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// extent_manager.h
/**
* Copyright (C) 2013 10gen 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 <memory>
#include <string>
#include <vector>
#include "mongo/base/status.h"
#include "mongo/base/string_data.h"
#include "mongo/db/storage/mmap_v1/diskloc.h"
namespace mongo {
class DataFile;
class DataFileVersion;
class MmapV1RecordHeader;
class RecordFetcher;
class OperationContext;
struct Extent;
/**
* ExtentManager basics
* - one per database
* - responsible for managing <db>.# files
* - NOT responsible for .ns file
* - gives out extents
* - responsible for figuring out how to get a new extent
* - can use any method it wants to do so
* - this structure is NOT stored on disk
* - files will not be removed from the EM
* - extent size and loc are immutable
* - this class is thread safe, once constructed and init()-ialized
*/
class ExtentManager {
MONGO_DISALLOW_COPYING(ExtentManager);
public:
ExtentManager() {}
class Factory {
public:
virtual ~Factory() = default;
virtual std::unique_ptr<ExtentManager> create(StringData dbname,
StringData path,
bool directoryPerDB) = 0;
};
virtual ~ExtentManager() {}
virtual void close(OperationContext* txn) = 0;
/**
* opens all current files
*/
virtual Status init(OperationContext* txn) = 0;
virtual int numFiles() const = 0;
virtual long long fileSize() const = 0;
// must call Extent::reuse on the returned extent
virtual DiskLoc allocateExtent(OperationContext* txn,
bool capped,
int size,
bool enforceQuota) = 0;
/**
* firstExt has to be == lastExt or a chain
*/
virtual void freeExtents(OperationContext* txn, DiskLoc firstExt, DiskLoc lastExt) = 0;
/**
* frees a single extent
* ignores all fields in the Extent except: magic, myLoc, length
*/
virtual void freeExtent(OperationContext* txn, DiskLoc extent) = 0;
/**
* Retrieve statistics on the the free list managed by this ExtentManger.
* @param numExtents - non-null pointer to an int that will receive the number of extents
* @param totalFreeSizeBytes - non-null pointer to an int64_t receiving the total free
* space in the free list.
*/
virtual void freeListStats(OperationContext* txn,
int* numExtents,
int64_t* totalFreeSizeBytes) const = 0;
/**
* @param loc - has to be for a specific MmapV1RecordHeader
* Note(erh): this sadly cannot be removed.
* A MmapV1RecordHeader DiskLoc has an offset from a file, while a RecordStore really wants an
* offset from an extent. This intrinsically links an original record store to the original
* extent manager.
*/
virtual MmapV1RecordHeader* recordForV1(const DiskLoc& loc) const = 0;
/**
* The extent manager tracks accesses to DiskLocs. This returns non-NULL if the DiskLoc has
* been recently accessed, and therefore has likely been paged into physical memory.
* Returns nullptr if the DiskLoc is Null.
*
*/
virtual std::unique_ptr<RecordFetcher> recordNeedsFetch(const DiskLoc& loc) const = 0;
/**
* @param loc - has to be for a specific MmapV1RecordHeader (not an Extent)
* Note(erh) see comment on recordFor
*/
virtual Extent* extentForV1(const DiskLoc& loc) const = 0;
/**
* @param loc - has to be for a specific MmapV1RecordHeader (not an Extent)
* Note(erh) see comment on recordFor
*/
virtual DiskLoc extentLocForV1(const DiskLoc& loc) const = 0;
/**
* @param loc - has to be for a specific Extent
*/
virtual Extent* getExtent(const DiskLoc& loc, bool doSanityCheck = true) const = 0;
/**
* @return maximum size of an Extent
*/
virtual int maxSize() const = 0;
/**
* @return minimum size of an Extent
*/
virtual int minSize() const {
return 0x1000;
}
/**
* @param recordLen length of record we need
* @param lastExt size of last extent which is a factor in next extent size
*/
virtual int followupSize(int recordLen, int lastExtentLen) const;
/** get a suggested size for the first extent in a namespace
* @param recordLen length of record we need to insert
*/
virtual int initialSize(int recordLen) const;
/**
* quantizes extent size to >= min + page boundary
*/
virtual int quantizeExtentSize(int size) const;
// see cacheHint methods
enum HintType { Sequential, Random };
class CacheHint {
public:
virtual ~CacheHint() {}
};
/**
* Tell the system that for this extent, it will have this kind of disk access.
* Caller takes owernship of CacheHint
*/
virtual CacheHint* cacheHint(const DiskLoc& extentLoc, const HintType& hint) = 0;
virtual DataFileVersion getFileFormat(OperationContext* txn) const = 0;
virtual void setFileFormat(OperationContext* txn, DataFileVersion newVersion) = 0;
virtual const DataFile* getOpenFile(int n) const = 0;
};
} // namespace mongo
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