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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/balancer/scoped_migration_request.h"
#include "mongo/db/s/balancer/type_migration.h"
#include "mongo/db/write_concern_options.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/grid.h"
#include "mongo/util/log.h"
namespace mongo {
namespace {
const WriteConcernOptions kMajorityWriteConcern(WriteConcernOptions::kMajority,
WriteConcernOptions::SyncMode::UNSET,
WriteConcernOptions::kWriteConcernTimeoutMigration);
const int kDuplicateKeyErrorMaxRetries = 2;
} // namespace
ScopedMigrationRequest::ScopedMigrationRequest(OperationContext* opCtx,
const NamespaceString& nss,
const BSONObj& minKey)
: _opCtx(opCtx), _nss(nss), _minKey(minKey) {}
ScopedMigrationRequest::~ScopedMigrationRequest() {
if (!_opCtx) {
// If the opCtx object was cleared, nothing should happen in the destructor.
return;
}
// Try to delete the entry in the config.migrations collection. If the command fails, that is
// okay.
BSONObj migrationDocumentIdentifier =
BSON(MigrationType::ns(_nss.ns()) << MigrationType::min(_minKey));
Status result = Grid::get(_opCtx)->catalogClient()->removeConfigDocuments(
_opCtx, MigrationType::ConfigNS, migrationDocumentIdentifier, kMajorityWriteConcern);
if (!result.isOK()) {
LOG(0) << "Failed to remove config.migrations document for migration '"
<< migrationDocumentIdentifier.toString() << "'" << causedBy(redact(result));
}
}
ScopedMigrationRequest::ScopedMigrationRequest(ScopedMigrationRequest&& other) {
*this = std::move(other);
// Set opCtx to null so that the destructor will do nothing.
other._opCtx = nullptr;
}
ScopedMigrationRequest& ScopedMigrationRequest::operator=(ScopedMigrationRequest&& other) {
if (this != &other) {
_opCtx = other._opCtx;
_nss = other._nss;
_minKey = other._minKey;
// Set opCtx to null so that the destructor will do nothing.
other._opCtx = nullptr;
}
return *this;
}
StatusWith<ScopedMigrationRequest> ScopedMigrationRequest::writeMigration(
OperationContext* opCtx, const MigrateInfo& migrateInfo, bool waitForDelete) {
auto const grid = Grid::get(opCtx);
// Try to write a unique migration document to config.migrations.
const MigrationType migrationType(migrateInfo, waitForDelete);
for (int retry = 0; retry < kDuplicateKeyErrorMaxRetries; ++retry) {
Status result = grid->catalogClient()->insertConfigDocument(
opCtx, MigrationType::ConfigNS, migrationType.toBSON(), kMajorityWriteConcern);
if (result == ErrorCodes::DuplicateKey) {
// If the exact migration described by "migrateInfo" is active, return a scoped object
// for the request because this migration request will join the active one once
// scheduled.
auto statusWithMigrationQueryResult =
grid->shardRegistry()->getConfigShard()->exhaustiveFindOnConfig(
opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
repl::ReadConcernLevel::kLocalReadConcern,
MigrationType::ConfigNS,
BSON(MigrationType::name(migrateInfo.getName())),
BSONObj(),
boost::none);
if (!statusWithMigrationQueryResult.isOK()) {
return statusWithMigrationQueryResult.getStatus().withContext(
str::stream() << "Failed to verify whether conflicting migration is in "
<< "progress for migration '"
<< redact(migrateInfo.toString())
<< "' while trying to query config.migrations.");
}
if (statusWithMigrationQueryResult.getValue().docs.empty()) {
// The document that caused the DuplicateKey error is no longer in the collection,
// so retrying the insert might succeed.
continue;
}
invariant(statusWithMigrationQueryResult.getValue().docs.size() == 1);
BSONObj activeMigrationBSON = statusWithMigrationQueryResult.getValue().docs.front();
auto statusWithActiveMigration = MigrationType::fromBSON(activeMigrationBSON);
if (!statusWithActiveMigration.isOK()) {
return statusWithActiveMigration.getStatus().withContext(
str::stream() << "Failed to verify whether conflicting migration is in "
<< "progress for migration '"
<< redact(migrateInfo.toString())
<< "' while trying to parse active migration document '"
<< redact(activeMigrationBSON.toString())
<< "'.");
}
MigrateInfo activeMigrateInfo = statusWithActiveMigration.getValue().toMigrateInfo();
if (activeMigrateInfo.to != migrateInfo.to ||
activeMigrateInfo.from != migrateInfo.from) {
log() << "Failed to write document '" << redact(migrateInfo.toString())
<< "' to config.migrations because there is already an active migration for"
<< " that chunk: '" << redact(activeMigrateInfo.toString()) << "'."
<< causedBy(redact(result));
return result;
}
result = Status::OK();
}
// As long as there isn't a DuplicateKey error, the document may have been written, and it's
// safe (won't delete another migration's document) and necessary to try to clean up the
// document via the destructor.
ScopedMigrationRequest scopedMigrationRequest(opCtx, migrateInfo.nss, migrateInfo.minKey);
// If there was a write error, let the object go out of scope and clean up in the
// destructor.
if (!result.isOK()) {
return result;
}
return std::move(scopedMigrationRequest);
}
return Status(ErrorCodes::OperationFailed,
str::stream() << "Failed to insert the config.migrations document after max "
<< "number of retries. Chunk '"
<< ChunkRange(migrateInfo.minKey, migrateInfo.maxKey).toString()
<< "' in collection '"
<< migrateInfo.nss.ns()
<< "' was being moved (somewhere) by another operation.");
}
ScopedMigrationRequest ScopedMigrationRequest::createForRecovery(OperationContext* opCtx,
const NamespaceString& nss,
const BSONObj& minKey) {
return ScopedMigrationRequest(opCtx, nss, minKey);
}
Status ScopedMigrationRequest::tryToRemoveMigration() {
invariant(_opCtx);
BSONObj migrationDocumentIdentifier =
BSON(MigrationType::ns(_nss.ns()) << MigrationType::min(_minKey));
Status status = Grid::get(_opCtx)->catalogClient()->removeConfigDocuments(
_opCtx, MigrationType::ConfigNS, migrationDocumentIdentifier, kMajorityWriteConcern);
if (status.isOK()) {
// Don't try to do a no-op remove in the destructor.
_opCtx = nullptr;
}
return status;
}
void ScopedMigrationRequest::keepDocumentOnDestruct() {
invariant(_opCtx);
_opCtx = nullptr;
LOG(1) << "Keeping config.migrations document with namespace '" << _nss << "' and minKey '"
<< _minKey << "' for balancer recovery";
}
} // namespace mongo
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