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/**
* Copyright (C) 2016 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/migration_manager.h"
#include <memory>
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/bson/util/bson_extract.h"
#include "mongo/client/remote_command_targeter.h"
#include "mongo/db/client.h"
#include "mongo/db/repl/repl_set_config.h"
#include "mongo/db/repl/replication_coordinator.h"
#include "mongo/db/s/balancer/scoped_migration_request.h"
#include "mongo/db/s/balancer/type_migration.h"
#include "mongo/executor/task_executor_pool.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/s/catalog/sharding_catalog_client.h"
#include "mongo/s/catalog_cache.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/grid.h"
#include "mongo/s/move_chunk_request.h"
#include "mongo/util/log.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
using executor::RemoteCommandRequest;
using executor::RemoteCommandResponse;
using std::shared_ptr;
using std::vector;
using str::stream;
namespace {
const char kChunkTooBig[] = "chunkTooBig"; // TODO: delete in 3.8
const WriteConcernOptions kMajorityWriteConcern(WriteConcernOptions::kMajority,
WriteConcernOptions::SyncMode::UNSET,
Seconds(15));
/**
* Parses the 'commandResponse' and converts it to a status to use as the outcome of the command.
* Preserves backwards compatibility with 3.4 and earlier shards that, rather than use a ChunkTooBig
* error code, include an extra field in the response.
*
* TODO: Delete in 3.8
*/
Status extractMigrationStatusFromCommandResponse(const BSONObj& commandResponse) {
Status commandStatus = getStatusFromCommandResult(commandResponse);
if (!commandStatus.isOK()) {
bool chunkTooBig = false;
bsonExtractBooleanFieldWithDefault(commandResponse, kChunkTooBig, false, &chunkTooBig)
.transitional_ignore();
if (chunkTooBig) {
commandStatus = {ErrorCodes::ChunkTooBig, commandStatus.reason()};
}
}
return commandStatus;
}
/**
* Returns whether the specified status is an error caused by stepdown of the primary config node
* currently running the balancer.
*/
bool isErrorDueToConfigStepdown(Status status, bool isStopping) {
return ((status == ErrorCodes::CallbackCanceled && isStopping) ||
status == ErrorCodes::BalancerInterrupted ||
status == ErrorCodes::InterruptedDueToReplStateChange);
}
} // namespace
MigrationManager::MigrationManager(ServiceContext* serviceContext)
: _serviceContext(serviceContext) {}
MigrationManager::~MigrationManager() {
// The migration manager must be completely quiesced at destruction time
invariant(_activeMigrations.empty());
}
MigrationStatuses MigrationManager::executeMigrationsForAutoBalance(
OperationContext* opCtx,
const vector<MigrateInfo>& migrateInfos,
uint64_t maxChunkSizeBytes,
const MigrationSecondaryThrottleOptions& secondaryThrottle,
bool waitForDelete) {
MigrationStatuses migrationStatuses;
{
std::map<MigrationIdentifier, ScopedMigrationRequest> scopedMigrationRequests;
vector<std::pair<shared_ptr<Notification<RemoteCommandResponse>>, MigrateInfo>> responses;
for (const auto& migrateInfo : migrateInfos) {
// Write a document to the config.migrations collection, in case this migration must be
// recovered by the Balancer. Fail if the chunk is already moving.
auto statusWithScopedMigrationRequest =
ScopedMigrationRequest::writeMigration(opCtx, migrateInfo, waitForDelete);
if (!statusWithScopedMigrationRequest.isOK()) {
migrationStatuses.emplace(migrateInfo.getName(),
std::move(statusWithScopedMigrationRequest.getStatus()));
continue;
}
scopedMigrationRequests.emplace(migrateInfo.getName(),
std::move(statusWithScopedMigrationRequest.getValue()));
responses.emplace_back(
_schedule(opCtx, migrateInfo, maxChunkSizeBytes, secondaryThrottle, waitForDelete),
migrateInfo);
}
// Wait for all the scheduled migrations to complete.
for (auto& response : responses) {
auto notification = std::move(response.first);
auto migrateInfo = std::move(response.second);
const auto& remoteCommandResponse = notification->get();
auto it = scopedMigrationRequests.find(migrateInfo.getName());
invariant(it != scopedMigrationRequests.end());
Status commandStatus =
_processRemoteCommandResponse(remoteCommandResponse, &it->second);
migrationStatuses.emplace(migrateInfo.getName(), std::move(commandStatus));
}
}
invariant(migrationStatuses.size() == migrateInfos.size());
return migrationStatuses;
}
Status MigrationManager::executeManualMigration(
OperationContext* opCtx,
const MigrateInfo& migrateInfo,
uint64_t maxChunkSizeBytes,
const MigrationSecondaryThrottleOptions& secondaryThrottle,
bool waitForDelete) {
_waitForRecovery();
// Write a document to the config.migrations collection, in case this migration must be
// recovered by the Balancer. Fail if the chunk is already moving.
auto statusWithScopedMigrationRequest =
ScopedMigrationRequest::writeMigration(opCtx, migrateInfo, waitForDelete);
if (!statusWithScopedMigrationRequest.isOK()) {
return statusWithScopedMigrationRequest.getStatus();
}
RemoteCommandResponse remoteCommandResponse =
_schedule(opCtx, migrateInfo, maxChunkSizeBytes, secondaryThrottle, waitForDelete)->get();
auto routingInfoStatus =
Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(
opCtx, migrateInfo.ns);
if (!routingInfoStatus.isOK()) {
return routingInfoStatus.getStatus();
}
auto& routingInfo = routingInfoStatus.getValue();
auto chunk = routingInfo.cm()->findIntersectingChunkWithSimpleCollation(migrateInfo.minKey);
invariant(chunk);
Status commandStatus = _processRemoteCommandResponse(
remoteCommandResponse, &statusWithScopedMigrationRequest.getValue());
// Migration calls can be interrupted after the metadata is committed but before the command
// finishes the waitForDelete stage. Any failovers, therefore, must always cause the moveChunk
// command to be retried so as to assure that the waitForDelete promise of a successful command
// has been fulfilled.
if (chunk->getShardId() == migrateInfo.to && commandStatus != ErrorCodes::BalancerInterrupted) {
return Status::OK();
}
return commandStatus;
}
void MigrationManager::startRecoveryAndAcquireDistLocks(OperationContext* opCtx) {
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
invariant(_state == State::kStopped);
invariant(_migrationRecoveryMap.empty());
_state = State::kRecovering;
}
auto scopedGuard = MakeGuard([&] {
_migrationRecoveryMap.clear();
_abandonActiveMigrationsAndEnableManager(opCtx);
});
auto distLockManager = Grid::get(opCtx)->catalogClient()->getDistLockManager();
// Load the active migrations from the config.migrations collection.
auto statusWithMigrationsQueryResponse =
Grid::get(opCtx)->shardRegistry()->getConfigShard()->exhaustiveFindOnConfig(
opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
repl::ReadConcernLevel::kLocalReadConcern,
NamespaceString(MigrationType::ConfigNS),
BSONObj(),
BSONObj(),
boost::none);
if (!statusWithMigrationsQueryResponse.isOK()) {
log() << "Unable to read config.migrations collection documents for balancer migration"
<< " recovery. Abandoning balancer recovery."
<< causedBy(redact(statusWithMigrationsQueryResponse.getStatus()));
return;
}
for (const BSONObj& migration : statusWithMigrationsQueryResponse.getValue().docs) {
auto statusWithMigrationType = MigrationType::fromBSON(migration);
if (!statusWithMigrationType.isOK()) {
// The format of this migration document is incorrect. The balancer holds a distlock for
// this migration, but without parsing the migration document we cannot identify which
// distlock must be released. So we must release all distlocks.
log() << "Unable to parse config.migrations document '" << redact(migration.toString())
<< "' for balancer migration recovery. Abandoning balancer recovery."
<< causedBy(redact(statusWithMigrationType.getStatus()));
return;
}
MigrationType migrateType = std::move(statusWithMigrationType.getValue());
auto it = _migrationRecoveryMap.find(NamespaceString(migrateType.getNss()));
if (it == _migrationRecoveryMap.end()) {
std::list<MigrationType> list;
it = _migrationRecoveryMap.insert(std::make_pair(migrateType.getNss(), list)).first;
// Reacquire the matching distributed lock for this namespace.
const std::string whyMessage(stream() << "Migrating chunk(s) in collection "
<< migrateType.getNss().ns());
auto statusWithDistLockHandle = distLockManager->tryLockWithLocalWriteConcern(
opCtx, migrateType.getNss().ns(), whyMessage, _lockSessionID);
if (!statusWithDistLockHandle.isOK()) {
log() << "Failed to acquire distributed lock for collection '"
<< migrateType.getNss().ns()
<< "' during balancer recovery of an active migration. Abandoning"
<< " balancer recovery."
<< causedBy(redact(statusWithDistLockHandle.getStatus()));
return;
}
}
it->second.push_back(std::move(migrateType));
}
scopedGuard.Dismiss();
}
void MigrationManager::finishRecovery(OperationContext* opCtx,
uint64_t maxChunkSizeBytes,
const MigrationSecondaryThrottleOptions& secondaryThrottle) {
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_state == State::kStopping) {
_migrationRecoveryMap.clear();
return;
}
// If recovery was abandoned in startRecovery, then there is no more to do.
if (_state == State::kEnabled) {
invariant(_migrationRecoveryMap.empty());
return;
}
invariant(_state == State::kRecovering);
}
auto scopedGuard = MakeGuard([&] {
_migrationRecoveryMap.clear();
_abandonActiveMigrationsAndEnableManager(opCtx);
});
// Schedule recovered migrations.
vector<ScopedMigrationRequest> scopedMigrationRequests;
vector<shared_ptr<Notification<RemoteCommandResponse>>> responses;
for (auto& nssAndMigrateInfos : _migrationRecoveryMap) {
auto& nss = nssAndMigrateInfos.first;
auto& migrateInfos = nssAndMigrateInfos.second;
invariant(!migrateInfos.empty());
auto routingInfoStatus =
Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx,
nss);
if (!routingInfoStatus.isOK()) {
// This shouldn't happen because the collection was intact and sharded when the previous
// config primary was active and the dist locks have been held by the balancer
// throughout. Abort migration recovery.
log() << "Unable to reload chunk metadata for collection '" << nss
<< "' during balancer recovery. Abandoning recovery."
<< causedBy(redact(routingInfoStatus.getStatus()));
return;
}
auto& routingInfo = routingInfoStatus.getValue();
int scheduledMigrations = 0;
while (!migrateInfos.empty()) {
auto migrationType = std::move(migrateInfos.front());
const auto migrationInfo = migrationType.toMigrateInfo();
auto waitForDelete = migrationType.getWaitForDelete();
migrateInfos.pop_front();
auto chunk =
routingInfo.cm()->findIntersectingChunkWithSimpleCollation(migrationInfo.minKey);
invariant(chunk);
if (chunk->getShardId() != migrationInfo.from) {
// Chunk is no longer on the source shard specified by this migration. Erase the
// migration recovery document associated with it.
ScopedMigrationRequest::createForRecovery(opCtx, nss, migrationInfo.minKey);
continue;
}
scopedMigrationRequests.emplace_back(
ScopedMigrationRequest::createForRecovery(opCtx, nss, migrationInfo.minKey));
scheduledMigrations++;
responses.emplace_back(_schedule(
opCtx, migrationInfo, maxChunkSizeBytes, secondaryThrottle, waitForDelete));
}
// If no migrations were scheduled for this namespace, free the dist lock
if (!scheduledMigrations) {
Grid::get(opCtx)->catalogClient()->getDistLockManager()->unlock(
opCtx, _lockSessionID, nss.ns());
}
}
_migrationRecoveryMap.clear();
scopedGuard.Dismiss();
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_state == State::kRecovering) {
_state = State::kEnabled;
_condVar.notify_all();
}
}
// Wait for each migration to finish, as usual.
for (auto& response : responses) {
response->get();
}
}
void MigrationManager::interruptAndDisableMigrations() {
executor::TaskExecutor* const executor =
Grid::get(_serviceContext)->getExecutorPool()->getFixedExecutor();
stdx::lock_guard<stdx::mutex> lock(_mutex);
invariant(_state == State::kEnabled || _state == State::kRecovering);
_state = State::kStopping;
// Interrupt any active migrations with dist lock
for (auto& cmsEntry : _activeMigrations) {
auto& migrations = cmsEntry.second;
for (auto& migration : migrations) {
if (migration.callbackHandle) {
executor->cancel(*migration.callbackHandle);
}
}
}
_checkDrained(lock);
}
void MigrationManager::drainActiveMigrations() {
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_state == State::kStopped)
return;
invariant(_state == State::kStopping);
_condVar.wait(lock, [this] { return _activeMigrations.empty(); });
_state = State::kStopped;
}
shared_ptr<Notification<RemoteCommandResponse>> MigrationManager::_schedule(
OperationContext* opCtx,
const MigrateInfo& migrateInfo,
uint64_t maxChunkSizeBytes,
const MigrationSecondaryThrottleOptions& secondaryThrottle,
bool waitForDelete) {
const NamespaceString nss(migrateInfo.ns);
// Ensure we are not stopped in order to avoid doing the extra work
{
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_state != State::kEnabled && _state != State::kRecovering) {
return std::make_shared<Notification<RemoteCommandResponse>>(
Status(ErrorCodes::BalancerInterrupted,
"Migration cannot be executed because the balancer is not running"));
}
}
const auto fromShardStatus =
Grid::get(opCtx)->shardRegistry()->getShard(opCtx, migrateInfo.from);
if (!fromShardStatus.isOK()) {
return std::make_shared<Notification<RemoteCommandResponse>>(
std::move(fromShardStatus.getStatus()));
}
const auto fromShard = fromShardStatus.getValue();
auto fromHostStatus = fromShard->getTargeter()->findHost(
opCtx, ReadPreferenceSetting{ReadPreference::PrimaryOnly});
if (!fromHostStatus.isOK()) {
return std::make_shared<Notification<RemoteCommandResponse>>(
std::move(fromHostStatus.getStatus()));
}
BSONObjBuilder builder;
MoveChunkRequest::appendAsCommand(
&builder,
nss,
migrateInfo.version,
repl::ReplicationCoordinator::get(opCtx)->getConfig().getConnectionString(),
migrateInfo.from,
migrateInfo.to,
ChunkRange(migrateInfo.minKey, migrateInfo.maxKey),
maxChunkSizeBytes,
secondaryThrottle,
waitForDelete);
stdx::lock_guard<stdx::mutex> lock(_mutex);
if (_state != State::kEnabled && _state != State::kRecovering) {
return std::make_shared<Notification<RemoteCommandResponse>>(
Status(ErrorCodes::BalancerInterrupted,
"Migration cannot be executed because the balancer is not running"));
}
Migration migration(nss, builder.obj());
auto retVal = migration.completionNotification;
_schedule(lock, opCtx, fromHostStatus.getValue(), std::move(migration));
return retVal;
}
void MigrationManager::_schedule(WithLock lock,
OperationContext* opCtx,
const HostAndPort& targetHost,
Migration migration) {
executor::TaskExecutor* const executor =
Grid::get(opCtx)->getExecutorPool()->getFixedExecutor();
const NamespaceString nss(migration.nss);
auto it = _activeMigrations.find(nss);
if (it == _activeMigrations.end()) {
const std::string whyMessage(stream() << "Migrating chunk(s) in collection " << nss.ns());
// Acquire the collection distributed lock (blocking call)
auto statusWithDistLockHandle =
Grid::get(opCtx)->catalogClient()->getDistLockManager()->lockWithSessionID(
opCtx,
nss.ns(),
whyMessage,
_lockSessionID,
DistLockManager::kSingleLockAttemptTimeout);
if (!statusWithDistLockHandle.isOK()) {
migration.completionNotification->set(
Status(statusWithDistLockHandle.getStatus().code(),
stream() << "Could not acquire collection lock for " << nss.ns()
<< " to migrate chunks, due to "
<< statusWithDistLockHandle.getStatus().reason()));
return;
}
it = _activeMigrations.insert(std::make_pair(nss, MigrationsList())).first;
}
auto migrations = &it->second;
// Add ourselves to the list of migrations on this collection
migrations->push_front(std::move(migration));
auto itMigration = migrations->begin();
const RemoteCommandRequest remoteRequest(
targetHost, NamespaceString::kAdminDb.toString(), itMigration->moveChunkCmdObj, opCtx);
StatusWith<executor::TaskExecutor::CallbackHandle> callbackHandleWithStatus =
executor->scheduleRemoteCommand(
remoteRequest,
[this, itMigration](const executor::TaskExecutor::RemoteCommandCallbackArgs& args) {
Client::initThread(getThreadName());
ON_BLOCK_EXIT([&] { Client::destroy(); });
auto opCtx = cc().makeOperationContext();
stdx::lock_guard<stdx::mutex> lock(_mutex);
_complete(lock, opCtx.get(), itMigration, args.response);
});
if (callbackHandleWithStatus.isOK()) {
itMigration->callbackHandle = std::move(callbackHandleWithStatus.getValue());
return;
}
_complete(lock, opCtx, itMigration, std::move(callbackHandleWithStatus.getStatus()));
}
void MigrationManager::_complete(WithLock lock,
OperationContext* opCtx,
MigrationsList::iterator itMigration,
const RemoteCommandResponse& remoteCommandResponse) {
const NamespaceString nss(itMigration->nss);
// Make sure to signal the notification last, after the distributed lock is freed, so that we
// don't have the race condition where a subsequently scheduled migration finds the dist lock
// still acquired.
auto notificationToSignal = itMigration->completionNotification;
auto it = _activeMigrations.find(nss);
invariant(it != _activeMigrations.end());
auto migrations = &it->second;
migrations->erase(itMigration);
if (migrations->empty()) {
Grid::get(opCtx)->catalogClient()->getDistLockManager()->unlock(
opCtx, _lockSessionID, nss.ns());
_activeMigrations.erase(it);
_checkDrained(lock);
}
notificationToSignal->set(remoteCommandResponse);
}
void MigrationManager::_checkDrained(WithLock) {
if (_state == State::kEnabled || _state == State::kRecovering) {
return;
}
invariant(_state == State::kStopping);
if (_activeMigrations.empty()) {
_condVar.notify_all();
}
}
void MigrationManager::_waitForRecovery() {
stdx::unique_lock<stdx::mutex> lock(_mutex);
_condVar.wait(lock, [this] { return _state != State::kRecovering; });
}
void MigrationManager::_abandonActiveMigrationsAndEnableManager(OperationContext* opCtx) {
stdx::unique_lock<stdx::mutex> lock(_mutex);
if (_state == State::kStopping) {
// The balancer was interrupted. Let the next balancer recover the state.
return;
}
invariant(_state == State::kRecovering);
auto catalogClient = Grid::get(opCtx)->catalogClient();
// Unlock all balancer distlocks we aren't using anymore.
auto distLockManager = catalogClient->getDistLockManager();
distLockManager->unlockAll(opCtx, distLockManager->getProcessID());
// Clear the config.migrations collection so that those chunks can be scheduled for migration
// again.
catalogClient
->removeConfigDocuments(opCtx, MigrationType::ConfigNS, BSONObj(), kMajorityWriteConcern)
.transitional_ignore();
_state = State::kEnabled;
_condVar.notify_all();
}
Status MigrationManager::_processRemoteCommandResponse(
const RemoteCommandResponse& remoteCommandResponse,
ScopedMigrationRequest* scopedMigrationRequest) {
stdx::lock_guard<stdx::mutex> lock(_mutex);
Status commandStatus(ErrorCodes::InternalError, "Uninitialized value.");
// Check for local errors sending the remote command caused by stepdown.
if (isErrorDueToConfigStepdown(remoteCommandResponse.status,
_state != State::kEnabled && _state != State::kRecovering)) {
scopedMigrationRequest->keepDocumentOnDestruct();
return {ErrorCodes::BalancerInterrupted,
stream() << "Migration interrupted because the balancer is stopping."
<< " Command status: "
<< remoteCommandResponse.status.toString()};
}
if (!remoteCommandResponse.isOK()) {
commandStatus = remoteCommandResponse.status;
} else {
// TODO: delete in 3.8
commandStatus = extractMigrationStatusFromCommandResponse(remoteCommandResponse.data);
}
if (!Shard::shouldErrorBePropagated(commandStatus.code())) {
commandStatus = {ErrorCodes::OperationFailed,
stream() << "moveChunk command failed on source shard."
<< causedBy(commandStatus)};
}
// Any failure to remove the migration document should be because the config server is
// stepping/shutting down. In this case we must fail the moveChunk command with a retryable
// error so that the caller does not move on to other distlock requiring operations that could
// fail when the balancer recovers and takes distlocks for migration recovery.
Status status = scopedMigrationRequest->tryToRemoveMigration();
if (!status.isOK()) {
commandStatus = {
ErrorCodes::BalancerInterrupted,
stream() << "Migration interrupted because the balancer is stopping"
<< " and failed to remove the config.migrations document."
<< " Command status: "
<< (commandStatus.isOK() ? status.toString() : commandStatus.toString())};
}
return commandStatus;
}
MigrationManager::Migration::Migration(NamespaceString inNss, BSONObj inMoveChunkCmdObj)
: nss(std::move(inNss)),
moveChunkCmdObj(std::move(inMoveChunkCmdObj)),
completionNotification(std::make_shared<Notification<RemoteCommandResponse>>()) {}
MigrationManager::Migration::~Migration() {
invariant(completionNotification);
}
} // namespace mongo
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