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
|
/**
* 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 "mongo/db/range_arithmetic.h"
#include "mongo/s/chunk_manager.h"
namespace mongo {
/**
* The collection metadata has metadata information about a collection, in particular the
* sharding information. It's main goal in life is to be capable of answering if a certain
* document belongs to it or not. (In some scenarios such as chunk migration, a given
* document is in a shard but cannot be accessed.)
*
* To build a collection from config data, please check the MetadataLoader. The methods
* here allow building a new incarnation of a collection's metadata based on an existing
* one (e.g, we're splitting in a given collection.).
*
* This class's chunk mapping is immutable once constructed.
*/
class CollectionMetadata {
public:
/**
* Instantiates a metadata object, which represents an unsharded collection. This 'isSharded'
* for this object will return false and it is illegal to use it for filtering.
*/
CollectionMetadata() = default;
/**
* The main way to construct CollectionMetadata is through MetadataLoader or clone() methods.
*
* "thisShardId" is the shard identity of this shard for purposes of answering questions like
* "does this key belong to this shard"?
*/
CollectionMetadata(std::shared_ptr<ChunkManager> cm, const ShardId& thisShardId);
/**
* Returns whether this metadata object represents a sharded or unsharded collection.
*/
bool isSharded() const {
return bool(_cm);
}
/**
* Returns the current shard version for the collection or UNSHARDED if it is not sharded.
*/
ChunkVersion getShardVersion() const {
return (isSharded() ? _cm->getVersion(_thisShardId) : ChunkVersion::UNSHARDED());
}
/**
* Returns the current collection version or UNSHARDED if it is not sharded.
*/
ChunkVersion getCollVersion() const {
return (isSharded() ? _cm->getVersion() : ChunkVersion::UNSHARDED());
}
/**
* Obtains the shard id with which this collection metadata is configured.
*/
const ShardId& shardId() const {
invariant(isSharded());
return _thisShardId;
}
/**
* Returns true if 'key' contains exactly the same fields as the shard key pattern.
*/
bool isValidKey(const BSONObj& key) const {
invariant(isSharded());
return _cm->getShardKeyPattern().isShardKey(key);
}
const BSONObj& getKeyPattern() const {
invariant(isSharded());
return _cm->getShardKeyPattern().toBSON();
}
const std::vector<std::unique_ptr<FieldRef>>& getKeyPatternFields() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPatternFields();
}
BSONObj getMinKey() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPattern().globalMin();
}
BSONObj getMaxKey() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPattern().globalMax();
}
bool uuidMatches(UUID uuid) const {
invariant(isSharded());
return _cm->uuidMatches(uuid);
}
/**
* Returns just the shard key fields, if the collection is sharded, and the _id field, from
* `doc`. Does not alter any field values (e.g. by hashing); values are copied verbatim.
*/
BSONObj extractDocumentKey(const BSONObj& doc) const;
/**
* BSON output of the basic metadata information (chunk and shard version).
*/
void toBSONBasic(BSONObjBuilder& bb) const;
/**
* String output of the collection and shard versions.
*/
std::string toStringBasic() const;
//
// Methods used for orphan filtering and general introspection of the chunks owned by the shard
//
ChunkManager* getChunkManager() const {
invariant(isSharded());
return _cm.get();
}
/**
* Returns true if the document with the given key belongs to this chunkset. If the key is empty
* returns false. If key is not a valid shard key, the behaviour is undefined.
*/
bool keyBelongsToMe(const BSONObj& key) const {
invariant(isSharded());
return _cm->keyBelongsToShard(key, _thisShardId);
}
/**
* Given a key 'lookupKey' in the shard key range, get the next chunk which overlaps or is
* greater than this key. Returns true if a chunk exists, false otherwise.
*
* Passing a key that is not a valid shard key for this range results in undefined behavior.
*/
bool getNextChunk(const BSONObj& lookupKey, ChunkType* chunk) const;
/**
* Validates that the passed-in chunk's bounds exactly match a chunk in the metadata cache.
*/
Status checkChunkIsValid(const ChunkType& chunk) const;
/**
* Returns true if the argument range overlaps any chunk.
*/
bool rangeOverlapsChunk(const ChunkRange& range) const {
invariant(isSharded());
return _cm->rangeOverlapsShard(range, _thisShardId);
}
/**
* Given a key in the shard key range, get the next range which overlaps or is greater than
* this key.
*
* This allows us to do the following to iterate over all orphan ranges:
*
* ChunkRange range;
* BSONObj lookupKey = metadata->getMinKey();
* boost::optional<ChunkRange> range;
* while((range = metadata->getNextOrphanRange(receiveMap, lookupKey))) {
* lookupKey = range->maxKey;
* }
*
* @param lookupKey passing a key that does not belong to this metadata is undefined.
* @param receiveMap is an extra set of chunks not considered orphaned.
*
* @return orphanRange the output range. Note that the NS is not set.
*/
boost::optional<ChunkRange> getNextOrphanRange(const RangeMap& receiveMap,
const BSONObj& lookupKey) const;
/**
* Returns all the chunks which are contained on this shard.
*/
RangeMap getChunks() const;
/**
* BSON output of the chunks metadata into a BSONArray
*/
void toBSONChunks(BSONArrayBuilder* builder) const;
private:
// The full routing table for the collection or nullptr if the collection is not sharded
std::shared_ptr<ChunkManager> _cm;
// The identity of this shard, for the purpose of answering "key belongs to me" queries. If the
// collection is not sharded (_cm is nullptr), then this value will be empty.
ShardId _thisShardId;
};
} // namespace mongo
|
