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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_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding
#include "mongo/platform/basic.h"
#include "mongo/s/config_server_catalog_cache_loader.h"
#include <memory>
#include "mongo/db/client.h"
#include "mongo/db/operation_context.h"
#include "mongo/logv2/log.h"
#include "mongo/s/catalog/sharding_catalog_client.h"
#include "mongo/s/grid.h"
#include "mongo/util/fail_point.h"
namespace mongo {
using CollectionAndChangedChunks = CatalogCacheLoader::CollectionAndChangedChunks;
namespace {
MONGO_FAIL_POINT_DEFINE(hangBeforeReadingChunks);
/**
* Structure repsenting the generated query and sort order for a chunk diffing operation.
*/
struct QueryAndSort {
const BSONObj query;
const BSONObj sort;
};
/**
* Returns the query needed to find incremental changes to a collection from the config server.
*
* The query has to find all the chunks $gte the current max version. Currently, any splits and
* merges will increment the current max version.
*
* The sort needs to be by ascending version in order to pick up the chunks which changed most
* recent and also in order to handle cursor yields between chunks being migrated/split/merged. This
* ensures that changes to chunk version (which will always be higher) will always come *after* our
* current position in the chunk cursor.
*/
QueryAndSort createConfigDiffQueryNs(const NamespaceString& nss, ChunkVersion collectionVersion) {
return {BSON(ChunkType::ns() << nss.ns() << ChunkType::lastmod() << GTE
<< Timestamp(collectionVersion.toLong())),
BSON(ChunkType::lastmod() << 1)};
}
QueryAndSort createConfigDiffQueryUuid(const UUID& uuid, ChunkVersion collectionVersion) {
return {BSON(ChunkType::collectionUUID()
<< uuid << ChunkType::lastmod() << GTE << Timestamp(collectionVersion.toLong())),
BSON(ChunkType::lastmod() << 1)};
}
/**
* Blocking method, which returns the chunks which changed since the specified version.
*/
CollectionAndChangedChunks getChangedChunks(OperationContext* opCtx,
const NamespaceString& nss,
ChunkVersion sinceVersion) {
const auto catalogClient = Grid::get(opCtx)->catalogClient();
// Decide whether to do a full or partial load based on the state of the collection
const auto coll = catalogClient->getCollection(opCtx, nss);
uassert(ErrorCodes::NamespaceNotFound,
str::stream() << "Collection " << nss.ns() << " is dropped.",
!coll.getDropped());
// If the collection's epoch has changed, do a full refresh
const ChunkVersion startingCollectionVersion = (sinceVersion.epoch() == coll.getEpoch())
? sinceVersion
: ChunkVersion(0, 0, coll.getEpoch(), coll.getTimestamp());
// Diff tracker should *always* find at least one chunk if collection exists
const auto diffQuery = [&]() {
if (coll.getTimestamp()) {
return createConfigDiffQueryUuid(coll.getUuid(), startingCollectionVersion);
} else {
return createConfigDiffQueryNs(nss, startingCollectionVersion);
}
}();
if (MONGO_unlikely(hangBeforeReadingChunks.shouldFail())) {
LOGV2(5310504, "Hit hangBeforeReadingChunks failpoint");
hangBeforeReadingChunks.pauseWhileSet(opCtx);
}
// TODO SERVER-53283: Remove once 5.0 has branched out.
// Use a hint to make sure the query will use an index. This ensures that the query on
// config.chunks will only execute if config.chunks is guaranteed to still have the same
// metadata format as we inferred from the config.collections entry we read.
// This is because when the config.chunks are patched up as part of the FCV upgrade (or
// downgrade), first the ns_1_lastmod_1 index (or uuid_1_lastmod_1) is dropped, then the 'ns'
// (or 'uuid') fields are unset from config.chunks. If the query is forced to use the expected
// index, we can guarantee that the config.chunks we will read will have the expected format. If
// it doesn't, it means that it's being patched-up. Then the query will fail and the refresh
// will be retried, this time expecting the new metadata format.
const auto hint = coll.getTimestamp()
? BSON(ChunkType::collectionUUID() << 1 << ChunkType::lastmod() << 1)
: BSON(ChunkType::ns() << 1 << ChunkType::lastmod() << 1);
// Query the chunks which have changed
repl::OpTime opTime;
const std::vector<ChunkType> changedChunks = uassertStatusOK(
Grid::get(opCtx)->catalogClient()->getChunks(opCtx,
diffQuery.query,
diffQuery.sort,
boost::none,
&opTime,
repl::ReadConcernLevel::kMajorityReadConcern,
hint));
uassert(ErrorCodes::ConflictingOperationInProgress,
"No chunks were found for the collection",
!changedChunks.empty());
return CollectionAndChangedChunks{coll.getEpoch(),
coll.getTimestamp(),
coll.getUuid(),
coll.getKeyPattern().toBSON(),
coll.getDefaultCollation(),
coll.getUnique(),
coll.getReshardingFields(),
coll.getAllowMigrations(),
std::move(changedChunks)};
}
} // namespace
ConfigServerCatalogCacheLoader::ConfigServerCatalogCacheLoader()
: _executor(std::make_shared<ThreadPool>([] {
ThreadPool::Options options;
options.poolName = "ConfigServerCatalogCacheLoader";
options.minThreads = 0;
options.maxThreads = 6;
return options;
}())) {
_executor->startup();
}
void ConfigServerCatalogCacheLoader::initializeReplicaSetRole(bool isPrimary) {
MONGO_UNREACHABLE;
}
void ConfigServerCatalogCacheLoader::onStepDown() {
MONGO_UNREACHABLE;
}
void ConfigServerCatalogCacheLoader::onStepUp() {
MONGO_UNREACHABLE;
}
void ConfigServerCatalogCacheLoader::shutDown() {
_executor->shutdown();
_executor->join();
}
void ConfigServerCatalogCacheLoader::notifyOfCollectionVersionUpdate(const NamespaceString& nss) {
MONGO_UNREACHABLE;
}
void ConfigServerCatalogCacheLoader::waitForCollectionFlush(OperationContext* opCtx,
const NamespaceString& nss) {
MONGO_UNREACHABLE;
}
void ConfigServerCatalogCacheLoader::waitForDatabaseFlush(OperationContext* opCtx,
StringData dbName) {
MONGO_UNREACHABLE;
}
SemiFuture<CollectionAndChangedChunks> ConfigServerCatalogCacheLoader::getChunksSince(
const NamespaceString& nss, ChunkVersion version) {
return ExecutorFuture<void>(_executor)
.then([=]() {
ThreadClient tc("ConfigServerCatalogCacheLoader::getChunksSince",
getGlobalServiceContext());
auto opCtx = tc->makeOperationContext();
return getChangedChunks(opCtx.get(), nss, version);
})
.semi();
}
SemiFuture<DatabaseType> ConfigServerCatalogCacheLoader::getDatabase(StringData dbName) {
return ExecutorFuture<void>(_executor)
.then([name = dbName.toString()] {
ThreadClient tc("ConfigServerCatalogCacheLoader::getDatabase",
getGlobalServiceContext());
auto opCtx = tc->makeOperationContext();
return Grid::get(opCtx.get())
->catalogClient()
->getDatabase(opCtx.get(), name, repl::ReadConcernLevel::kMajorityReadConcern);
})
.semi();
}
} // namespace mongo
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