValue()->setRequestResumeToken(true);
}
if (query.hasField("$_resumeAfter")) {
// Legacy queries don't handle resumeAfter.
qr.getValue()->setResumeAfter(query.getObjectField("$_resumeAfter"));
}
if (auto replTerm = query[QueryRequest::kTermField]) {
// Legacy queries don't handle term.
qr.getValue()->setReplicationTerm(replTerm.numberLong());
}
if (auto readConcern = query[repl::ReadConcernArgs::kReadConcernFieldName]) {
// Legacy queries don't handle readConcern.
qr.getValue()->setReadConcern(readConcern.Obj());
}
BSONObj cmd = _nsOrUuid.uuid() ? qr.getValue()->asFindCommandWithUuid()
: qr.getValue()->asFindCommand();
if (auto readPref = query["$readPreference"]) {
// QueryRequest doesn't handle $readPreference.
cmd = BSONObjBuilder(std::move(cmd)).append(readPref).obj();
}
return assembleCommandRequest(_client, ns.db(), opts, std::move(cmd));
}
// else use legacy OP_QUERY request.
// Legacy OP_QUERY request does not support UUIDs.
if (_nsOrUuid.uuid()) {
// If there was a problem building the query request, report that.
uassertStatusOK(qr.getStatus());
// Otherwise it must have been explain.
uasserted(50937, "Query by UUID is not supported for explain queries.");
}
}
_useFindCommand = false; // Make sure we handle the reply correctly.
Message toSend;
assembleQueryRequest(ns.ns(), query, nextBatchSize(), nToSkip, fieldsToReturn, opts, toSend);
return toSend;
}
Message DBClientCursor::_assembleGetMore() {
invariant(cursorId);
if (_useFindCommand) {
std::int64_t batchSize = nextBatchSize();
auto gmr = GetMoreRequest(ns,
cursorId,
boost::make_optional(batchSize != 0, batchSize),
boost::make_optional(tailableAwaitData(),
_awaitDataTimeout), // awaitDataTimeout
_term,
_lastKnownCommittedOpTime);
auto msg = assembleCommandRequest(_client, ns.db(), opts, gmr.toBSON());
// Set the exhaust flag if needed.
if (opts & QueryOption_Exhaust && msg.operation() == dbMsg) {
OpMsg::setFlag(&msg, OpMsg::kExhaustSupported);
}
return msg;
} else {
// Assemble a legacy getMore request.
return makeGetMoreMessage(ns.ns(), cursorId, nextBatchSize(), opts);
}
}
bool DBClientCursor::init() {
invariant(!_connectionHasPendingReplies);
Message toSend = _assembleInit();
verify(_client);
Message reply;
try {
_client->call(toSend, reply, true, &_originalHost);
} catch (const DBException&) {
// log msg temp?
log() << "DBClientCursor::init call() failed" << endl;
// We always want to throw on network exceptions.
throw;
}
if (reply.empty()) {
// log msg temp?
log() << "DBClientCursor::init message from call() was empty" << endl;
return false;
}
dataReceived(reply);
return true;
}
void DBClientCursor::initLazy(bool isRetry) {
massert(15875,
"DBClientCursor::initLazy called on a client that doesn't support lazy",
_client->lazySupported());
Message toSend = _assembleInit();
_client->say(toSend, isRetry, &_originalHost);
_lastRequestId = toSend.header().getId();
_connectionHasPendingReplies = true;
}
bool DBClientCursor::initLazyFinish(bool& retry) {
invariant(_connectionHasPendingReplies);
Message reply;
Status recvStatus = _client->recv(reply, _lastRequestId);
_connectionHasPendingReplies = false;
// If we get a bad response, return false
if (!recvStatus.isOK() || reply.empty()) {
if (!recvStatus.isOK())
log() << "DBClientCursor::init lazy say() failed: " << redact(recvStatus) << endl;
if (reply.empty())
log() << "DBClientCursor::init message from say() was empty" << endl;
_client->checkResponse({}, true, &retry, &_lazyHost);
return false;
}
dataReceived(reply, retry, _lazyHost);
return !retry;
}
void DBClientCursor::requestMore() {
// For exhaust queries, once the stream has been initiated we get data blasted to us
// from the remote server, without a need to send any more 'getMore' requests.
const auto isExhaust = opts & QueryOption_Exhaust;
if (isExhaust && (!_useFindCommand || _connectionHasPendingReplies)) {
return exhaustReceiveMore();
}
invariant(!_connectionHasPendingReplies);
verify(cursorId && batch.pos == batch.objs.size());
if (haveLimit) {
nToReturn -= batch.objs.size();
verify(nToReturn > 0);
}
auto doRequestMore = [&] {
Message toSend = _assembleGetMore();
Message response;
_client->call(toSend, response);
dataReceived(response);
};
if (_client)
return doRequestMore();
invariant(_scopedHost.size());
DBClientBase::withConnection_do_not_use(_scopedHost, [&](DBClientBase* conn) {
ON_BLOCK_EXIT([&, origClient = _client] { _client = origClient; });
_client = conn;
doRequestMore();
});
}
/**
* With QueryOption_Exhaust, the server just blasts data at us. The end of a stream is marked with a
* cursor id of 0.
*/
void DBClientCursor::exhaustReceiveMore() {
verify(cursorId);
verify(batch.pos == batch.objs.size());
uassert(40675, "Cannot have limit for exhaust query", !haveLimit);
Message response;
verify(_client);
uassertStatusOK(
_client->recv(response, _lastRequestId).withContext("recv failed while exhausting cursor"));
dataReceived(response);
}
BSONObj DBClientCursor::commandDataReceived(const Message& reply) {
int op = reply.operation();
invariant(op == opReply || op == dbMsg);
// Check if the reply indicates that it is part of an exhaust stream.
const auto isExhaust = OpMsg::isFlagSet(reply, OpMsg::kMoreToCome);
_connectionHasPendingReplies = isExhaust;
if (isExhaust) {
_lastRequestId = reply.header().getId();
}
auto commandReply = _client->parseCommandReplyMessage(_client->getServerAddress(), reply);
auto commandStatus = getStatusFromCommandResult(commandReply->getCommandReply());
if (commandStatus == ErrorCodes::StaleConfig) {
uassertStatusOK(
commandStatus.withContext("stale config in DBClientCursor::dataReceived()"));
} else if (!commandStatus.isOK()) {
wasError = true;
}
return commandReply->getCommandReply().getOwned();
}
void DBClientCursor::dataReceived(const Message& reply, bool& retry, string& host) {
batch.objs.clear();
batch.pos = 0;
// If this is a reply to our initial command request.
if (_isCommand && cursorId == 0) {
batch.objs.push_back(commandDataReceived(reply));
return;
}
if (_useFindCommand) {
cursorId = 0; // Don't try to kill cursor if we get back an error.
auto cr = uassertStatusOK(CursorResponse::parseFromBSON(commandDataReceived(reply)));
cursorId = cr.getCursorId();
uassert(50935,
"Received a getMore response with a cursor id of 0 and the moreToCome flag set.",
!(_connectionHasPendingReplies && cursorId == 0));
ns = cr.getNSS(); // Unlike OP_REPLY, find command can change the ns to use for getMores.
// Store the resume token, if we got one.
_postBatchResumeToken = cr.getPostBatchResumeToken();
batch.objs = cr.releaseBatch();
return;
}
QueryResult::View qr = reply.singleData().view2ptr();
resultFlags = qr.getResultFlags();
if (qr.getResultFlags() & ResultFlag_ErrSet) {
wasError = true;
}
if (qr.getResultFlags() & ResultFlag_CursorNotFound) {
// cursor id no longer valid at the server.
invariant(qr.getCursorId() == 0);
if (!(opts & QueryOption_CursorTailable)) {
uasserted(ErrorCodes::CursorNotFound,
str::stream() << "cursor id " << cursorId << " didn't exist on server.");
}
// 0 indicates no longer valid (dead)
cursorId = 0;
}
if (cursorId == 0 || !(opts & QueryOption_CursorTailable)) {
// only set initially: we don't want to kill it on end of data
// if it's a tailable cursor
cursorId = qr.getCursorId();
}
if (opts & QueryOption_Exhaust) {
// With exhaust mode, each reply after the first claims to be a reply to the previous one
// rather than the initial request.
_connectionHasPendingReplies = (cursorId != 0);
_lastRequestId = reply.header().getId();
}
batch.objs.reserve(qr.getNReturned());
BufReader data(qr.data(), qr.dataLen());
while (static_cast<int>(batch.objs.size()) < qr.getNReturned()) {
if (serverGlobalParams.objcheck) {
batch.objs.push_back(data.read<Validated<BSONObj>>());
} else {
batch.objs.push_back(data.read<BSONObj>());
}
batch.objs.back().shareOwnershipWith(reply.sharedBuffer());
}
uassert(ErrorCodes::InvalidBSON,
"Got invalid reply from external server while reading from cursor",
data.atEof());
_client->checkResponse(batch.objs, false, &retry, &host); // watches for "not master"
if (qr.getResultFlags() & ResultFlag_ShardConfigStale) {
BSONObj error;
verify(peekError(&error));
uasserted(StaleConfigInfo::parseFromCommandError(error), "stale config on lazy receive");
}
/* this assert would fire the way we currently work:
verify( nReturned || cursorId == 0 );
*/
}
/** If true, safe to call next(). Requests more from server if necessary. */
bool DBClientCursor::more() {
if (!_putBack.empty())
return true;
if (haveLimit && static_cast<int>(batch.pos) >= nToReturn)
return false;
if (batch.pos < batch.objs.size())
return true;
if (cursorId == 0)
return false;
requestMore();
return batch.pos < batch.objs.size();
}
BSONObj DBClientCursor::next() {
if (!_putBack.empty()) {
BSONObj ret = _putBack.top();
_putBack.pop();
return ret;
}
uassert(
13422, "DBClientCursor next() called but more() is false", batch.pos < batch.objs.size());
/* todo would be good to make data null at end of batch for safety */
return std::move(batch.objs[batch.pos++]);
}
BSONObj DBClientCursor::nextSafe() {
BSONObj o = next();
// Only convert legacy errors ($err) to exceptions. Otherwise, just return the response and the
// caller will interpret it as a command error.
if (wasError && strcmp(o.firstElementFieldName(), "$err") == 0) {
uassertStatusOK(getStatusFromCommandResult(o));
}
return o;
}
void DBClientCursor::peek(vector<BSONObj>& v, int atMost) {
auto end = atMost >= static_cast<int>(batch.objs.size() - batch.pos)
? batch.objs.end()
: batch.objs.begin() + batch.pos + atMost;
v.insert(v.end(), batch.objs.begin() + batch.pos, end);
}
BSONObj DBClientCursor::peekFirst() {
vector<BSONObj> v;
peek(v, 1);
if (v.size() > 0)
return v[0];
else
return BSONObj();
}
bool DBClientCursor::peekError(BSONObj* error) {
if (!wasError)
return false;
vector<BSONObj> v;
peek(v, 1);
verify(v.size() == 1);
// We check both the legacy error format, and the new error format. hasErrField checks for
// $err, and getStatusFromCommandResult checks for modern errors of the form '{ok: 0.0, code:
// <...>, errmsg: ...}'.
verify(hasErrField(v[0]) || !getStatusFromCommandResult(v[0]).isOK());
if (error)
*error = v[0].getOwned();
return true;
}
void DBClientCursor::attach(AScopedConnection* conn) {
verify(_scopedHost.size() == 0);
verify(conn);
verify(conn->get());
if (conn->get()->type() == ConnectionString::SET) {
if (_lazyHost.size() > 0)
_scopedHost = _lazyHost;
else if (_client)
_scopedHost = _client->getServerAddress();
else
massert(14821,
"No client or lazy client specified, cannot store multi-host connection.",
false);
} else {
_scopedHost = conn->getHost();
}
conn->done();
_client = nullptr;
_lazyHost = "";
}
DBClientCursor::DBClientCursor(DBClientBase* client,
const NamespaceStringOrUUID& nsOrUuid,
const BSONObj& query,
int nToReturn,
int nToSkip,
const BSONObj* fieldsToReturn,
int queryOptions,
int batchSize)
: DBClientCursor(client,
nsOrUuid,
query,
0, // cursorId
nToReturn,
nToSkip,
fieldsToReturn,
queryOptions,
batchSize,
{}) {}
DBClientCursor::DBClientCursor(DBClientBase* client,
const NamespaceStringOrUUID& nsOrUuid,
long long cursorId,
int nToReturn,
int queryOptions,
std::vector<BSONObj> initialBatch)
: DBClientCursor(client,
nsOrUuid,
BSONObj(), // query
cursorId,
nToReturn,
0, // nToSkip
nullptr, // fieldsToReturn
queryOptions,
0,
std::move(initialBatch)) {} // batchSize
DBClientCursor::DBClientCursor(DBClientBase* client,
const NamespaceStringOrUUID& nsOrUuid,
const BSONObj& query,
long long cursorId,
int nToReturn,
int nToSkip,
const BSONObj* fieldsToReturn,
int queryOptions,
int batchSize,
std::vector<BSONObj> initialBatch)
: batch{std::move(initialBatch)},
_client(client),
_originalHost(_client->getServerAddress()),
_nsOrUuid(nsOrUuid),
ns(nsOrUuid.nss() ? *nsOrUuid.nss() : NamespaceString(nsOrUuid.dbname())),
_isCommand(ns.isCommand()),
query(query),
nToReturn(nToReturn),
haveLimit(nToReturn > 0 && !(queryOptions & QueryOption_CursorTailable)),
nToSkip(nToSkip),
fieldsToReturn(fieldsToReturn),
opts(queryOptions & ~QueryOptionLocal_forceOpQuery),
batchSize(batchSize == 1 ? 2 : batchSize),
resultFlags(0),
cursorId(cursorId),
_ownCursor(true),
wasError(false),
_enabledBSONVersion(Validator<BSONObj>::enabledBSONVersion()) {
if (queryOptions & QueryOptionLocal_forceOpQuery) {
// Legacy OP_QUERY does not support UUIDs.
invariant(!_nsOrUuid.uuid());
_useFindCommand = false;
}
}
DBClientCursor::~DBClientCursor() {
kill();
}
void DBClientCursor::kill() {
DESTRUCTOR_GUARD({
if (cursorId && _ownCursor && !globalInShutdownDeprecated()) {
auto killCursor = [&](auto&& conn) {
if (_useFindCommand) {
conn->killCursor(ns, cursorId);
} else {
auto toSend = makeKillCursorsMessage(cursorId);
conn->say(toSend);
}
};
if (_client && !_connectionHasPendingReplies) {
killCursor(_client);
} else {
// Use a side connection to send the kill cursor request.
verify(_scopedHost.size() || (_client && _connectionHasPendingReplies));
DBClientBase::withConnection_do_not_use(
_client ? _client->getServerAddress() : _scopedHost, killCursor);
}
}
});
// Mark this cursor as dead since we can't do any getMores.
cursorId = 0;
}
} // namespace mongo
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