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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.
*/
#pragma once
#include <atomic>
#include "mongo/client/connection_string.h"
#include "mongo/db/query/explain_options.h"
#include "mongo/s/client/shard.h"
namespace mongo {
class DbMessage;
struct DbResponse;
class Message;
class NamespaceString;
class OperationContext;
class QueryRequest;
/**
* Legacy interface for processing client read/write/cmd requests.
*/
class Strategy {
public:
/**
* Handles a legacy-style opQuery request and sends the response back on success or throws on
* error.
*
* Must not be called with legacy '.$cmd' commands.
*/
static DbResponse queryOp(OperationContext* opCtx, const NamespaceString& nss, DbMessage* dbm);
/**
* Handles a legacy-style getMore request and sends the response back on success (or cursor not
* found) or throws on error.
*/
static DbResponse getMore(OperationContext* opCtx, const NamespaceString& nss, DbMessage* dbm);
/**
* Handles a legacy-style killCursors request. Doesn't send any response on success or throws on
* error.
*/
static void killCursors(OperationContext* opCtx, DbMessage* dbm);
/**
* Handles a legacy-style write operation request and updates the last error state on the client
* with the result from the operation. Doesn't send any response back and does not throw on
* errors.
*/
static void writeOp(OperationContext* opCtx, DbMessage* dbm);
/**
* Executes a command from either OP_QUERY or OP_MSG wire protocols.
*
* Catches StaleConfigException errors and retries the command automatically after refreshing
* the metadata for the failing namespace.
*/
static DbResponse clientCommand(OperationContext* opCtx, const Message& message);
/**
* Helper to run an explain of a find operation on the shards. Fills 'out' with the result of
* the of the explain command on success. On failure, throws and does not modify 'out'.
*
* Used both if mongos receives an explain command and if it receives an OP_QUERY find with the
* $explain modifier.
*/
static void explainFind(OperationContext* opCtx,
const BSONObj& findCommand,
const QueryRequest& qr,
ExplainOptions::Verbosity verbosity,
const ReadPreferenceSetting& readPref,
BSONObjBuilder* out);
struct CommandResult {
CommandResult() = default;
CommandResult(ShardId shardId, ConnectionString target, BSONObj result)
: shardTargetId(std::move(shardId)),
target(std::move(target)),
result(std::move(result)) {}
ShardId shardTargetId;
ConnectionString target;
BSONObj result;
};
/**
* Executes a command against a particular database, and targets the command based on a
* collection in that database, according to 'targetingQuery' and 'targetingCollation'. If
* 'targetingCollation' is empty, the collection default collation is used for targeting.
*
* This version should be used by internal commands when possible.
*
* TODO: Replace these methods and all other methods of command dispatch with a more general
* command op framework.
*/
static void commandOp(OperationContext* opCtx,
const std::string& db,
const BSONObj& command,
const std::string& versionedNS,
const BSONObj& targetingQuery,
const BSONObj& targetingCollation,
std::vector<CommandResult>* results);
};
} // namespace mongo
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