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
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
|
/**
* 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.
*/
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding
#include "mongo/platform/basic.h"
#include "mongo/db/s/split_chunk.h"
#include "mongo/base/status_with.h"
#include "mongo/bson/util/bson_extract.h"
#include "mongo/db/catalog/index_catalog.h"
#include "mongo/db/catalog_raii.h"
#include "mongo/db/commands.h"
#include "mongo/db/dbhelpers.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/keypattern.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/query/internal_plans.h"
#include "mongo/db/s/collection_sharding_runtime.h"
#include "mongo/db/s/shard_filtering_metadata_refresh.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/logv2/log.h"
#include "mongo/s/catalog/type_chunk.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/grid.h"
#include "mongo/s/request_types/split_chunk_request_type.h"
namespace mongo {
namespace {
const ReadPreferenceSetting kPrimaryOnlyReadPreference{ReadPreference::PrimaryOnly};
bool checkIfSingleDoc(OperationContext* opCtx,
Collection* collection,
const IndexDescriptor* idx,
const ChunkType* chunk) {
KeyPattern kp(idx->keyPattern());
BSONObj newmin = Helpers::toKeyFormat(kp.extendRangeBound(chunk->getMin(), false));
BSONObj newmax = Helpers::toKeyFormat(kp.extendRangeBound(chunk->getMax(), true));
auto exec = InternalPlanner::indexScan(opCtx,
collection,
idx,
newmin,
newmax,
BoundInclusion::kIncludeStartKeyOnly,
PlanExecutor::NO_YIELD);
// check if exactly one document found
PlanExecutor::ExecState state;
BSONObj obj;
if (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, nullptr))) {
if (PlanExecutor::IS_EOF == (state = exec->getNext(&obj, nullptr))) {
return true;
}
}
// Non-yielding collection scans from InternalPlanner will never error.
invariant(PlanExecutor::ADVANCED == state || PlanExecutor::IS_EOF == state);
return false;
}
/**
* Checks the collection's metadata for a successful split on the specified chunkRange using the
* specified splitKeys. Returns false if the metadata's chunks don't match the new chunk
* boundaries exactly.
*/
bool checkMetadataForSuccessfulSplitChunk(OperationContext* opCtx,
const NamespaceString& nss,
const OID& epoch,
const ChunkRange& chunkRange,
const std::vector<BSONObj>& splitKeys) {
AutoGetCollection autoColl(opCtx, nss, MODE_IS);
const auto metadataAfterSplit =
CollectionShardingRuntime::get(opCtx, nss)->getCurrentMetadataIfKnown();
uassert(ErrorCodes::StaleEpoch,
str::stream() << "Collection " << nss.ns() << " changed since split start",
metadataAfterSplit && metadataAfterSplit->getShardVersion().epoch() == epoch);
auto newChunkBounds(splitKeys);
auto startKey = chunkRange.getMin();
newChunkBounds.push_back(chunkRange.getMax());
ChunkType nextChunk;
for (const auto& endKey : newChunkBounds) {
// Check that all new chunks fit the new chunk boundaries
if (!metadataAfterSplit->getNextChunk(startKey, &nextChunk) ||
nextChunk.getMax().woCompare(endKey)) {
return false;
}
startKey = endKey;
}
return true;
}
} // namespace
StatusWith<boost::optional<ChunkRange>> splitChunk(OperationContext* opCtx,
const NamespaceString& nss,
const BSONObj& keyPatternObj,
const ChunkRange& chunkRange,
const std::vector<BSONObj>& splitKeys,
const std::string& shardName,
const OID& expectedCollectionEpoch) {
const std::string whyMessage(str::stream() << "splitting chunk " << chunkRange.toString()
<< " in " << nss.toString());
auto scopedDistLock = Grid::get(opCtx)->catalogClient()->getDistLockManager()->lock(
opCtx, nss.ns(), whyMessage, DistLockManager::kDefaultLockTimeout);
if (!scopedDistLock.isOK()) {
return scopedDistLock.getStatus().withContext(
str::stream() << "could not acquire collection lock for " << nss.toString()
<< " to split chunk " << chunkRange.toString());
}
// If the shard key is hashed, then we must make sure that the split points are of supported
// data types.
const auto hashedField = ShardKeyPattern::extractHashedField(keyPatternObj);
if (hashedField) {
for (BSONObj splitKey : splitKeys) {
auto hashedSplitElement = splitKey[hashedField.fieldName()];
if (!ShardKeyPattern::isValidHashedValue(hashedSplitElement)) {
return {ErrorCodes::CannotSplit,
str::stream() << "splitChunk cannot split chunk " << chunkRange.toString()
<< ", split point " << hashedSplitElement.toString()
<< "Value of type '" << hashedSplitElement.type()
<< "' is not allowed for hashed fields"};
}
}
}
// Commit the split to the config server.
auto request =
SplitChunkRequest(nss, shardName, expectedCollectionEpoch, chunkRange, splitKeys);
auto configCmdObj =
request.toConfigCommandBSON(ShardingCatalogClient::kMajorityWriteConcern.toBSON());
auto cmdResponseStatus =
Grid::get(opCtx)->shardRegistry()->getConfigShard()->runCommandWithFixedRetryAttempts(
opCtx,
kPrimaryOnlyReadPreference,
"admin",
configCmdObj,
Shard::RetryPolicy::kIdempotent);
// If we failed to get any response from the config server at all, despite retries, then we
// should just go ahead and fail the whole operation.
if (!cmdResponseStatus.isOK()) {
return cmdResponseStatus.getStatus();
}
// Check commandStatus and writeConcernStatus
auto commandStatus = cmdResponseStatus.getValue().commandStatus;
auto writeConcernStatus = cmdResponseStatus.getValue().writeConcernStatus;
// Send stale epoch if epoch of request did not match epoch of collection
if (commandStatus == ErrorCodes::StaleEpoch) {
return commandStatus;
}
//
// If _configsvrCommitChunkSplit returned an error, refresh and look at the metadata to
// determine if the split actually did happen. This can happen if there's a network error
// getting the response from the first call to _configsvrCommitChunkSplit, but it actually
// succeeds, thus the automatic retry fails with a precondition violation, for example.
//
if (!commandStatus.isOK() || !writeConcernStatus.isOK()) {
forceShardFilteringMetadataRefresh(opCtx, nss);
if (checkMetadataForSuccessfulSplitChunk(
opCtx, nss, expectedCollectionEpoch, chunkRange, splitKeys)) {
// Split was committed.
} else if (!commandStatus.isOK()) {
return commandStatus;
} else if (!writeConcernStatus.isOK()) {
return writeConcernStatus;
}
}
AutoGetCollection autoColl(opCtx, nss, MODE_IS);
Collection* const collection = autoColl.getCollection();
if (!collection) {
LOGV2_WARNING(
23778,
"will not perform top-chunk checking since {nss} does not exist after splitting",
"nss"_attr = nss.toString());
return boost::optional<ChunkRange>(boost::none);
}
// Allow multiKey based on the invariant that shard keys must be single-valued. Therefore,
// any multi-key index prefixed by shard key cannot be multikey over the shard key fields.
const IndexDescriptor* idx =
collection->getIndexCatalog()->findShardKeyPrefixedIndex(opCtx, keyPatternObj, false);
if (!idx) {
return boost::optional<ChunkRange>(boost::none);
}
auto backChunk = ChunkType();
backChunk.setMin(splitKeys.back());
backChunk.setMax(chunkRange.getMax());
auto frontChunk = ChunkType();
frontChunk.setMin(chunkRange.getMin());
frontChunk.setMax(splitKeys.front());
KeyPattern shardKeyPattern(keyPatternObj);
if (shardKeyPattern.globalMax().woCompare(backChunk.getMax()) == 0 &&
checkIfSingleDoc(opCtx, collection, idx, &backChunk)) {
return boost::optional<ChunkRange>(ChunkRange(backChunk.getMin(), backChunk.getMax()));
} else if (shardKeyPattern.globalMin().woCompare(frontChunk.getMin()) == 0 &&
checkIfSingleDoc(opCtx, collection, idx, &frontChunk)) {
return boost::optional<ChunkRange>(ChunkRange(frontChunk.getMin(), frontChunk.getMax()));
}
return boost::optional<ChunkRange>(boost::none);
}
} // namespace mongo
|
