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
|
/**
* 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 <vector>
#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/s/catalog/type_chunk.h"
#include "mongo/s/catalog/type_tags.h"
#include "mongo/s/shard_id.h"
#include "mongo/s/shard_key_pattern.h"
namespace mongo {
class InitialSplitPolicy {
public:
/**
* For new collections which use hashed shard keys, we can can pre-split the range of possible
* hashes into a large number of chunks, and distribute them evenly at creation time.
*
* Until we design a better initialization scheme, the most performant way to pre-split is to
* make one big chunk for each shard and migrate them one at a time. Because of this:
* - 'initialSplitPoints' is populated with the split points to use on the primary shard to
* produce the initial "big chunks."
* - 'finalSplitPoints' is populated with the additional split points to use on the "big chunks"
* after the "big chunks" have been spread evenly across shards through migrations.
*/
static void calculateHashedSplitPointsForEmptyCollection(
const ShardKeyPattern& shardKeyPattern,
bool isEmpty,
int numShards,
int numInitialChunks,
std::vector<BSONObj>* initialSplitPoints,
std::vector<BSONObj>* finalSplitPoints);
struct ShardCollectionConfig {
std::vector<ChunkType> chunks;
const auto& collVersion() const {
return chunks.back().getVersion();
}
};
/**
* Produces the initial chunks that need to be written for a collection which is being
* newly-sharded. The function performs some basic validation of the input parameters, but there
* is no checking whether the collection contains any data or not.
*
* Chunks are assigned to a shard in a round-robin fashion, numContiguousChunksPerShard (k)
* chunks at a time. For example, the first k chunks are assigned to the first available shard,
* and the next k chunks are assigned to the second available shard and so on.
* numContiguousChunksPerShard should only be > 1 when we do not pre-split the range
* into larger chunks and then split the resulting chunks on the destination shards as in
* configSvrShardCollection, thus should be equal the number of final split points + 1 divided
* by the number of initial split points + 1. It serves to preserve the ordering/contigousness
* of chunks when split by shardSvrShardCollection so that its yields the exact same shard
* assignments as configSvrShardCollection.
*/
static ShardCollectionConfig generateShardCollectionInitialChunks(
const NamespaceString& nss,
const ShardKeyPattern& shardKeyPattern,
const ShardId& databasePrimaryShardId,
const Timestamp& validAfter,
const std::vector<BSONObj>& splitPoints,
const std::vector<ShardId>& allShardIds,
const int numContiguousChunksPerShard = 1);
/**
* Produces the initial chunks that need to be written for a collection which is being
* newly-sharded based on the given tags. Chunks that do not correspond to any pre-defined
* zones are assigned to available shards in a round-robin fashion.
*/
static ShardCollectionConfig generateShardCollectionInitialZonedChunks(
const NamespaceString& nss,
const ShardKeyPattern& shardKeyPattern,
const Timestamp& validAfter,
const std::vector<TagsType>& tags,
const StringMap<std::vector<ShardId>>& tagToShards,
const std::vector<ShardId>& allShardIds,
const bool isEmpty);
/**
* Creates the first chunks for a newly sharded collection.
* Returns the created chunks.
*/
static ShardCollectionConfig createFirstChunks(OperationContext* opCtx,
const NamespaceString& nss,
const ShardKeyPattern& shardKeyPattern,
const ShardId& primaryShardId,
const std::vector<BSONObj>& splitPoints,
const std::vector<TagsType>& tags,
const bool distributeInitialChunks,
const bool isEmpty,
const int numContiguousChunksPerShard = 1);
/**
* Writes to the config server the first chunks for a newly sharded collection.
*/
static void writeFirstChunksToConfig(
OperationContext* opCtx, const InitialSplitPolicy::ShardCollectionConfig& initialChunks);
};
} // namespace mongo
|
