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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 <vector>
#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/ops/write_ops.h"
#include "mongo/s/chunk_version.h"
#include "mongo/s/shard_id.h"
#include "mongo/s/stale_exception.h"
namespace mongo {
class OperationContext;
/**
* Combines a shard and the version which that shard should be using
*/
struct ShardEndpoint {
ShardEndpoint(const ShardId& shardName, const ChunkVersion& shardVersion)
: shardName(shardName), shardVersion(shardVersion) {}
ShardEndpoint(const ShardEndpoint& other)
: shardName(other.shardName), shardVersion(other.shardVersion) {}
ShardId shardName;
ChunkVersion shardVersion;
};
/**
* The NSTargeter interface is used by a WriteOp to generate and target child write operations
* to a particular collection.
*
* The lifecyle of a NSTargeter is:
*
* 0. targetDoc/targetQuery as many times as is required
*
* 1a. On targeting failure we may need to refresh, note that it happened.
* 1b. On stale config from a child write operation we may need to refresh, note the error.
*
* 2. RefreshIfNeeded() to get newer targeting information
*
* 3. Goto 0.
*
* The refreshIfNeeded() operation must try to make progress against noted targeting or stale
* config failures, see comments below. No functions may block for shared resources or network
* calls except refreshIfNeeded().
*
* Implementers are free to define more specific targeting error codes to allow more complex
* error handling.
*
* Interface must be externally synchronized if used in multiple threads, for now.
* TODO: Determine if we should internally synchronize.
*/
class NSTargeter {
public:
virtual ~NSTargeter() {}
/**
* Returns the namespace targeted.
*/
virtual const NamespaceString& getNS() const = 0;
/**
* Returns a ShardEndpoint for a single document write.
*
* Returns !OK with message if document could not be targeted for other reasons.
*/
virtual StatusWith<ShardEndpoint> targetInsert(OperationContext* opCtx,
const BSONObj& doc) const = 0;
/**
* Returns a vector of ShardEndpoints for a potentially multi-shard update.
*
* Returns OK and fills the endpoints; returns a status describing the error otherwise.
*/
virtual StatusWith<std::vector<ShardEndpoint>> targetUpdate(
OperationContext* opCtx, const write_ops::UpdateOpEntry& updateDoc) const = 0;
/**
* Returns a vector of ShardEndpoints for a potentially multi-shard delete.
*
* Returns OK and fills the endpoints; returns a status describing the error otherwise.
*/
virtual StatusWith<std::vector<ShardEndpoint>> targetDelete(
OperationContext* opCtx, const write_ops::DeleteOpEntry& deleteDoc) const = 0;
/**
* Returns a vector of ShardEndpoints for the entire collection.
*
* Returns !OK with message if the full collection could not be targeted.
*/
virtual StatusWith<std::vector<ShardEndpoint>> targetCollection() const = 0;
/**
* Returns a vector of ShardEndpoints for all shards.
*
* Returns !OK with message if all shards could not be targeted.
*/
virtual StatusWith<std::vector<ShardEndpoint>> targetAllShards(
OperationContext* opCtx) const = 0;
/**
* Informs the targeter that a targeting failure occurred during one of the last targeting
* operations. If this is noted, we cannot note stale responses.
*/
virtual void noteCouldNotTarget() = 0;
/**
* Informs the targeter of stale config responses for this namespace from an endpoint, with
* further information available in the returned staleInfo.
*
* Any stale responses noted here will be taken into account on the next refresh.
*
* If stale responses are is noted, we must not have noted that we cannot target.
*/
virtual void noteStaleResponse(const ShardEndpoint& endpoint,
const StaleConfigInfo& staleInfo) = 0;
/**
* Refreshes the targeting metadata for the namespace if needed, based on previously-noted
* stale responses and targeting failures.
*
* After this function is called, the targeter should be in a state such that the noted
* stale responses are not seen again and if a targeting failure occurred it reloaded -
* it should try to make progress. If provided, wasChanged is set to true if the targeting
* information used here was changed.
*
* NOTE: This function may block for shared resources or network calls.
* Returns !OK with message if could not refresh
*/
virtual Status refreshIfNeeded(OperationContext* opCtx, bool* wasChanged) = 0;
};
} // namespace mongo
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