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/**
* Copyright (C) 2008-2015 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/bson/simple_bsonobj_comparator.h"
#include "mongo/s/client/shard.h"
namespace mongo {
class ChunkType;
struct ChunkVersion;
class OperationContext;
class ConfigDiffTrackerBase {
public:
/**
* Structure repsenting the generated query and sort order for a chunk diffing operation.
*/
struct QueryAndSort {
const BSONObj query;
const BSONObj sort;
};
/**
* Returns the query needed to find incremental changes to a collection from the config server.
*/
static QueryAndSort createConfigDiffQuery(const NamespaceString& nss,
ChunkVersion collectionVersion);
};
/**
* This class manages and applies diffs from partial config server data reloads. Because the config
* data can be large, we want to update it in small parts, not all-at-once. Once a
* ConfigDiffTracker is created, the current config data is *attached* to it, and it is then able
* to modify the data.
*
* The current form is templated b/c the overall algorithm is identical between mongos and mongod,
* but the actual chunk maps used differ in implementation. We don't want to copy the
* implementation, because the logic is identical, or the chunk data, because that would be slow
* for big clusters, so this is the alternative for now.
*
* TODO: Standardize between mongos and mongod and convert template parameters to types.
*/
template <class ValType>
class ConfigDiffTracker : public ConfigDiffTrackerBase {
public:
// Stores ranges indexed by max or min key.
typedef BSONObjIndexedMap<ValType> RangeMap;
// Pair of iterators defining a subset of ranges
typedef typename std::pair<typename RangeMap::iterator, typename RangeMap::iterator>
RangeOverlap;
// Map of shard identifiers to the maximum chunk version on that shard
typedef typename std::map<ShardId, ChunkVersion> MaxChunkVersionMap;
/**
* The tracker attaches to a set of ranges with versions, and uses the catalog client to update
* these. Because the set of ranges and versions may be large, they aren't owned by the tracker,
* they're just passed in and updated. Therefore they must all stay in scope while the tracker
* is working.
*/
ConfigDiffTracker(const std::string& ns,
RangeMap* currMap,
ChunkVersion* maxVersion,
MaxChunkVersionMap* maxShardVersions);
virtual ~ConfigDiffTracker();
// Call after load for more information
int numValidDiffs() const {
return _validDiffs;
}
// Applies changes to the config data from a vector of chunks passed in. Also includes minor
// version changes for particular major-version chunks if explicitly specified.
// Returns the number of diffs processed, or -1 if the diffs were inconsistent.
int calculateConfigDiff(OperationContext* txn, const std::vector<ChunkType>& chunks);
protected:
/**
* Determines which chunks are actually being remembered by our RangeMap. Allows individual
* shards to filter out results, which belong to the local shard only.
*/
virtual bool isTracked(const ChunkType& chunk) const = 0;
/**
* Whether or not our RangeMap uses min or max keys
*/
virtual bool isMinKeyIndexed() const {
return true;
}
virtual std::pair<BSONObj, ValType> rangeFor(OperationContext* txn,
const ChunkType& chunk) const = 0;
virtual ShardId shardFor(OperationContext* txn, const ShardId& name) const = 0;
private:
// Whether or not a range exists in the min/max region
bool _isOverlapping(const BSONObj& min, const BSONObj& max);
// Returns a subset of ranges overlapping the region min/max
RangeOverlap _overlappingRange(const BSONObj& min, const BSONObj& max);
const std::string _ns;
RangeMap* const _currMap;
ChunkVersion* const _maxVersion;
MaxChunkVersionMap* const _maxShardVersions;
// Store for later use
int _validDiffs{0};
};
} // namespace mongo
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