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/**
* 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_LOG_DEFAULT_COMPONENT ::mongo::logger::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_metadata.h"
#include "mongo/db/s/collection_sharding_state.h"
#include "mongo/db/s/shard_filtering_metadata_refresh.h"
#include "mongo/db/s/sharding_state.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"
#include "mongo/util/log.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) {
const auto metadataAfterSplit = [&] {
AutoGetCollection autoColl(opCtx, nss, MODE_IS);
return CollectionShardingState::get(opCtx, nss)->getCurrentMetadata();
}();
uassert(ErrorCodes::StaleEpoch,
str::stream() << "Collection " << nss.ns() << " changed since split start",
metadataAfterSplit->getCollVersion().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) {
//
// TODO(SERVER-25086): Remove distLock acquisition from split chunk
//
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 type
// NumberLong.
if (KeyPattern::isHashedKeyPattern(keyPatternObj)) {
for (BSONObj splitKey : splitKeys) {
BSONObjIterator it(splitKey);
while (it.more()) {
BSONElement splitKeyElement = it.next();
if (splitKeyElement.type() != NumberLong) {
return {ErrorCodes::CannotSplit,
str::stream()
<< "splitChunk cannot split chunk " << chunkRange.toString()
<< ", split point " << splitKeyElement.toString()
<< " must be of type "
"NumberLong for hashed shard key patterns"};
}
}
}
}
// 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) {
warning() << "will not perform top-chunk checking since " << nss.toString()
<< " does not exist after splitting";
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
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