path: root/src/mongo/db/commands/get_last_error.cpp

/**
 *    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.
 */

#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand

#include "mongo/platform/basic.h"

#include "mongo/db/client.h"
#include "mongo/db/command_generic_argument.h"
#include "mongo/db/commands.h"
#include "mongo/db/curop.h"
#include "mongo/db/field_parser.h"
#include "mongo/db/lasterror.h"
#include "mongo/db/repl/bson_extract_optime.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/db/repl/replication_coordinator.h"
#include "mongo/db/write_concern.h"
#include "mongo/logv2/log.h"
#include "mongo/util/debug_util.h"

namespace mongo {
namespace {

using std::string;
using std::stringstream;

/*
 * Resets any errors so that getLastError comes back clean.
 *
 * Useful before performing a long series of operations where we want to see if any of the
 * operations triggered an error, but we don't want to check after as op, to avoid a round trip.
 *
 * WARNING: This command is deprecated and will be removed in v4.6. (TODO SERVER-47817)
 */
class CmdResetErrorDeprecated : public BasicCommand {
public:
    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }
    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }
    virtual void addRequiredPrivileges(const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) const {}  // No auth required

    bool requiresAuth() const override {
        return false;
    }

    std::string help() const override {
        return "WARNING: This command is deprecated. Resets error state";
    }
    CmdResetErrorDeprecated() : BasicCommand("resetError", "reseterror") {}
    bool run(OperationContext* opCtx,
             const string& db,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) {
        if (_sampler.tick()) {
            LOGV2_WARNING(47187009, "The resetError command is deprecated.");
        }
        LastError::get(opCtx->getClient()).reset();
        return true;
    }

private:
    // Used to log occasional deprecation warnings when this command is invoked.
    Rarely _sampler;
} cmdResetErrorDeprecated;

class CmdGetLastError : public ErrmsgCommandDeprecated {
public:
    CmdGetLastError() : ErrmsgCommandDeprecated("getLastError", "getlasterror") {}
    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }
    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }
    virtual void addRequiredPrivileges(const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) const {}  // No auth required

    bool requiresAuth() const override {
        return false;
    }

    std::string help() const override {
        return "return error status of the last operation on this connection\n"
               "options:\n"
               "  { fsync:true } - fsync before returning, or wait for journal commit if running "
               "with --journal\n"
               "  { j:true } - wait for journal commit if running with --journal\n"
               "  { w:n } - await replication to n servers (including self) before returning\n"
               "  { w:'majority' } - await replication to majority of set\n"
               "  { wtimeout:m} - timeout for w in m milliseconds";
    }

    bool errmsgRun(OperationContext* opCtx,
                   const string& dbname,
                   const BSONObj& cmdObj,
                   string& errmsg,
                   BSONObjBuilder& result) {
        //
        // Correct behavior here is very finicky.
        //
        // 1.  The first step is to append the error that occurred on the previous operation.
        // This adds an "err" field to the command, which is *not* the command failing.
        //
        // 2.  Next we parse and validate write concern options.  If these options are invalid
        // the command fails no matter what, even if we actually had an error earlier.  The
        // reason for checking here is to match legacy behavior on these kind of failures -
        // we'll still get an "err" field for the write error.
        //
        // 3.  If we had an error on the previous operation, we then return immediately.
        //
        // 4.  Finally, we actually enforce the write concern.  All errors *except* timeout are
        // reported with ok : 0.0, to match legacy behavior.
        //
        // There is a special case when "wOpTime" and "wElectionId" are explicitly provided by
        // the client (mongos) - in this case we *only* enforce the write concern if it is
        // valid.
        //
        // We always need to either report "err" (if ok : 1) or "errmsg" (if ok : 0), even if
        // err is null.
        //

        LastError* le = &LastError::get(opCtx->getClient());
        le->disable();

        // Always append lastOp and connectionId
        Client& c = *opCtx->getClient();
        auto replCoord = repl::ReplicationCoordinator::get(opCtx);
        if (replCoord->getReplicationMode() == repl::ReplicationCoordinator::modeReplSet) {
            const repl::OpTime lastOp = repl::ReplClientInfo::forClient(c).getLastOp();
            if (!lastOp.isNull()) {
                lastOp.append(&result, "lastOp");
            }
        }

        // for sharding; also useful in general for debugging
        result.appendNumber("connectionId", c.getConnectionId());

        repl::OpTime lastOpTime;
        bool lastOpTimePresent = true;
        const BSONElement opTimeElement = cmdObj["wOpTime"];
        if (opTimeElement.eoo()) {
            lastOpTimePresent = false;
            lastOpTime = repl::ReplClientInfo::forClient(c).getLastOp();
        } else if (opTimeElement.type() == bsonTimestamp) {
            lastOpTime = repl::OpTime(opTimeElement.timestamp(), repl::OpTime::kUninitializedTerm);
        } else if (opTimeElement.type() == Date) {
            lastOpTime =
                repl::OpTime(Timestamp(opTimeElement.date()), repl::OpTime::kUninitializedTerm);
        } else if (opTimeElement.type() == Object) {
            Status status = bsonExtractOpTimeField(cmdObj, "wOpTime", &lastOpTime);
            if (!status.isOK()) {
                result.append("badGLE", cmdObj);
                return CommandHelpers::appendCommandStatusNoThrow(result, status);
            }
        } else {
            uasserted(ErrorCodes::TypeMismatch,
                      str::stream() << "Expected \"wOpTime\" field in getLastError to "
                                       "have type Date, Timestamp, or OpTime but found type "
                                    << typeName(opTimeElement.type()));
        }


        OID electionId;
        BSONField<OID> wElectionIdField("wElectionId");
        FieldParser::FieldState extracted =
            FieldParser::extract(cmdObj, wElectionIdField, &electionId, &errmsg);
        if (!extracted) {
            result.append("badGLE", cmdObj);
            CommandHelpers::appendSimpleCommandStatus(result, false, errmsg);
            return false;
        }

        bool electionIdPresent = extracted != FieldParser::FIELD_NONE;
        bool errorOccurred = false;

        // Errors aren't reported when wOpTime is used
        if (!lastOpTimePresent) {
            if (le->getNPrev() != 1) {
                errorOccurred = LastError::noError.appendSelf(result, false);
            } else {
                errorOccurred = le->appendSelf(result, false);
            }
        }

        BSONObj writeConcernDoc = ([&] {
            BSONObjBuilder bob;
            for (auto&& elem : cmdObj) {
                if (!isGenericArgument(elem.fieldNameStringData()))
                    bob.append(elem);
            }
            return bob.obj();
        }());

        // Use the default options if we have no gle options aside from wOpTime/wElectionId
        const int nFields = writeConcernDoc.nFields();
        bool useDefaultGLEOptions = (nFields == 1) || (nFields == 2 && lastOpTimePresent) ||
            (nFields == 3 && lastOpTimePresent && electionIdPresent);

        WriteConcernOptions writeConcern;

        if (useDefaultGLEOptions) {
            writeConcern = repl::ReplicationCoordinator::get(opCtx)->getGetLastErrorDefault();
        }

        auto sw = WriteConcernOptions::parse(writeConcernDoc);
        Status status = sw.getStatus();

        //
        // Validate write concern no matter what, this matches 2.4 behavior
        //
        if (status.isOK()) {
            writeConcern = sw.getValue();
            status = validateWriteConcern(opCtx, writeConcern);
        }

        if (!status.isOK()) {
            result.append("badGLE", writeConcernDoc);
            return CommandHelpers::appendCommandStatusNoThrow(result, status);
        }

        // Don't wait for replication if there was an error reported - this matches 2.4 behavior
        if (errorOccurred) {
            dassert(!lastOpTimePresent);
            return true;
        }

        // No error occurred, so we won't duplicate these fields with write concern errors
        dassert(result.asTempObj()["err"].eoo());
        dassert(result.asTempObj()["code"].eoo());

        // If we got an electionId, make sure it matches
        if (electionIdPresent) {
            if (repl::ReplicationCoordinator::get(opCtx)->getReplicationMode() !=
                repl::ReplicationCoordinator::modeReplSet) {
                // Ignore electionIds of 0 from mongos.
                if (electionId != OID()) {
                    errmsg = "wElectionId passed but no replication active";
                    result.append("code", ErrorCodes::BadValue);
                    result.append("codeName", ErrorCodes::errorString(ErrorCodes::BadValue));
                    return false;
                }
            } else {
                if (electionId != repl::ReplicationCoordinator::get(opCtx)->getElectionId()) {
                    LOGV2_DEBUG(20476,
                                3,
                                "OID passed in is {passedOID}, but our id is {ourOID}",
                                "OID mismatch during election",
                                "passedOID"_attr = electionId,
                                "ourOID"_attr =
                                    repl::ReplicationCoordinator::get(opCtx)->getElectionId());
                    errmsg = "election occurred after write";
                    result.append("code", ErrorCodes::WriteConcernFailed);
                    result.append("codeName",
                                  ErrorCodes::errorString(ErrorCodes::WriteConcernFailed));
                    return false;
                }
            }
        }

        {
            stdx::lock_guard<Client> lk(*opCtx->getClient());
            CurOp::get(opCtx)->setMessage_inlock("waiting for write concern");
        }

        WriteConcernResult wcResult;
        status = waitForWriteConcern(opCtx, lastOpTime, writeConcern, &wcResult);
        // getLastError command returns a document that contains the writtenTo array. So we compute
        // the writtenTo array here if we have waited for replication before. The call to
        // getHostsWrittenTo needs to lock the ReplicationCoordinator mutex to guard against
        // topology changes. Thus, we only compute this array here for the getLastError command
        // (instead of in waitForWriteConcern for every single write) to avoid a serialization point
        // for all writes.
        if (!lastOpTime.isNull() && writeConcern.needToWaitForOtherNodes()) {
            wcResult.writtenTo = replCoord->getHostsWrittenTo(
                lastOpTime,
                replCoord->populateUnsetWriteConcernOptionsSyncMode(writeConcern).syncMode ==
                    WriteConcernOptions::SyncMode::JOURNAL);
        }
        wcResult.appendTo(&result);

        // For backward compatibility with 2.4, wtimeout returns ok : 1.0
        if (wcResult.wTimedOut) {
            dassert(!wcResult.err.empty());  // so we always report err
            dassert(!status.isOK());
            result.append("errmsg", "timed out waiting for slaves");
            result.append("code", status.code());
            result.append("codeName", ErrorCodes::errorString(status.code()));
            return true;
        }

        return CommandHelpers::appendCommandStatusNoThrow(result, status);
    }

} cmdGetLastError;

}  // namespace
}  // namespace mongo