1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
/**
* 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 <boost/optional.hpp>
#include "mongo/s/catalog/type_chunk.h"
#include "mongo/s/chunk_version.h"
#include "mongo/s/client/shard.h"
namespace mongo {
class ChunkManager;
class ChunkType;
class OperationContext;
/**
config.chunks
{ ns : "alleyinsider.fs.chunks" , min : {} , max : {} , server : "localhost:30001" }
x is in a shard iff
min <= x < max
*/
class Chunk {
MONGO_DISALLOW_COPYING(Chunk);
public:
enum SplitPointMode {
// Determines the split points that will make the current chunk smaller than
// the current chunk size setting. Gives empty result if chunk is not big enough.
normal,
// Will get a split which approximately splits the chunk into 2 halves,
// regardless of the size of the chunk.
atMedian,
// Behaves like normal, with additional special heuristics for "top chunks"
// (the 1 or 2 chunks in the extreme ends of the chunk key space).
autoSplitInternal
};
Chunk(OperationContext* txn, ChunkManager* manager, const ChunkType& from);
Chunk(ChunkManager* manager,
const BSONObj& min,
const BSONObj& max,
const ShardId& shardId,
ChunkVersion lastmod,
uint64_t initialDataWritten);
//
// chunk boundary support
//
const BSONObj& getMin() const {
return _min;
}
const BSONObj& getMax() const {
return _max;
}
// Returns true if this chunk contains the given shard key, and false otherwise
//
// Note: this function takes an extracted *key*, not an original document
// (the point may be computed by, say, hashing a given field or projecting
// to a subset of fields).
bool containsKey(const BSONObj& shardKey) const;
//
// chunk version support
//
void appendShortVersion(const char* name, BSONObjBuilder& b) const;
ChunkVersion getLastmod() const {
return _lastmod;
}
//
// split support
//
long long getBytesWritten() const {
return _dataWritten;
}
/**
* if the amount of data written nears the max size of a shard
* then we check the real size, and if its too big, we split
* @return if something was split
*/
bool splitIfShould(OperationContext* txn, long dataWritten);
/**
* Splits this chunk at a non-specificed split key to be chosen by the
* mongod holding this chunk.
*
* @param mode
* @param res the object containing details about the split execution
* @param resultingSplits the number of resulting split points. Set to NULL to ignore.
*
* @throws UserException
*/
StatusWith<boost::optional<ChunkRange>> split(OperationContext* txn,
SplitPointMode mode,
size_t* resultingSplits) const;
/**
* marks this chunk as a jumbo chunk
* that means the chunk will be inelligble for migrates
*/
void markAsJumbo(OperationContext* txn) const;
bool isJumbo() const {
return _jumbo;
}
//
// public constants
//
static const int MaxObjectPerChunk{250000};
//
// accessors and helpers
//
std::string toString() const;
friend std::ostream& operator<<(std::ostream& out, const Chunk& c) {
return (out << c.toString());
}
// chunk equality is determined by comparing the min and max bounds of the chunk
bool operator==(const Chunk& s) const;
bool operator!=(const Chunk& s) const {
return !(*this == s);
}
ShardId getShardId() const {
return _shardId;
}
const ChunkManager* getManager() const {
return _manager;
}
private:
/**
* Returns the connection string for the shard on which this chunk resides.
*/
ConnectionString _getShardConnectionString(OperationContext* txn) const;
// if min/max key is pos/neg infinity
bool _minIsInf() const;
bool _maxIsInf() const;
// The chunk manager, which owns this chunk. Not owned by the chunk.
const ChunkManager* _manager;
BSONObj _min;
BSONObj _max;
ShardId _shardId;
const ChunkVersion _lastmod;
mutable bool _jumbo;
// Statistics for the approximate data written by this chunk
uint64_t _dataWritten;
// methods, etc..
/**
* Returns the split point that will result in one of the chunk having exactly one
* document. Also returns an empty document if the split point cannot be determined.
*
* @param doSplitAtLower determines which side of the split will have exactly one document.
* True means that the split point chosen will be closer to the lower bound.
*
* Warning: this assumes that the shard key is not "special"- that is, the shardKeyPattern
* is simply an ordered list of ascending/descending field names. Examples:
* {a : 1, b : -1} is not special. {a : "hashed"} is.
*/
BSONObj _getExtremeKey(OperationContext* txn, bool doSplitAtLower) const;
/**
* Determines the appropriate split points for this chunk.
*
* @param atMedian perform a single split at the middle of this chunk.
* @param splitPoints out parameter containing the chosen split points. Can be empty.
*/
std::vector<BSONObj> _determineSplitPoints(OperationContext* txn, bool atMedian) const;
/**
* initializes _dataWritten with a random value so that a mongos restart
* wouldn't cause delay in splitting
*/
static int mkDataWritten();
};
} // namespace mongo
|
