path: root/src/mongo/s/commands/cluster_split_cmd.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.
 */


#include "mongo/platform/basic.h"

#include <string>
#include <vector>

#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/db/field_parser.h"
#include "mongo/logv2/log.h"
#include "mongo/s/catalog_cache.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/cluster_commands_helpers.h"
#include "mongo/s/grid.h"
#include "mongo/s/shard_util.h"

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


namespace mongo {
namespace {

/**
 * Asks the mongod holding this chunk to find a key that approximately divides the specified chunk
 * in two. Throws on error or if the chunk is indivisible.
 */
BSONObj selectMedianKey(OperationContext* opCtx,
                        const ShardId& shardId,
                        const NamespaceString& nss,
                        const ShardKeyPattern& shardKeyPattern,
                        const ChunkVersion& chunkVersion,
                        const ChunkRange& chunkRange) {
    BSONObjBuilder cmd;
    cmd.append("splitVector", nss.ns());
    cmd.append("keyPattern", shardKeyPattern.toBSON());
    chunkRange.append(&cmd);
    cmd.appendBool("force", true);
    chunkVersion.serializeToBSON(ChunkVersion::kShardVersionField, &cmd);

    auto shard = uassertStatusOK(Grid::get(opCtx)->shardRegistry()->getShard(opCtx, shardId));

    auto cmdResponse = uassertStatusOK(
        shard->runCommandWithFixedRetryAttempts(opCtx,
                                                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                "admin",
                                                cmd.obj(),
                                                Shard::RetryPolicy::kIdempotent));

    uassertStatusOK(cmdResponse.commandStatus);

    BSONObjIterator it(cmdResponse.response.getObjectField("splitKeys"));
    if (it.more()) {
        return it.next().Obj().getOwned();
    }

    uasserted(ErrorCodes::CannotSplit,
              "Unable to find median in chunk because chunk is indivisible.");
}

class SplitCollectionCmd : public ErrmsgCommandDeprecated {
public:
    SplitCollectionCmd() : ErrmsgCommandDeprecated("split") {}

    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }

    bool adminOnly() const override {
        return true;
    }

    bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }

    std::string help() const override {
        return " example: - split the shard that contains give key\n"
               "   { split : 'alleyinsider.blog.posts' , find : { ts : 1 } }\n"
               " example: - split the shard that contains the key with this as the middle\n"
               "   { split : 'alleyinsider.blog.posts' , middle : { ts : 1 } }\n"
               " NOTE: this does not move the chunks, it just creates a logical separation.";
    }

    Status checkAuthForCommand(Client* client,
                               const std::string& dbname,
                               const BSONObj& cmdObj) const override {
        if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
                ResourcePattern::forExactNamespace(NamespaceString(parseNs(dbname, cmdObj))),
                ActionType::splitChunk)) {
            return Status(ErrorCodes::Unauthorized, "Unauthorized");
        }
        return Status::OK();
    }

    std::string parseNs(const std::string& dbname, const BSONObj& cmdObj) const override {
        return CommandHelpers::parseNsFullyQualified(cmdObj);
    }

    bool errmsgRun(OperationContext* opCtx,
                   const std::string& dbname,
                   const BSONObj& cmdObj,
                   std::string& errmsg,
                   BSONObjBuilder& result) override {
        const NamespaceString nss(parseNs(dbname, cmdObj));

        const auto cm = uassertStatusOK(
            Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx,
                                                                                         nss));

        const BSONField<BSONObj> findField("find", BSONObj());
        const BSONField<BSONArray> boundsField("bounds", BSONArray());
        const BSONField<BSONObj> middleField("middle", BSONObj());

        BSONObj find;
        if (FieldParser::extract(cmdObj, findField, &find, &errmsg) == FieldParser::FIELD_INVALID) {
            return false;
        }

        BSONArray bounds;
        if (FieldParser::extract(cmdObj, boundsField, &bounds, &errmsg) ==
            FieldParser::FIELD_INVALID) {
            return false;
        }

        if (!bounds.isEmpty()) {
            if (!bounds.hasField("0")) {
                errmsg = "lower bound not specified";
                return false;
            }

            if (!bounds.hasField("1")) {
                errmsg = "upper bound not specified";
                return false;
            }
        }

        if (!find.isEmpty() && !bounds.isEmpty()) {
            errmsg = "cannot specify bounds and find at the same time";
            return false;
        }

        BSONObj middle;

        if (FieldParser::extract(cmdObj, middleField, &middle, &errmsg) ==
            FieldParser::FIELD_INVALID) {
            return false;
        }

        if (find.isEmpty() && bounds.isEmpty() && middle.isEmpty()) {
            errmsg = "need to specify find/bounds or middle";
            return false;
        }

        if (!find.isEmpty() && !middle.isEmpty()) {
            errmsg = "cannot specify find and middle together";
            return false;
        }

        if (!bounds.isEmpty() && !middle.isEmpty()) {
            errmsg = "cannot specify bounds and middle together";
            return false;
        }

        boost::optional<Chunk> chunk;

        if (!find.isEmpty()) {
            // find
            BSONObj shardKey =
                uassertStatusOK(cm.getShardKeyPattern().extractShardKeyFromQuery(opCtx, nss, find));
            if (shardKey.isEmpty()) {
                errmsg = str::stream() << "no shard key found in chunk query " << find;
                return false;
            }

            chunk.emplace(cm.findIntersectingChunkWithSimpleCollation(shardKey));
        } else if (!bounds.isEmpty()) {
            // bounds
            if (!cm.getShardKeyPattern().isShardKey(bounds[0].Obj()) ||
                !cm.getShardKeyPattern().isShardKey(bounds[1].Obj())) {
                errmsg = str::stream()
                    << "shard key bounds "
                    << "[" << bounds[0].Obj() << "," << bounds[1].Obj() << ")"
                    << " are not valid for shard key pattern " << cm.getShardKeyPattern().toBSON();
                return false;
            }

            BSONObj minKey = cm.getShardKeyPattern().normalizeShardKey(bounds[0].Obj());
            BSONObj maxKey = cm.getShardKeyPattern().normalizeShardKey(bounds[1].Obj());

            chunk.emplace(cm.findIntersectingChunkWithSimpleCollation(minKey));

            if (chunk->getMin().woCompare(minKey) != 0 || chunk->getMax().woCompare(maxKey) != 0) {
                errmsg = str::stream() << "no chunk found with the shard key bounds "
                                       << ChunkRange(minKey, maxKey).toString();
                return false;
            }
        } else {
            // middle
            if (!cm.getShardKeyPattern().isShardKey(middle)) {
                errmsg = str::stream()
                    << "new split key " << middle << " is not valid for shard key pattern "
                    << cm.getShardKeyPattern().toBSON();
                return false;
            }

            middle = cm.getShardKeyPattern().normalizeShardKey(middle);
            chunk.emplace(cm.findIntersectingChunkWithSimpleCollation(middle));

            if (chunk->getMin().woCompare(middle) == 0 || chunk->getMax().woCompare(middle) == 0) {
                errmsg = str::stream()
                    << "new split key " << middle << " is a boundary key of existing chunk "
                    << "[" << chunk->getMin() << "," << chunk->getMax() << ")";
                return false;
            }
        }

        // Once the chunk to be split has been determined, if the split point was explicitly
        // specified in the split command through the "middle" parameter, choose "middle" as the
        // splitPoint. Otherwise use the splitVector command with 'force' to ask the shard for the
        // middle of the chunk.
        const BSONObj splitPoint = !middle.isEmpty()
            ? middle
            : selectMedianKey(opCtx,
                              chunk->getShardId(),
                              nss,
                              cm.getShardKeyPattern(),
                              cm.getVersion(chunk->getShardId()),
                              ChunkRange(chunk->getMin(), chunk->getMax()));

        LOGV2(22758,
              "Splitting chunk {chunkRange} in {namespace} on shard {shardId} at key {splitPoint}",
              "Splitting chunk",
              "chunkRange"_attr = redact(ChunkRange(chunk->getMin(), chunk->getMax()).toString()),
              "splitPoint"_attr = redact(splitPoint),
              "namespace"_attr = nss.ns(),
              "shardId"_attr = chunk->getShardId());

        uassertStatusOK(shardutil::splitChunkAtMultiplePoints(
            opCtx,
            chunk->getShardId(),
            nss,
            cm.getShardKeyPattern(),
            cm.getVersion().epoch(),
            cm.getVersion().getTimestamp(),
            cm.getVersion(chunk->getShardId()) /* shardVersion */,
            ChunkRange(chunk->getMin(), chunk->getMax()),
            {splitPoint}));

        Grid::get(opCtx)
            ->catalogCache()
            ->invalidateShardOrEntireCollectionEntryForShardedCollection(
                nss, boost::none, chunk->getShardId());

        return true;
    }

} splitChunk;

}  // namespace
}  // namespace mongo