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/**
* Copyright (C) 2013 MongoDB 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.
*/
#pragma once
#include <string>
#include "mongo/bson/bsonobj.h"
#include "mongo/base/status.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/namespace_string.h"
#include "mongo/s/chunk_version.h"
#include "mongo/s/write_ops/batched_update_document.h"
#include "mongo/s/write_ops/batched_delete_document.h"
namespace mongo {
class OperationContext;
struct ShardEndpoint;
/**
* 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 Status targetInsert(OperationContext* txn,
const BSONObj& doc,
ShardEndpoint** endpoint) 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 Status targetUpdate(OperationContext* txn,
const BatchedUpdateDocument& updateDoc,
std::vector<ShardEndpoint*>* endpoints) 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 Status targetDelete(OperationContext* txn,
const BatchedDeleteDocument& deleteDoc,
std::vector<ShardEndpoint*>* endpoints) const = 0;
/**
* Returns a vector of ShardEndpoints for the entire collection.
*
* Returns !OK with message if the full collection could not be targeted.
*/
virtual Status targetCollection(std::vector<ShardEndpoint*>* endpoints) const = 0;
/**
* Returns a vector of ShardEndpoints for all shards.
*
* Returns !OK with message if all shards could not be targeted.
*/
virtual Status targetAllShards(std::vector<ShardEndpoint*>* endpoints) 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 BSONObj& 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* txn, bool* wasChanged) = 0;
};
/**
* A ShardEndpoint represents a destination for a targeted query or document. It contains both
* the logical target (shard name/version/broadcast) and the physical target (host name).
*/
struct ShardEndpoint {
ShardEndpoint(const ShardEndpoint& other)
: shardName(other.shardName), shardVersion(other.shardVersion) {}
ShardEndpoint(const std::string& shardName, const ChunkVersion& shardVersion)
: shardName(shardName), shardVersion(shardVersion) {}
const std::string shardName;
const ChunkVersion shardVersion;
};
} // namespace mongo
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