path: root/src/mongo/client/dbclientcursor.cpp

// dbclient.cpp - connect to a Mongo database as a database, from C++

/*    Copyright 2009 10gen 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/client/dbclientcursor.h"

#include "mongo/client/connpool.h"
#include "mongo/db/dbmessage.h"
#include "mongo/db/namespace_string.h"
#include "mongo/rpc/factory.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/rpc/metadata.h"
#include "mongo/rpc/request_builder_interface.h"
#include "mongo/s/stale_exception.h"
#include "mongo/stdx/memory.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::unique_ptr;
using std::endl;
using std::string;
using std::vector;

namespace {
/**
 * This code is mostly duplicated from DBClientWithCommands::runCommand. It may not
 * be worth de-duplicating as this codepath will eventually be removed anyway.
 */
Message assembleCommandRequest(DBClientWithCommands* cli,
                               StringData database,
                               int legacyQueryOptions,
                               BSONObj legacyQuery) {
    // TODO: Rewrite this to a common utility shared between this and DBClientMultiCommand.

    // Can be an OP_COMMAND or OP_QUERY message.
    auto requestBuilder =
        rpc::makeRequestBuilder(cli->getClientRPCProtocols(), cli->getServerRPCProtocols());

    BSONObj upconvertedCommand;
    BSONObj upconvertedMetadata;

    std::tie(upconvertedCommand, upconvertedMetadata) =
        uassertStatusOK(rpc::upconvertRequestMetadata(std::move(legacyQuery), legacyQueryOptions));

    BSONObjBuilder metadataBob;
    metadataBob.appendElements(upconvertedMetadata);
    if (cli->getRequestMetadataWriter()) {
        uassertStatusOK(cli->getRequestMetadataWriter()(&metadataBob, cli->getServerAddress()));
    }

    requestBuilder->setDatabase(database);
    // We need to get the command name from the upconverted command as it may have originally
    // been wrapped.
    requestBuilder->setCommandName(upconvertedCommand.firstElementFieldName());
    requestBuilder->setCommandArgs(std::move(upconvertedCommand));
    requestBuilder->setMetadata(metadataBob.done());

    return requestBuilder->done();
}

}  // namespace

int DBClientCursor::nextBatchSize() {
    if (nToReturn == 0)
        return batchSize;

    if (batchSize == 0)
        return nToReturn;

    return batchSize < nToReturn ? batchSize : nToReturn;
}

void DBClientCursor::_assembleInit(Message& toSend) {
    // If we haven't gotten a cursorId yet, we need to issue a new query or command.
    if (!cursorId) {
        // 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);

        if (_isCommand && hasValidNToReturnForCommand && hasValidFlagsForCommand) {
            toSend = assembleCommandRequest(_client, nsToDatabaseSubstring(ns), opts, query);
            return;
        }
        assembleQueryRequest(ns, query, nextBatchSize(), nToSkip, fieldsToReturn, opts, toSend);
        return;
    }
    // Assemble a legacy getMore request.
    BufBuilder b;
    b.appendNum(opts);
    b.appendStr(ns);
    b.appendNum(nToReturn);
    b.appendNum(cursorId);
    toSend.setData(dbGetMore, b.buf(), b.len());
}

bool DBClientCursor::init() {
    Message toSend;
    _assembleInit(toSend);
    verify(_client);
    if (!_client->call(toSend, batch.m, false, &_originalHost)) {
        // log msg temp?
        log() << "DBClientCursor::init call() failed" << endl;
        return false;
    }
    if (batch.m.empty()) {
        // log msg temp?
        log() << "DBClientCursor::init message from call() was empty" << endl;
        return false;
    }
    dataReceived();
    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(toSend);
    _client->say(toSend, isRetry, &_originalHost);
}

bool DBClientCursor::initLazyFinish(bool& retry) {
    bool recvd = _client->recv(batch.m);

    // If we get a bad response, return false
    if (!recvd || batch.m.empty()) {
        if (!recvd)
            log() << "DBClientCursor::init lazy say() failed" << endl;
        if (batch.m.empty())
            log() << "DBClientCursor::init message from say() was empty" << endl;

        _client->checkResponse(NULL, -1, &retry, &_lazyHost);

        return false;
    }

    dataReceived(retry, _lazyHost);

    return !retry;
}

void DBClientCursor::requestMore() {
    verify(cursorId && batch.pos == batch.nReturned);

    if (haveLimit) {
        nToReturn -= batch.nReturned;
        verify(nToReturn > 0);
    }
    BufBuilder b;
    b.appendNum(opts);
    b.appendStr(ns);
    b.appendNum(nextBatchSize());
    b.appendNum(cursorId);

    Message toSend;
    toSend.setData(dbGetMore, b.buf(), b.len());
    Message response;

    if (_client) {
        _client->call(toSend, response);
        this->batch.m = std::move(response);
        dataReceived();
    } else {
        verify(_scopedHost.size());
        ScopedDbConnection conn(_scopedHost);
        conn->call(toSend, response);
        _client = conn.get();
        ON_BLOCK_EXIT([this] { _client = nullptr; });
        this->batch.m = std::move(response);
        dataReceived();
        conn.done();
    }
}

/** with QueryOption_Exhaust, the server just blasts data at us (marked at end with cursorid==0). */
void DBClientCursor::exhaustReceiveMore() {
    verify(cursorId && batch.pos == batch.nReturned);
    verify(!haveLimit);
    Message response;
    verify(_client);
    if (!_client->recv(response)) {
        uasserted(16465, "recv failed while exhausting cursor");
    }
    batch.m = std::move(response);
    dataReceived();
}

void DBClientCursor::commandDataReceived() {
    int op = batch.m.operation();
    invariant(op == opReply || op == dbCommandReply);

    batch.nReturned = 1;
    batch.pos = 0;

    auto commandReply = rpc::makeReply(&batch.m);

    auto commandStatus = getStatusFromCommandResult(commandReply->getCommandReply());

    if (ErrorCodes::SendStaleConfig == commandStatus) {
        throw RecvStaleConfigException("stale config in DBClientCursor::dataReceived()",
                                       commandReply->getCommandReply());
    } else if (!commandStatus.isOK()) {
        wasError = true;
    }

    if (_client->getReplyMetadataReader()) {
        uassertStatusOK(_client->getReplyMetadataReader()(commandReply->getMetadata(),
                                                          _client->getServerAddress()));
    }

    // HACK: If we got an OP_COMMANDREPLY, take the reply object
    // and shove it in to an OP_REPLY message.
    if (op == dbCommandReply) {
        // Need to take ownership here as we destroy the underlying message.
        BSONObj reply = commandReply->getCommandReply().getOwned();
        batch.m.reset();
        replyToQuery(0, batch.m, reply);
    }

    QueryResult::View qr = batch.m.singleData().view2ptr();
    batch.data = qr.data();
}

void DBClientCursor::dataReceived(bool& retry, string& host) {
    // If this is a reply to our initial command request.
    if (_isCommand && cursorId == 0) {
        commandDataReceived();
        return;
    }

    QueryResult::View qr = batch.m.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(13127,
                      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();
    }

    batch.nReturned = qr.getNReturned();
    batch.pos = 0;
    batch.data = qr.data();

    _client->checkResponse(batch.data, batch.nReturned, &retry, &host);  // watches for "not master"

    if (qr.getResultFlags() & ResultFlag_ShardConfigStale) {
        BSONObj error;
        verify(peekError(&error));
        throw RecvStaleConfigException(
            (string) "stale config on lazy receive" + causedBy(getErrField(error)), error);
    }

    /* 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() {
    _assertIfNull();

    if (!_putBack.empty())
        return true;

    if (haveLimit && batch.pos >= nToReturn)
        return false;

    if (batch.pos < batch.nReturned)
        return true;

    if (cursorId == 0)
        return false;

    requestMore();
    return batch.pos < batch.nReturned;
}

BSONObj DBClientCursor::next() {
    DEV _assertIfNull();
    if (!_putBack.empty()) {
        BSONObj ret = _putBack.top();
        _putBack.pop();
        return ret;
    }

    uassert(13422, "DBClientCursor next() called but more() is false", batch.pos < batch.nReturned);

    batch.pos++;
    BSONObj o(batch.data);
    batch.data += o.objsize();
    /* todo would be good to make data null at end of batch for safety */
    return o;
}

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) {
        auto code = o["code"].numberInt();
        if (!code) {
            code = ErrorCodes::UnknownError;
        }
        uasserted(code, o.firstElement().str());
    }

    return o;
}

void DBClientCursor::peek(vector<BSONObj>& v, int atMost) {
    int m = atMost;

    /*
    for( stack<BSONObj>::iterator i = _putBack.begin(); i != _putBack.end(); i++ ) {
        if( m == 0 )
            return;
        v.push_back(*i);
        m--;
        n++;
    }
    */

    int p = batch.pos;
    const char* d = batch.data;
    while (m && p < batch.nReturned) {
        BSONObj o(d);
        d += o.objsize();
        p++;
        m--;
        v.push_back(o);
    }
}

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 = 0;
    _lazyHost = "";
}

DBClientCursor::DBClientCursor(DBClientBase* client,
                               const std::string& ns,
                               const BSONObj& query,
                               int nToReturn,
                               int nToSkip,
                               const BSONObj* fieldsToReturn,
                               int queryOptions,
                               int batchSize)
    : DBClientCursor(client,
                     ns,
                     query,
                     0,  // cursorId
                     nToReturn,
                     nToSkip,
                     fieldsToReturn,
                     queryOptions,
                     batchSize) {}

DBClientCursor::DBClientCursor(DBClientBase* client,
                               const std::string& ns,
                               long long cursorId,
                               int nToReturn,
                               int queryOptions)
    : DBClientCursor(client,
                     ns,
                     BSONObj(),  // query
                     cursorId,
                     nToReturn,
                     0,        // nToSkip
                     nullptr,  // fieldsToReturn
                     queryOptions,
                     0) {}  // batchSize

DBClientCursor::DBClientCursor(DBClientBase* client,
                               const std::string& ns,
                               const BSONObj& query,
                               long long cursorId,
                               int nToReturn,
                               int nToSkip,
                               const BSONObj* fieldsToReturn,
                               int queryOptions,
                               int batchSize)
    : _client(client),
      _originalHost(_client->getServerAddress()),
      ns(ns),
      _isCommand(nsIsFull(ns) ? nsToCollectionSubstring(ns) == "$cmd" : false),
      query(query),
      nToReturn(nToReturn),
      haveLimit(nToReturn > 0 && !(queryOptions & QueryOption_CursorTailable)),
      nToSkip(nToSkip),
      fieldsToReturn(fieldsToReturn),
      opts(queryOptions),
      batchSize(batchSize == 1 ? 2 : batchSize),
      resultFlags(0),
      cursorId(cursorId),
      _ownCursor(true),
      wasError(false) {}

DBClientCursor::~DBClientCursor() {
    kill();
}

void DBClientCursor::kill() {
    DESTRUCTOR_GUARD(

        if (cursorId && _ownCursor && !inShutdown()) {
            if (_client) {
                _client->killCursor(cursorId);
            } else {
                verify(_scopedHost.size());
                ScopedDbConnection conn(_scopedHost);
                conn->killCursor(cursorId);
                conn.done();
            }
        }

        );

    // Mark this cursor as dead since we can't do any getMores.
    cursorId = 0;
}


}  // namespace mongo