diff options
Diffstat (limited to 'src/mongo/db/s/balancer/balancer_policy.cpp')
| -rw-r--r-- | src/mongo/db/s/balancer/balancer_policy.cpp | 265 |
1 files changed, 39 insertions, 226 deletions
diff --git a/src/mongo/db/s/balancer/balancer_policy.cpp b/src/mongo/db/s/balancer/balancer_policy.cpp index 7677a0e0d23..3587c61bacf 100644 --- a/src/mongo/db/s/balancer/balancer_policy.cpp +++ b/src/mongo/db/s/balancer/balancer_policy.cpp @@ -58,14 +58,6 @@ using std::string; using std::vector; using namespace fmt::literals; -namespace { - -// This value indicates the minimum deviation shard's number of chunks need to have from the -// optimal average across all shards for a zone for a rebalancing migration to be initiated. -const size_t kDefaultImbalanceThreshold = 1; - -} // namespace - DistributionStatus::DistributionStatus(NamespaceString nss, ShardToChunksMap shardToChunksMap, ZoneInfo zoneInfo) @@ -73,46 +65,11 @@ DistributionStatus::DistributionStatus(NamespaceString nss, _shardChunks(std::move(shardToChunksMap)), _zoneInfo(std::move(zoneInfo)) {} -size_t DistributionStatus::totalChunks() const { - size_t total = 0; - - for (const auto& shardChunk : _shardChunks) { - total += shardChunk.second.size(); - } - - return total; -} - -size_t DistributionStatus::totalChunksInZone(const std::string& zone) const { - size_t total = 0; - - for (const auto& shardChunk : _shardChunks) { - total += numberOfChunksInShardWithZone(shardChunk.first, zone); - } - - return total; -} - size_t DistributionStatus::numberOfChunksInShard(const ShardId& shardId) const { const auto& shardChunks = getChunks(shardId); return shardChunks.size(); } -size_t DistributionStatus::numberOfChunksInShardWithZone(const ShardId& shardId, - const string& zone) const { - const auto& shardChunks = getChunks(shardId); - - size_t total = 0; - - for (const auto& chunk : shardChunks) { - if (zone == getZoneForChunk(chunk)) { - total++; - } - } - - return total; -} - const vector<ChunkType>& DistributionStatus::getChunks(const ShardId& shardId) const { ShardToChunksMap::const_iterator i = _shardChunks.find(shardId); invariant(i != _shardChunks.end()); @@ -242,14 +199,12 @@ Status BalancerPolicy::isShardSuitableReceiver(const ClusterStatistics::ShardSta std::tuple<ShardId, int64_t> BalancerPolicy::_getLeastLoadedReceiverShard( const ShardStatisticsVector& shardStats, const DistributionStatus& distribution, - const boost::optional<CollectionDataSizeInfoForBalancing>& collDataSizeInfo, + const CollectionDataSizeInfoForBalancing& collDataSizeInfo, const string& zone, const stdx::unordered_set<ShardId>& availableShards) { ShardId best; int64_t currentMin = numeric_limits<int64_t>::max(); - const auto shouldBalanceAccordingToDataSize = collDataSizeInfo.has_value(); - for (const auto& stat : shardStats) { if (!availableShards.count(stat.shardId)) continue; @@ -259,24 +214,16 @@ std::tuple<ShardId, int64_t> BalancerPolicy::_getLeastLoadedReceiverShard( continue; } - if (shouldBalanceAccordingToDataSize) { - const auto& shardSizeIt = collDataSizeInfo->shardToDataSizeMap.find(stat.shardId); - if (shardSizeIt == collDataSizeInfo->shardToDataSizeMap.end()) { - // Skip if stats not available (may happen if add|remove shard during a round) - continue; - } + const auto& shardSizeIt = collDataSizeInfo.shardToDataSizeMap.find(stat.shardId); + if (shardSizeIt == collDataSizeInfo.shardToDataSizeMap.end()) { + // Skip if stats not available (may happen if add|remove shard during a round) + continue; + } - int64_t shardSize = shardSizeIt->second; - if (shardSize < currentMin) { - best = stat.shardId; - currentMin = shardSize; - } - } else { - int64_t myChunks = distribution.numberOfChunksInShard(stat.shardId); - if (myChunks < currentMin) { - best = stat.shardId; - currentMin = myChunks; - } + const auto shardSize = shardSizeIt->second; + if (shardSize < currentMin) { + best = stat.shardId; + currentMin = shardSize; } } @@ -286,37 +233,26 @@ std::tuple<ShardId, int64_t> BalancerPolicy::_getLeastLoadedReceiverShard( std::tuple<ShardId, int64_t> BalancerPolicy::_getMostOverloadedShard( const ShardStatisticsVector& shardStats, const DistributionStatus& distribution, - const boost::optional<CollectionDataSizeInfoForBalancing>& collDataSizeInfo, + const CollectionDataSizeInfoForBalancing& collDataSizeInfo, const string& chunkZone, const stdx::unordered_set<ShardId>& availableShards) { ShardId worst; long long currentMax = numeric_limits<long long>::min(); - const auto shouldBalanceAccordingToDataSize = collDataSizeInfo.has_value(); - for (const auto& stat : shardStats) { if (!availableShards.count(stat.shardId)) continue; - if (shouldBalanceAccordingToDataSize) { - const auto& shardSizeIt = collDataSizeInfo->shardToDataSizeMap.find(stat.shardId); - if (shardSizeIt == collDataSizeInfo->shardToDataSizeMap.end()) { - // Skip if stats not available (may happen if add|remove shard during a round) - continue; - } + const auto& shardSizeIt = collDataSizeInfo.shardToDataSizeMap.find(stat.shardId); + if (shardSizeIt == collDataSizeInfo.shardToDataSizeMap.end()) { + // Skip if stats not available (may happen if add|remove shard during a round) + continue; + } - const auto shardSize = shardSizeIt->second; - if (shardSize > currentMax) { - worst = stat.shardId; - currentMax = shardSize; - } - } else { - const unsigned shardChunkCount = - distribution.numberOfChunksInShardWithZone(stat.shardId, chunkZone); - if (shardChunkCount > currentMax) { - worst = stat.shardId; - currentMax = shardChunkCount; - } + const auto shardSize = shardSizeIt->second; + if (shardSize > currentMax) { + worst = stat.shardId; + currentMax = shardSize; } } @@ -391,7 +327,7 @@ MigrateInfo chooseRandomMigration(const ShardStatisticsVector& shardStats, MigrateInfosWithReason BalancerPolicy::balance( const ShardStatisticsVector& shardStats, const DistributionStatus& distribution, - const boost::optional<CollectionDataSizeInfoForBalancing>& collDataSizeInfo, + const CollectionDataSizeInfoForBalancing& collDataSizeInfo, stdx::unordered_set<ShardId>* availableShards, bool forceJumbo) { vector<MigrateInfo> migrations; @@ -453,15 +389,11 @@ MigrateInfosWithReason BalancerPolicy::balance( invariant(to != stat.shardId); - auto maxChunkSizeBytes = [&]() -> boost::optional<int64_t> { - if (collDataSizeInfo.has_value()) { - return collDataSizeInfo->maxChunkSizeBytes; - } - return boost::none; - }(); - - migrations.emplace_back( - to, distribution.nss(), chunk, ForceJumbo::kForceBalancer, maxChunkSizeBytes); + migrations.emplace_back(to, + distribution.nss(), + chunk, + ForceJumbo::kForceBalancer, + collDataSizeInfo.maxChunkSizeBytes); if (firstReason == MigrationReason::none) { firstReason = MigrationReason::drain; } @@ -530,19 +462,12 @@ MigrateInfosWithReason BalancerPolicy::balance( invariant(to != stat.shardId); - auto maxChunkSizeBytes = [&]() -> boost::optional<int64_t> { - if (collDataSizeInfo.has_value()) { - return collDataSizeInfo->maxChunkSizeBytes; - } - return boost::none; - }(); - migrations.emplace_back(to, distribution.nss(), chunk, forceJumbo ? ForceJumbo::kForceBalancer : ForceJumbo::kDoNotForce, - maxChunkSizeBytes); + collDataSizeInfo.maxChunkSizeBytes); if (firstReason == MigrationReason::none) { firstReason = MigrationReason::zoneViolation; } @@ -589,29 +514,14 @@ MigrateInfosWithReason BalancerPolicy::balance( continue; } - auto singleZoneBalance = [&]() { - if (collDataSizeInfo.has_value()) { - return _singleZoneBalanceBasedOnDataSize(shardStats, - distribution, - *collDataSizeInfo, - zone, - &migrations, - availableShards, - forceJumbo ? ForceJumbo::kForceBalancer - : ForceJumbo::kDoNotForce); - } - - return _singleZoneBalanceBasedOnChunks(shardStats, - distribution, - zone, - totalNumberOfShardsWithZone, - &migrations, - availableShards, - forceJumbo ? ForceJumbo::kForceBalancer - : ForceJumbo::kDoNotForce); - }; - - while (singleZoneBalance()) { + while (_singleZoneBalanceBasedOnDataSize(shardStats, + distribution, + collDataSizeInfo, + zone, + &migrations, + availableShards, + forceJumbo ? ForceJumbo::kForceBalancer + : ForceJumbo::kDoNotForce)) { if (firstReason == MigrationReason::none) { firstReason = MigrationReason::chunksImbalance; } @@ -624,14 +534,12 @@ MigrateInfosWithReason BalancerPolicy::balance( boost::optional<MigrateInfo> BalancerPolicy::balanceSingleChunk( const ChunkType& chunk, const ShardStatisticsVector& shardStats, - const DistributionStatus& distribution) { + const DistributionStatus& distribution, + const CollectionDataSizeInfoForBalancing& collDataSizeInfo) { const string zone = distribution.getZoneForChunk(chunk); - const auto [newShardId, _] = _getLeastLoadedReceiverShard(shardStats, - distribution, - boost::none /* collDataSizeInfo */, - zone, - stdx::unordered_set<ShardId>()); + const auto [newShardId, _] = _getLeastLoadedReceiverShard( + shardStats, distribution, collDataSizeInfo, zone, stdx::unordered_set<ShardId>()); if (!newShardId.isValid() || newShardId == chunk.getShard()) { return boost::optional<MigrateInfo>(); } @@ -639,101 +547,6 @@ boost::optional<MigrateInfo> BalancerPolicy::balanceSingleChunk( return MigrateInfo(newShardId, distribution.nss(), chunk, ForceJumbo::kDoNotForce); } -bool BalancerPolicy::_singleZoneBalanceBasedOnChunks(const ShardStatisticsVector& shardStats, - const DistributionStatus& distribution, - const string& zone, - size_t totalNumberOfShardsWithZone, - vector<MigrateInfo>* migrations, - stdx::unordered_set<ShardId>* availableShards, - ForceJumbo forceJumbo) { - // Calculate the rounded optimal number of chunks per shard - const size_t totalNumberOfChunksInZone = - (zone.empty() ? distribution.totalChunks() : distribution.totalChunksInZone(zone)); - const size_t idealNumberOfChunksPerShardForZone = - (size_t)std::roundf(totalNumberOfChunksInZone / (float)totalNumberOfShardsWithZone); - - const auto [from, fromSize] = - _getMostOverloadedShard(shardStats, distribution, boost::none, zone, *availableShards); - if (!from.isValid()) - return false; - - const size_t max = distribution.numberOfChunksInShardWithZone(from, zone); - - // Do not use a shard if it already has less entries than the optimal per-shard chunk count - if (max <= idealNumberOfChunksPerShardForZone) - return false; - - const auto [to, toSize] = - _getLeastLoadedReceiverShard(shardStats, distribution, boost::none, zone, *availableShards); - if (!to.isValid()) { - if (migrations->empty()) { - LOGV2(21882, "No available shards to take chunks for zone", "zone"_attr = zone); - } - return false; - } - - const size_t min = distribution.numberOfChunksInShardWithZone(to, zone); - - // Do not use a shard if it already has more entries than the optimal per-shard chunk count - if (min >= idealNumberOfChunksPerShardForZone) - return false; - - const size_t imbalance = max - idealNumberOfChunksPerShardForZone; - - LOGV2_DEBUG( - 21883, - 1, - "collection: {namespace}, zone: {zone}, donor: {fromShardId} chunks on " - " {fromShardChunkCount}, receiver: {toShardId} chunks on {toShardChunkCount}, " - "ideal: {idealNumberOfChunksPerShardForZone}, threshold: {chunkCountImbalanceThreshold}", - "Balancing single zone", - "namespace"_attr = distribution.nss().ns(), - "zone"_attr = zone, - "fromShardId"_attr = from, - "fromShardChunkCount"_attr = max, - "toShardId"_attr = to, - "toShardChunkCount"_attr = min, - "idealNumberOfChunksPerShardForZone"_attr = idealNumberOfChunksPerShardForZone, - "chunkCountImbalanceThreshold"_attr = kDefaultImbalanceThreshold); - - // Check whether it is necessary to balance within this zone - if (imbalance < kDefaultImbalanceThreshold) - return false; - - const vector<ChunkType>& chunks = distribution.getChunks(from); - - unsigned numJumboChunks = 0; - - for (const auto& chunk : chunks) { - if (distribution.getZoneForChunk(chunk) != zone) - continue; - - if (chunk.getJumbo()) { - numJumboChunks++; - continue; - } - - migrations->emplace_back(to, distribution.nss(), chunk, forceJumbo); - invariant(availableShards->erase(chunk.getShard())); - invariant(availableShards->erase(to)); - return true; - } - - if (numJumboChunks) { - LOGV2_WARNING( - 21894, - "Shard: {shardId}, collection: {namespace} has only jumbo chunks for " - "zone \'{zone}\' and cannot be balanced. Jumbo chunks count: {numJumboChunks}", - "Shard has only jumbo chunks for and cannot be balanced", - "shardId"_attr = from, - "namespace"_attr = distribution.nss().ns(), - "zone"_attr = zone, - "numJumboChunks"_attr = numJumboChunks); - } - - return false; -} - bool BalancerPolicy::_singleZoneBalanceBasedOnDataSize( const ShardStatisticsVector& shardStats, const DistributionStatus& distribution, |