/
balancer.cpp
1158 lines (987 loc) · 47.9 KB
/
balancer.cpp
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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.
*/
#include "mongo/db/s/balancer/balancer.h"
#include <algorithm>
#include <memory>
#include <pcrecpp.h>
#include <string>
#include "mongo/base/status_with.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/client/read_preference.h"
#include "mongo/db/catalog/collection_catalog.h"
#include "mongo/db/client.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/db/s/balancer/balancer_chunk_selection_policy_impl.h"
#include "mongo/db/s/balancer/balancer_commands_scheduler_impl.h"
#include "mongo/db/s/balancer/balancer_defragmentation_policy_impl.h"
#include "mongo/db/s/balancer/cluster_chunks_resize_policy_impl.h"
#include "mongo/db/s/balancer/cluster_statistics_impl.h"
#include "mongo/db/s/config/sharding_catalog_manager.h"
#include "mongo/db/s/sharding_config_server_parameters_gen.h"
#include "mongo/db/s/sharding_logging.h"
#include "mongo/executor/scoped_task_executor.h"
#include "mongo/logv2/log.h"
#include "mongo/s/balancer_configuration.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/balancer_collection_status_gen.h"
#include "mongo/s/request_types/configure_collection_balancing_gen.h"
#include "mongo/s/shard_util.h"
#include "mongo/s/sharding_feature_flags_gen.h"
#include "mongo/util/concurrency/idle_thread_block.h"
#include "mongo/util/exit.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/timer.h"
#include "mongo/util/version.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding
namespace mongo {
using std::map;
using std::string;
using std::vector;
namespace {
MONGO_FAIL_POINT_DEFINE(overrideBalanceRoundInterval);
const Seconds kBalanceRoundDefaultInterval(10);
// Sleep between balancer rounds in the case where the last round found some chunks which needed to
// be balanced. This value should be set sufficiently low so that imbalanced clusters will quickly
// reach balanced state, but setting it too low may cause CRUD operations to start failing due to
// not being able to establish a stable shard version.
const Seconds kShortBalanceRoundInterval(1);
/**
* Balancer status response
*/
static constexpr StringData kBalancerPolicyStatusDraining = "draining"_sd;
static constexpr StringData kBalancerPolicyStatusZoneViolation = "zoneViolation"_sd;
static constexpr StringData kBalancerPolicyStatusChunksImbalance = "chunksImbalance"_sd;
static constexpr StringData kBalancerPolicyStatusDefragmentingChunks = "defragmentingChunks"_sd;
/**
* Utility class to generate timing and statistics for a single balancer round.
*/
class BalanceRoundDetails {
public:
BalanceRoundDetails() : _executionTimer() {}
void setSucceeded(int candidateChunks, int chunksMoved) {
invariant(!_errMsg);
_candidateChunks = candidateChunks;
_chunksMoved = chunksMoved;
}
void setFailed(const string& errMsg) {
_errMsg = errMsg;
}
BSONObj toBSON() const {
BSONObjBuilder builder;
builder.append("executionTimeMillis", _executionTimer.millis());
builder.append("errorOccurred", _errMsg.is_initialized());
if (_errMsg) {
builder.append("errmsg", *_errMsg);
} else {
builder.append("candidateChunks", _candidateChunks);
builder.append("chunksMoved", _chunksMoved);
}
return builder.obj();
}
private:
const Timer _executionTimer;
// Set only on success
int _candidateChunks{0};
int _chunksMoved{0};
// Set only on failure
boost::optional<string> _errMsg;
};
/**
* Occasionally prints a log message with shard versions if the versions are not the same
* in the cluster.
*/
void warnOnMultiVersion(const vector<ClusterStatistics::ShardStatistics>& clusterStats) {
static const auto& majorMinorRE = *new pcrecpp::RE(R"re(^(\d+)\.(\d+)\.)re");
auto&& vii = VersionInfoInterface::instance();
auto hasMyVersion = [&](auto&& stat) {
int major;
int minor;
return majorMinorRE.PartialMatch(pcrecpp::StringPiece(stat.mongoVersion), &major, &minor) &&
major == vii.majorVersion() && minor == vii.minorVersion();
};
// If we're all the same version, don't message
if (std::all_of(clusterStats.begin(), clusterStats.end(), hasMyVersion))
return;
BSONObjBuilder shardVersions;
for (const auto& stat : clusterStats) {
shardVersions << stat.shardId << stat.mongoVersion;
}
LOGV2_WARNING(21875,
"Multiversion cluster detected",
"localVersion"_attr = vii.version(),
"shardVersions"_attr = shardVersions.done());
}
Status processManualMigrationOutcome(OperationContext* opCtx,
const BSONObj& chunkMin,
const NamespaceString& nss,
const ShardId& destination,
Status outcome) {
// Since the commands scheduler uses a separate thread to remotely execute a
// request, the resulting clusterTime needs to be explicitly retrieved and set on the
// original context of the requestor to ensure it will be propagated back to the router.
auto& replClient = repl::ReplClientInfo::forClient(opCtx->getClient());
replClient.setLastOpToSystemLastOpTime(opCtx);
if (outcome.isOK()) {
return outcome;
}
auto swCM =
Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx, nss);
if (!swCM.isOK()) {
return swCM.getStatus();
}
const auto currentChunkInfo =
swCM.getValue().findIntersectingChunkWithSimpleCollation(chunkMin);
if (currentChunkInfo.getShardId() == destination &&
outcome != ErrorCodes::BalancerInterrupted) {
// 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.
LOGV2(6036622,
"Migration outcome is not OK, but the transaction was committed. Returning success");
outcome = Status::OK();
}
return outcome;
}
uint64_t getMaxChunkSizeBytes(OperationContext* opCtx, const CollectionType& coll) {
const auto balancerConfig = Grid::get(opCtx)->getBalancerConfiguration();
uassertStatusOK(balancerConfig->refreshAndCheck(opCtx));
return coll.getMaxChunkSizeBytes().value_or(balancerConfig->getMaxChunkSizeBytes());
}
int64_t getMaxChunkSizeMB(OperationContext* opCtx, const CollectionType& coll) {
return getMaxChunkSizeBytes(opCtx, coll) / (1024 * 1024);
}
// Returns a boolean flag indicating whether secondary throttling is enabled and the write concern
// to apply for migrations
std::tuple<bool, WriteConcernOptions> getSecondaryThrottleAndWriteConcern(
const boost::optional<MigrationSecondaryThrottleOptions>& secondaryThrottle) {
if (secondaryThrottle &&
secondaryThrottle->getSecondaryThrottle() == MigrationSecondaryThrottleOptions::kOn) {
if (secondaryThrottle->isWriteConcernSpecified()) {
return {true, secondaryThrottle->getWriteConcern()};
}
return {true, WriteConcernOptions()};
}
return {false, WriteConcernOptions()};
}
const auto _balancerDecoration = ServiceContext::declareDecoration<Balancer>();
const ReplicaSetAwareServiceRegistry::Registerer<Balancer> _balancerRegisterer("Balancer");
} // namespace
Balancer* Balancer::get(ServiceContext* serviceContext) {
return &_balancerDecoration(serviceContext);
}
Balancer* Balancer::get(OperationContext* operationContext) {
return get(operationContext->getServiceContext());
}
Balancer::Balancer()
: _balancedLastTime(0),
_random(std::random_device{}()),
_clusterStats(std::make_unique<ClusterStatisticsImpl>(_random)),
_chunkSelectionPolicy(
std::make_unique<BalancerChunkSelectionPolicyImpl>(_clusterStats.get(), _random)),
_commandScheduler(std::make_unique<BalancerCommandsSchedulerImpl>()),
_defragmentationPolicy(std::make_unique<BalancerDefragmentationPolicyImpl>(
_clusterStats.get(), _random, [this]() { _onActionsStreamPolicyStateUpdate(); })),
_clusterChunksResizePolicy(std::make_unique<ClusterChunksResizePolicyImpl>(
[this] { _onActionsStreamPolicyStateUpdate(); })) {}
Balancer::~Balancer() {
// Terminate the balancer thread so it doesn't leak memory.
interruptBalancer();
waitForBalancerToStop();
}
void Balancer::onStepUpBegin(OperationContext* opCtx, long long term) {
// Before starting step-up, ensure the balancer is ready to start. Specifically, that the
// balancer is actually stopped, because it may still be in the process of stopping if this
// node was previously primary.
waitForBalancerToStop();
}
void Balancer::onStepUpComplete(OperationContext* opCtx, long long term) {
initiateBalancer(opCtx);
}
void Balancer::onStepDown() {
interruptBalancer();
}
void Balancer::onBecomeArbiter() {
// The Balancer is only active on config servers, and arbiters are not permitted in config
// server replica sets.
MONGO_UNREACHABLE;
}
void Balancer::initiateBalancer(OperationContext* opCtx) {
stdx::lock_guard<Latch> scopedLock(_mutex);
invariant(_state == kStopped);
_state = kRunning;
invariant(!_thread.joinable());
invariant(!_actionStreamConsumerThread.joinable());
invariant(!_threadOperationContext);
_thread = stdx::thread([this] { _mainThread(); });
}
void Balancer::interruptBalancer() {
stdx::lock_guard<Latch> scopedLock(_mutex);
if (_state != kRunning)
return;
_state = kStopping;
_thread.detach();
// Interrupt the balancer thread if it has been started. We are guaranteed that the operation
// context of that thread is still alive, because we hold the balancer mutex.
if (_threadOperationContext) {
stdx::lock_guard<Client> scopedClientLock(*_threadOperationContext->getClient());
_threadOperationContext->markKilled(ErrorCodes::InterruptedDueToReplStateChange);
}
_condVar.notify_all();
_defragmentationCondVar.notify_all();
}
void Balancer::waitForBalancerToStop() {
stdx::unique_lock<Latch> scopedLock(_mutex);
_joinCond.wait(scopedLock, [this] { return _state == kStopped; });
}
void Balancer::joinCurrentRound(OperationContext* opCtx) {
stdx::unique_lock<Latch> scopedLock(_mutex);
const auto numRoundsAtStart = _numBalancerRounds;
opCtx->waitForConditionOrInterrupt(_condVar, scopedLock, [&] {
return !_inBalancerRound || _numBalancerRounds != numRoundsAtStart;
});
}
Status Balancer::rebalanceSingleChunk(OperationContext* opCtx,
const NamespaceString& nss,
const ChunkType& chunk) {
auto migrateStatus = _chunkSelectionPolicy->selectSpecificChunkToMove(opCtx, nss, chunk);
if (!migrateStatus.isOK()) {
return migrateStatus.getStatus();
}
auto migrateInfo = std::move(migrateStatus.getValue());
if (!migrateInfo) {
LOGV2_DEBUG(21854,
1,
"Unable to find more appropriate location for chunk {chunk}",
"Unable to find more appropriate location for chunk",
"chunk"_attr = redact(chunk.toString()));
return Status::OK();
}
auto balancerConfig = Grid::get(opCtx)->getBalancerConfiguration();
Status refreshStatus = balancerConfig->refreshAndCheck(opCtx);
if (!refreshStatus.isOK()) {
return refreshStatus;
}
auto coll = Grid::get(opCtx)->catalogClient()->getCollection(
opCtx, nss, repl::ReadConcernLevel::kMajorityReadConcern);
auto maxChunkSize =
coll.getMaxChunkSizeBytes().value_or(balancerConfig->getMaxChunkSizeBytes());
MoveChunkSettings settings(
maxChunkSize, balancerConfig->getSecondaryThrottle(), balancerConfig->waitForDelete());
auto response =
_commandScheduler
->requestMoveChunk(opCtx, *migrateInfo, settings, true /* issuedByRemoteUser */)
.getNoThrow(opCtx);
return processManualMigrationOutcome(opCtx, chunk.getMin(), nss, migrateInfo->to, response);
}
Status Balancer::moveSingleChunk(OperationContext* opCtx,
const NamespaceString& nss,
const ChunkType& chunk,
const ShardId& newShardId,
const MigrationSecondaryThrottleOptions& secondaryThrottle,
bool waitForDelete,
bool forceJumbo) {
auto moveAllowedStatus = _chunkSelectionPolicy->checkMoveAllowed(opCtx, chunk, newShardId);
if (!moveAllowedStatus.isOK()) {
return moveAllowedStatus;
}
auto coll = Grid::get(opCtx)->catalogClient()->getCollection(
opCtx, nss, repl::ReadConcernLevel::kMajorityReadConcern);
const auto maxChunkSize = getMaxChunkSizeBytes(opCtx, coll);
MoveChunkSettings settings(maxChunkSize, secondaryThrottle, waitForDelete);
MigrateInfo migrateInfo(newShardId,
nss,
chunk,
forceJumbo ? MoveChunkRequest::ForceJumbo::kForceManual
: MoveChunkRequest::ForceJumbo::kDoNotForce);
auto response =
_commandScheduler
->requestMoveChunk(opCtx, migrateInfo, settings, true /* issuedByRemoteUser */)
.getNoThrow(opCtx);
return processManualMigrationOutcome(opCtx, chunk.getMin(), nss, newShardId, response);
}
Status Balancer::moveRange(OperationContext* opCtx,
const NamespaceString& nss,
const ConfigsvrMoveRange& request,
bool issuedByRemoteUser) {
auto coll = Grid::get(opCtx)->catalogClient()->getCollection(
opCtx, nss, repl::ReadConcernLevel::kMajorityReadConcern);
const auto maxChunkSize = getMaxChunkSizeBytes(opCtx, coll);
const auto [fromShardId, min] = [&]() {
const auto cm = uassertStatusOK(
Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(opCtx,
nss));
// TODO SERVER-64926 do not assume min always present
const auto& chunk = cm.findIntersectingChunkWithSimpleCollation(*request.getMin());
return std::tuple<ShardId, BSONObj>{chunk.getShardId(), chunk.getMin()};
}();
ShardsvrMoveRange shardSvrRequest(nss);
shardSvrRequest.setDbName(NamespaceString::kAdminDb);
shardSvrRequest.setMoveRangeRequestBase(request.getMoveRangeRequestBase());
shardSvrRequest.setMaxChunkSizeBytes(maxChunkSize);
shardSvrRequest.setFromShard(fromShardId);
shardSvrRequest.setEpoch(coll.getEpoch());
const auto [secondaryThrottle, wc] =
getSecondaryThrottleAndWriteConcern(request.getSecondaryThrottle());
shardSvrRequest.setSecondaryThrottle(secondaryThrottle);
shardSvrRequest.setForceJumbo(request.getForceJumbo());
auto response =
_commandScheduler->requestMoveRange(opCtx, shardSvrRequest, wc, issuedByRemoteUser)
.getNoThrow(opCtx);
return processManualMigrationOutcome(
opCtx, min, nss, shardSvrRequest.getToShard(), std::move(response));
}
void Balancer::report(OperationContext* opCtx, BSONObjBuilder* builder) {
auto balancerConfig = Grid::get(opCtx)->getBalancerConfiguration();
balancerConfig->refreshAndCheck(opCtx).ignore();
const auto mode = balancerConfig->getBalancerMode();
stdx::lock_guard<Latch> scopedLock(_mutex);
builder->append("mode", BalancerSettingsType::kBalancerModes[mode]);
builder->append("inBalancerRound", _inBalancerRound);
builder->append("numBalancerRounds", _numBalancerRounds);
}
void Balancer::_consumeActionStreamLoop() {
ScopeGuard onExitCleanup([this] {
_defragmentationPolicy->interruptAllDefragmentations();
_clusterChunksResizePolicy->stop();
});
Client::initThread("BalancerSecondary");
auto opCtx = cc().makeOperationContext();
// This thread never refreshes balancerConfig - instead, it relies on the requests
// performed by _mainThread() on each round to eventually see updated information.
auto balancerConfig = Grid::get(opCtx.get())->getBalancerConfiguration();
executor::ScopedTaskExecutor executor(
Grid::get(opCtx.get())->getExecutorPool()->getFixedExecutor());
auto selectStream = [&]() -> ActionsStreamPolicy* {
// This policy has higher priority - and once activated, it cannot be disabled through cfg
// changes.
if (_clusterChunksResizePolicy->isActive()) {
return _clusterChunksResizePolicy.get();
}
if (balancerConfig->shouldBalanceForAutoSplit()) {
return _defragmentationPolicy.get();
}
return nullptr;
};
auto applyActionResponseTo = [this](const DefragmentationAction& action,
const DefragmentationActionResponse& response,
ActionsStreamPolicy* policy) {
invariant(_outstandingStreamingOps.addAndFetch(-1) >= 0);
ThreadClient tc("BalancerSecondaryThread::applyActionResponse", getGlobalServiceContext());
auto opCtx = tc->makeOperationContext();
policy->applyActionResult(opCtx.get(), action, response);
};
auto applyThrottling = [lastActionTime = Date_t::fromMillisSinceEpoch(0)]() mutable {
const Milliseconds throttle{chunkDefragmentationThrottlingMS.load()};
auto timeSinceLastAction = Date_t::now() - lastActionTime;
if (throttle > timeSinceLastAction) {
auto sleepingTime = throttle - timeSinceLastAction;
LOGV2_DEBUG(6443700,
2,
"Applying throttling on balancer secondary thread",
"sleepingTime"_attr = sleepingTime);
// TODO SERVER-64865 interrupt the sleep when a shutwdown request is received
sleepFor(sleepingTime);
}
lastActionTime = Date_t::now();
};
ActionsStreamPolicy* selectedStream(nullptr);
bool streamDrained = false;
while (true) {
bool newStreamSelected = false;
{
stdx::unique_lock<Latch> ul(_mutex);
_defragmentationCondVar.wait(ul, [&] {
auto nextSelection = selectStream();
if (nextSelection != selectedStream) {
newStreamSelected = true;
selectedStream = nextSelection;
streamDrained = false;
}
auto canConsumeStream = selectedStream != nullptr &&
_outstandingStreamingOps.load() <= kMaxOutstandingStreamingOperations;
return _state != kRunning ||
(canConsumeStream && (!streamDrained || _newInfoOnStreamingActions.load()));
});
if (_state != kRunning) {
break;
}
}
if (newStreamSelected) {
LOGV2(6417110,
"New actions stream source selected",
"selectedStream"_attr = selectedStream->getName());
}
_newInfoOnStreamingActions.store(false);
auto nextAction = selectedStream->getNextStreamingAction(opCtx.get());
if ((streamDrained = !nextAction.is_initialized())) {
continue;
}
_outstandingStreamingOps.fetchAndAdd(1);
stdx::visit(
visit_helper::Overloaded{
[&, selectedStream](MergeInfo&& mergeAction) {
applyThrottling();
auto result =
_commandScheduler
->requestMergeChunks(opCtx.get(),
mergeAction.nss,
mergeAction.shardId,
mergeAction.chunkRange,
mergeAction.collectionVersion)
.thenRunOn(*executor)
.onCompletion([this,
selectedStream,
&applyActionResponseTo,
action = std::move(mergeAction)](const Status& status) {
applyActionResponseTo(action, status, selectedStream);
});
},
[&, selectedStream](DataSizeInfo&& dataSizeAction) {
auto result =
_commandScheduler
->requestDataSize(opCtx.get(),
dataSizeAction.nss,
dataSizeAction.shardId,
dataSizeAction.chunkRange,
dataSizeAction.version,
dataSizeAction.keyPattern,
dataSizeAction.estimatedValue)
.thenRunOn(*executor)
.onCompletion([this,
selectedStream,
&applyActionResponseTo,
action = std::move(dataSizeAction)](
const StatusWith<DataSizeResponse>& swDataSize) {
applyActionResponseTo(action, swDataSize, selectedStream);
});
},
[&, selectedStream](AutoSplitVectorInfo&& splitVectorAction) {
auto result =
_commandScheduler
->requestAutoSplitVector(opCtx.get(),
splitVectorAction.nss,
splitVectorAction.shardId,
splitVectorAction.keyPattern,
splitVectorAction.minKey,
splitVectorAction.maxKey,
splitVectorAction.maxChunkSizeBytes)
.thenRunOn(*executor)
.onCompletion(
[this,
selectedStream,
&applyActionResponseTo,
action = std::move(splitVectorAction)](
const StatusWith<AutoSplitVectorResponse>& swSplitPoints) {
applyActionResponseTo(action, swSplitPoints, selectedStream);
});
},
[&, selectedStream](SplitInfoWithKeyPattern&& splitAction) {
applyThrottling();
auto result =
_commandScheduler
->requestSplitChunk(opCtx.get(),
splitAction.info.nss,
splitAction.info.shardId,
splitAction.info.collectionVersion,
splitAction.keyPattern,
splitAction.info.minKey,
splitAction.info.maxKey,
splitAction.info.splitKeys)
.thenRunOn(*executor)
.onCompletion([this,
selectedStream,
&applyActionResponseTo,
action = std::move(splitAction)](const Status& status) {
applyActionResponseTo(action, status, selectedStream);
});
},
[](MigrateInfo&& _) {
uasserted(ErrorCodes::BadValue,
"Migrations cannot be processed as Streaming Actions");
}},
std::move(*nextAction));
}
}
void Balancer::_mainThread() {
ON_BLOCK_EXIT([this] {
stdx::lock_guard<Latch> scopedLock(_mutex);
_state = kStopped;
_joinCond.notify_all();
LOGV2_DEBUG(21855, 1, "Balancer thread terminated");
});
Client::initThread("Balancer");
auto opCtx = cc().makeOperationContext();
auto shardingContext = Grid::get(opCtx.get());
LOGV2(21856, "CSRS balancer is starting");
{
stdx::lock_guard<Latch> scopedLock(_mutex);
_threadOperationContext = opCtx.get();
}
const Seconds kInitBackoffInterval(10);
auto balancerConfig = shardingContext->getBalancerConfiguration();
while (!_stopRequested()) {
Status refreshStatus = balancerConfig->refreshAndCheck(opCtx.get());
if (!refreshStatus.isOK()) {
LOGV2_WARNING(
21876,
"Balancer settings could not be loaded because of {error} and will be retried in "
"{backoffInterval}",
"Got error while refreshing balancer settings, will retry with a backoff",
"backoffInterval"_attr = Milliseconds(kInitBackoffInterval),
"error"_attr = refreshStatus);
_sleepFor(opCtx.get(), kInitBackoffInterval);
continue;
}
break;
}
LOGV2(6036605, "Starting command scheduler");
_commandScheduler->start(
opCtx.get(),
MigrationsRecoveryDefaultValues(balancerConfig->getMaxChunkSizeBytes(),
balancerConfig->getSecondaryThrottle()));
_actionStreamConsumerThread = stdx::thread([&] { _consumeActionStreamLoop(); });
LOGV2(6036606, "Balancer worker thread initialised. Entering main loop.");
// Main balancer loop
while (!_stopRequested()) {
BalanceRoundDetails roundDetails;
_beginRound(opCtx.get());
try {
shardingContext->shardRegistry()->reload(opCtx.get());
uassert(13258, "oids broken after resetting!", _checkOIDs(opCtx.get()));
Status refreshStatus = balancerConfig->refreshAndCheck(opCtx.get());
if (!refreshStatus.isOK()) {
LOGV2_WARNING(21877,
"Skipping balancing round due to {error}",
"Skipping balancing round",
"error"_attr = refreshStatus);
_endRound(opCtx.get(), kBalanceRoundDefaultInterval);
continue;
}
if (!balancerConfig->shouldBalance() || _stopRequested() ||
_clusterChunksResizePolicy->isActive()) {
LOGV2_DEBUG(21859, 1, "Skipping balancing round because balancing is disabled");
_endRound(opCtx.get(), kBalanceRoundDefaultInterval);
continue;
}
// The current configuration is allowing the balancer to perform operations.
// Unblock the secondary thread if needed.
_defragmentationCondVar.notify_all();
{
LOGV2_DEBUG(21860,
1,
"Start balancing round. waitForDelete: {waitForDelete}, "
"secondaryThrottle: {secondaryThrottle}",
"Start balancing round",
"waitForDelete"_attr = balancerConfig->waitForDelete(),
"secondaryThrottle"_attr =
balancerConfig->getSecondaryThrottle().toBSON());
static Occasionally sampler;
if (sampler.tick()) {
warnOnMultiVersion(uassertStatusOK(_clusterStats->getStats(opCtx.get())));
}
// Collect and apply up-to-date configuration values on the cluster collections.
{
OperationContext* ctx = opCtx.get();
auto allCollections = Grid::get(ctx)->catalogClient()->getCollections(ctx, {});
for (const auto& coll : allCollections) {
_defragmentationPolicy->startCollectionDefragmentation(ctx, coll);
}
}
Status status = _splitChunksIfNeeded(opCtx.get());
if (!status.isOK()) {
LOGV2_WARNING(21878,
"Failed to split chunks due to {error}",
"Failed to split chunks",
"error"_attr = status);
} else {
LOGV2_DEBUG(21861, 1, "Done enforcing tag range boundaries.");
}
stdx::unordered_set<ShardId> usedShards;
const auto chunksToDefragment =
_defragmentationPolicy->selectChunksToMove(opCtx.get(), &usedShards);
const auto chunksToRebalance = uassertStatusOK(
_chunkSelectionPolicy->selectChunksToMove(opCtx.get(), &usedShards));
if (chunksToRebalance.empty() && chunksToDefragment.empty()) {
LOGV2_DEBUG(21862, 1, "No need to move any chunk");
_balancedLastTime = 0;
} else {
_balancedLastTime =
_moveChunks(opCtx.get(), chunksToRebalance, chunksToDefragment);
roundDetails.setSucceeded(
static_cast<int>(chunksToRebalance.size() + chunksToDefragment.size()),
_balancedLastTime);
ShardingLogging::get(opCtx.get())
->logAction(opCtx.get(), "balancer.round", "", roundDetails.toBSON())
.ignore();
}
LOGV2_DEBUG(21863, 1, "End balancing round");
}
Milliseconds balancerInterval =
_balancedLastTime ? kShortBalanceRoundInterval : kBalanceRoundDefaultInterval;
overrideBalanceRoundInterval.execute([&](const BSONObj& data) {
balancerInterval = Milliseconds(data["intervalMs"].numberInt());
LOGV2(21864,
"overrideBalanceRoundInterval: using shorter balancing interval: "
"{balancerInterval}",
"overrideBalanceRoundInterval: using shorter balancing interval",
"balancerInterval"_attr = balancerInterval);
});
_endRound(opCtx.get(), balancerInterval);
} catch (const DBException& e) {
LOGV2(21865,
"caught exception while doing balance: {error}",
"Error while doing balance",
"error"_attr = e);
// Just to match the opening statement if in log level 1
LOGV2_DEBUG(21866, 1, "End balancing round");
// This round failed, tell the world!
roundDetails.setFailed(e.what());
ShardingLogging::get(opCtx.get())
->logAction(opCtx.get(), "balancer.round", "", roundDetails.toBSON())
.ignore();
// Sleep a fair amount before retrying because of the error
_endRound(opCtx.get(), kBalanceRoundDefaultInterval);
}
}
{
stdx::lock_guard<Latch> scopedLock(_mutex);
invariant(_state == kStopping);
}
_commandScheduler->stop();
_actionStreamConsumerThread.join();
{
stdx::lock_guard<Latch> scopedLock(_mutex);
_threadOperationContext = nullptr;
}
LOGV2(21867, "CSRS balancer is now stopped");
}
bool Balancer::_stopRequested() {
stdx::lock_guard<Latch> scopedLock(_mutex);
return (_state != kRunning);
}
void Balancer::_beginRound(OperationContext* opCtx) {
stdx::unique_lock<Latch> lock(_mutex);
_inBalancerRound = true;
_condVar.notify_all();
}
void Balancer::_endRound(OperationContext* opCtx, Milliseconds waitTimeout) {
{
stdx::lock_guard<Latch> lock(_mutex);
_inBalancerRound = false;
_numBalancerRounds++;
_condVar.notify_all();
}
MONGO_IDLE_THREAD_BLOCK;
_sleepFor(opCtx, waitTimeout);
}
void Balancer::_sleepFor(OperationContext* opCtx, Milliseconds waitTimeout) {
stdx::unique_lock<Latch> lock(_mutex);
_condVar.wait_for(lock, waitTimeout.toSystemDuration(), [&] { return _state != kRunning; });
}
bool Balancer::_checkOIDs(OperationContext* opCtx) {
auto shardingContext = Grid::get(opCtx);
const auto all = shardingContext->shardRegistry()->getAllShardIdsNoReload();
// map of OID machine ID => shardId
map<int, ShardId> oids;
for (const ShardId& shardId : all) {
if (_stopRequested()) {
return false;
}
auto shardStatus = shardingContext->shardRegistry()->getShard(opCtx, shardId);
if (!shardStatus.isOK()) {
continue;
}
const auto s = shardStatus.getValue();
auto result = uassertStatusOK(
s->runCommandWithFixedRetryAttempts(opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
"admin",
BSON("features" << 1),
Seconds(30),
Shard::RetryPolicy::kIdempotent));
uassertStatusOK(result.commandStatus);
BSONObj f = std::move(result.response);
if (f["oidMachine"].isNumber()) {
int x = f["oidMachine"].numberInt();
if (oids.count(x) == 0) {
oids[x] = shardId;
} else {
LOGV2(21868,
"error: 2 machines have {oidMachine} as oid machine piece: {firstShardId} "
"and {secondShardId}",
"Two machines have the same oidMachine value",
"oidMachine"_attr = x,
"firstShardId"_attr = shardId,
"secondShardId"_attr = oids[x]);
result = uassertStatusOK(s->runCommandWithFixedRetryAttempts(
opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
"admin",
BSON("features" << 1 << "oidReset" << 1),
Seconds(30),
Shard::RetryPolicy::kIdempotent));
uassertStatusOK(result.commandStatus);
auto otherShardStatus = shardingContext->shardRegistry()->getShard(opCtx, oids[x]);
if (otherShardStatus.isOK()) {
result = uassertStatusOK(
otherShardStatus.getValue()->runCommandWithFixedRetryAttempts(
opCtx,
ReadPreferenceSetting{ReadPreference::PrimaryOnly},
"admin",
BSON("features" << 1 << "oidReset" << 1),
Seconds(30),
Shard::RetryPolicy::kIdempotent));
uassertStatusOK(result.commandStatus);
}
return false;
}
} else {
LOGV2(21869,
"warning: oidMachine not set on: {shard}",
"warning: oidMachine not set on shard",
"shard"_attr = s->toString());
}
}
return true;
}
Status Balancer::_splitChunksIfNeeded(OperationContext* opCtx) {
auto chunksToSplitStatus = _chunkSelectionPolicy->selectChunksToSplit(opCtx);
if (!chunksToSplitStatus.isOK()) {
return chunksToSplitStatus.getStatus();
}
for (const auto& splitInfo : chunksToSplitStatus.getValue()) {
auto routingInfoStatus =
Grid::get(opCtx)->catalogCache()->getShardedCollectionRoutingInfoWithRefresh(
opCtx, splitInfo.nss);
if (!routingInfoStatus.isOK()) {
return routingInfoStatus.getStatus();
}
const auto& cm = routingInfoStatus.getValue();
auto splitStatus =
shardutil::splitChunkAtMultiplePoints(opCtx,
splitInfo.shardId,
splitInfo.nss,
cm.getShardKeyPattern(),
splitInfo.collectionVersion.epoch(),
splitInfo.collectionVersion.getTimestamp(),
ChunkVersion::IGNORED() /*shardVersion*/,
ChunkRange(splitInfo.minKey, splitInfo.maxKey),
splitInfo.splitKeys);
if (!splitStatus.isOK()) {
LOGV2_WARNING(21879,
"Failed to split chunk {splitInfo} {error}",
"Failed to split chunk",
"splitInfo"_attr = redact(splitInfo.toString()),
"error"_attr = redact(splitStatus.getStatus()));
}
}
return Status::OK();
}
int Balancer::_moveChunks(OperationContext* opCtx,
const MigrateInfoVector& chunksToRebalance,
const MigrateInfoVector& chunksToDefragment) {
auto balancerConfig = Grid::get(opCtx)->getBalancerConfiguration();
auto catalogClient = Grid::get(opCtx)->catalogClient();
// If the balancer was disabled since we started this round, don't start new chunk moves
if (_stopRequested() || !balancerConfig->shouldBalance() ||
_clusterChunksResizePolicy->isActive()) {
LOGV2_DEBUG(21870, 1, "Skipping balancing round because balancer was stopped");
return 0;
}
std::vector<std::pair<const MigrateInfo&, SemiFuture<void>>> rebalanceMigrationsAndResponses,
defragmentationMigrationsAndResponses;
auto requestMigration = [&](const MigrateInfo& migrateInfo) -> SemiFuture<void> {
auto maxChunkSizeBytes = [&]() {
if (migrateInfo.optMaxChunkSizeBytes.has_value()) {
return *migrateInfo.optMaxChunkSizeBytes;
}
auto coll = Grid::get(opCtx)->catalogClient()->getCollection(
opCtx, migrateInfo.nss, repl::ReadConcernLevel::kMajorityReadConcern);
return coll.getMaxChunkSizeBytes().value_or(balancerConfig->getMaxChunkSizeBytes());
}();
if (serverGlobalParams.featureCompatibility.isLessThan(
multiversion::FeatureCompatibilityVersion::kVersion_6_0)) {
// TODO SERVER-65322 only use `moveRange` once v6.0 branches out
MoveChunkSettings settings(maxChunkSizeBytes,
balancerConfig->getSecondaryThrottle(),
balancerConfig->waitForDelete());
return _commandScheduler->requestMoveChunk(opCtx, migrateInfo, settings);
}
MoveRangeRequestBase requestBase(migrateInfo.to);
requestBase.setWaitForDelete(balancerConfig->waitForDelete());
requestBase.setMin(migrateInfo.minKey);
requestBase.setMax(migrateInfo.maxKey);
ShardsvrMoveRange shardSvrRequest(migrateInfo.nss);
shardSvrRequest.setDbName(NamespaceString::kAdminDb);
shardSvrRequest.setMoveRangeRequestBase(requestBase);
shardSvrRequest.setMaxChunkSizeBytes(maxChunkSizeBytes);
shardSvrRequest.setFromShard(migrateInfo.from);
shardSvrRequest.setEpoch(migrateInfo.version.epoch());
const auto [secondaryThrottle, wc] =
getSecondaryThrottleAndWriteConcern(balancerConfig->getSecondaryThrottle());