fix(cluster_family): Cancel slot migration from incoming node on OOM

src/server/cluster/cluster_defs.h

@@ -172,12 +172,11 @@ class ClusterShardInfos {
 };
 
 // MigrationState constants are ordered in state changing order
-enum class MigrationState : uint8_t {
-  C_CONNECTING,
-  C_SYNC,
-  C_ERROR,
-  C_FINISHED,
-};
+enum class MigrationState : uint8_t { C_CONNECTING, C_SYNC, C_ERROR, C_FINISHED, C_FATAL };
+
+// Errors during slot migration
+static constexpr std::string_view kUnknownMigration = "UNKNOWN_MIGRATION";
+static constexpr std::string_view kIncomingMigrationOOM = "INCOMING_MIGRATION_OOM";
 
 // return error message if slot doesn't belong to this node
 facade::ErrorReply SlotOwnershipError(SlotId slot_id);

src/server/cluster/cluster_family.cc

@@ -726,6 +726,8 @@ static string_view StateToStr(MigrationState state) {
       return "ERROR"sv;
     case MigrationState::C_FINISHED:
       return "FINISHED"sv;
+    case MigrationState::C_FATAL:
+      return "FATAL"sv;
   }
   DCHECK(false) << "Unknown State value " << static_cast<underlying_type_t<MigrationState>>(state);
   return "UNDEFINED_STATE"sv;
@@ -765,7 +767,6 @@ void ClusterFamily::DflySlotMigrationStatus(CmdArgList args, SinkReplyBuilder* b
   };
 
   for (const auto& m : incoming_migrations_jobs_) {
-    // TODO add error status
     append_answer("in", m->GetSourceID(), node_id, m->GetState(), m->GetKeyCount(),
                   m->GetErrorStr());
   }
@@ -834,7 +835,7 @@ ClusterFamily::TakeOutOutgoingMigrations(shared_ptr<ClusterConfig> new_config,
     removed_slots.Merge(slots);
     LOG(INFO) << "Outgoing migration cancelled: slots " << slots.ToString() << " to "
               << migration.GetHostIp() << ":" << migration.GetPort();
-    migration.Finish();
+    migration.Finish(MigrationState::C_FINISHED);
     res.migrations.push_back(std::move(*it));
     outgoing_migration_jobs_.erase(it);
   }
@@ -925,7 +926,7 @@ void ClusterFamily::InitMigration(CmdArgList args, SinkReplyBuilder* builder) {
 
   if (!migration) {
     VLOG(1) << "Unrecognized incoming migration from " << source_id;
-    return builder->SendSimpleString(OutgoingMigration::kUnknownMigration);
+    return builder->SendSimpleString(kUnknownMigration);
   }
 
   if (migration->GetState() != MigrationState::C_CONNECTING) {
@@ -936,6 +937,10 @@ void ClusterFamily::InitMigration(CmdArgList args, SinkReplyBuilder* builder) {
     DeleteSlots(slots);
   }
 
+  if (migration->GetState() == MigrationState::C_FATAL) {
+    return builder->SendError(absl::StrCat("-", kIncomingMigrationOOM));
+  }
+
   migration->Init(flows_num);
 
   return builder->SendOk();
@@ -955,6 +960,7 @@ void ClusterFamily::DflyMigrateFlow(CmdArgList args, SinkReplyBuilder* builder,
   cntx->conn()->SetName(absl::StrCat("migration_flow_", source_id));
 
   auto migration = GetIncomingMigration(source_id);
+
   if (!migration) {
     return builder->SendError(kIdNotFound);
   }
@@ -1033,15 +1039,19 @@ void ClusterFamily::DflyMigrateAck(CmdArgList args, SinkReplyBuilder* builder) {
                    [source_id = source_id](const auto& m) { return m.node_info.id == source_id; });
   if (m_it == in_migrations.end()) {
     LOG(WARNING) << "migration isn't in config";
-    return builder->SendError(OutgoingMigration::kUnknownMigration);
+    return builder->SendError(kUnknownMigration);
   }
 
   auto migration = GetIncomingMigration(source_id);
   if (!migration)
     return builder->SendError(kIdNotFound);
 
   if (!migration->Join(attempt)) {
-    return builder->SendError("Join timeout happened");
+    if (migration->GetState() == MigrationState::C_FATAL) {
+      return builder->SendError(absl::StrCat("-", kIncomingMigrationOOM));
+    } else {
+      return builder->SendError("Join timeout happened");
+    }
   }
 
   ApplyMigrationSlotRangeToConfig(migration->GetSourceID(), migration->GetSlots(), true);

src/server/cluster/incoming_slot_migration.cc

@@ -70,6 +70,14 @@ class ClusterShardMigration {
         break;
       }
 
+      auto used_mem = used_mem_current.load(memory_order_relaxed);
+      // If aplying transaction data will reach 90% of max_memory_limit we end migration.
+      if ((used_mem + tx_data->command.cmd_len) > (0.9 * max_memory_limit)) {
+        cntx->ReportError(std::string{kIncomingMigrationOOM});
+        in_migration_->ReportFatalError(std::string{kIncomingMigrationOOM});
+        break;
+      }
+
       while (tx_data->opcode == journal::Op::LSN) {
         VLOG(2) << "Attempt to finalize flow " << source_shard_id_ << " attempt " << tx_data->lsn;
         last_attempt_.store(tx_data->lsn);
@@ -79,6 +87,11 @@ class ClusterShardMigration {
           VLOG(1) << "Finalized flow " << source_shard_id_;
           return;
         }
+        if (in_migration_->GetState() == MigrationState::C_FATAL) {
+          VLOG(1) << "Flow finalization " << source_shard_id_
+                  << " canceled due memory limit reached";
+          return;
+        }
         if (!tx_data->command.cmd_args.empty()) {
           VLOG(1) << "Flow finalization failed " << source_shard_id_ << " by "
                   << tx_data->command.cmd_args[0];
@@ -181,6 +194,11 @@ bool IncomingSlotMigration::Join(long attempt) {
       return false;
     }
 
+    // If any of migration shards reported ERROR (OOM) we can return error
+    if (GetState() == MigrationState::C_FATAL) {
+      return false;
+    }
+
     // if data was sent after LSN, WaitFor() always returns false so to reduce wait time
     // we check current state and if WaitFor false but GetLastAttempt() == attempt
     // the Join is failed and we can return false
@@ -218,6 +236,11 @@ void IncomingSlotMigration::Stop() {
     }
   }
 
+  // Don't wait if we reached FATAL state
+  if (state_ == MigrationState::C_FATAL) {
+    return;
+  }
+
   // we need to Join the migration process to prevent data corruption
   const absl::Time start = absl::Now();
   const absl::Duration timeout =
@@ -251,7 +274,12 @@ void IncomingSlotMigration::Init(uint32_t shards_num) {
 
 void IncomingSlotMigration::StartFlow(uint32_t shard, util::FiberSocketBase* source) {
   shard_flows_[shard]->Start(&cntx_, source);
-  VLOG(1) << "Incoming flow " << shard << " finished for " << source_id_;
+  VLOG(1) << "Incoming flow " << shard
+          << (GetState() == MigrationState::C_FINISHED ? " finished " : " cancelled ") << "for "
+          << source_id_;
+  if (GetState() == MigrationState::C_FATAL) {
+    Stop();
+  }
 }
 
 size_t IncomingSlotMigration::GetKeyCount() const {

src/server/cluster/incoming_slot_migration.h

@@ -50,10 +50,20 @@ class IncomingSlotMigration {
     return source_id_;
   }
 
+  // Switch to  FATAL state and store error message
+  void ReportFatalError(dfly::GenericError err) ABSL_LOCKS_EXCLUDED(state_mu_, error_mu_) {
+    errors_count_.fetch_add(1, std::memory_order_relaxed);
+    util::fb2::LockGuard lk_state(state_mu_);
+    util::fb2::LockGuard lk_error(error_mu_);
+    state_ = MigrationState::C_FATAL;
+    last_error_ = std::move(err);
+  }
+
   void ReportError(dfly::GenericError err) ABSL_LOCKS_EXCLUDED(error_mu_) {
     errors_count_.fetch_add(1, std::memory_order_relaxed);
     util::fb2::LockGuard lk(error_mu_);
-    last_error_ = std::move(err);
+    if (GetState() != MigrationState::C_FATAL)
+      last_error_ = std::move(err);
   }
 
   std::string GetErrorStr() const ABSL_LOCKS_EXCLUDED(error_mu_) {
@@ -75,6 +85,7 @@ class IncomingSlotMigration {
   std::vector<std::unique_ptr<ClusterShardMigration>> shard_flows_;
   SlotRanges slots_;
   ExecutionState cntx_;
+
   mutable util::fb2::Mutex error_mu_;
   dfly::GenericError last_error_ ABSL_GUARDED_BY(error_mu_);
   std::atomic<size_t> errors_count_ = 0;

src/server/cluster/outgoing_slot_migration.cc

@@ -36,7 +36,8 @@ class OutgoingMigration::SliceSlotMigration : private ProtocolClient {
   SliceSlotMigration(DbSlice* slice, ServerContext server_context, SlotSet slots,
                      journal::Journal* journal, OutgoingMigration* om)
       : ProtocolClient(server_context), streamer_(slice, std::move(slots), journal, &exec_st_) {
-    exec_st_.SwitchErrorHandler([om](auto ge) { om->Finish(std::move(ge)); });
+    exec_st_.SwitchErrorHandler(
+        [om](auto ge) { om->Finish(MigrationState::C_ERROR, std::move(ge)); });
   }
 
   ~SliceSlotMigration() {
@@ -138,10 +139,8 @@ void OutgoingMigration::OnAllShards(
   });
 }
 
-void OutgoingMigration::Finish(GenericError error) {
-  auto next_state = MigrationState::C_FINISHED;
+void OutgoingMigration::Finish(MigrationState next_state, GenericError error) {
   if (error) {
-    next_state = MigrationState::C_ERROR;
     LOG(WARNING) << "Finish outgoing migration for " << cf_->MyID() << ": "
                  << migration_info_.node_info.id << " with error: " << error.Format();
     exec_st_.ReportError(std::move(error));
@@ -164,6 +163,7 @@ void OutgoingMigration::Finish(GenericError error) {
 
       case MigrationState::C_SYNC:
       case MigrationState::C_ERROR:
+      case MigrationState::C_FATAL:
         should_cancel_flows = true;
         break;
     }
@@ -221,6 +221,14 @@ void OutgoingMigration::SyncFb() {
       continue;
     }
 
+    // Break outgoing migration if INIT from incoming node responded with OOM. Usually this will
+    // happen on second iteration after first failed with OOM. Sending second INIT is required to
+    // cleanup slots on incoming slot migration node.
+    if (CheckRespSimpleError(kIncomingMigrationOOM)) {
+      ChangeState(MigrationState::C_FATAL);
+      break;
+    }
+
     if (!CheckRespIsSimpleReply("OK")) {
       if (CheckRespIsSimpleReply(kUnknownMigration)) {
         const absl::Duration passed = absl::Now() - start_time;
@@ -272,7 +280,11 @@ void OutgoingMigration::SyncFb() {
 
     long attempt = 0;
     while (GetState() != MigrationState::C_FINISHED && !FinalizeMigration(++attempt)) {
-      // process commands that were on pause and try again
+      // Break loop and don't sleep in case of C_FATAL
+      if (GetState() == MigrationState::C_FATAL) {
+        break;
+      }
+      // Process commands that were on pause and try again
       VLOG(1) << "Waiting for migration to finalize...";
       ThisFiber::SleepFor(500ms);
     }
@@ -355,6 +367,12 @@ bool OutgoingMigration::FinalizeMigration(long attempt) {
       return false;
     }
 
+    // Check OOM from incoming slot migration on ACK request
+    if (CheckRespSimpleError(kIncomingMigrationOOM)) {
+      Finish(MigrationState::C_FATAL, std::string(kIncomingMigrationOOM));
+      return false;
+    }
+
     if (!CheckRespFirstTypes({RespExpr::INT64})) {
       LOG(WARNING) << "Incorrect response type for " << cf_->MyID() << " : "
                    << migration_info_.node_info.id << " attempt " << attempt
@@ -371,7 +389,7 @@ bool OutgoingMigration::FinalizeMigration(long attempt) {
   }
 
   if (!exec_st_.GetError()) {
-    Finish();
+    Finish(MigrationState::C_FINISHED);
     keys_number_ = cluster::GetKeyCount(migration_info_.slot_ranges);
     cf_->ApplyMigrationSlotRangeToConfig(migration_info_.node_info.id, migration_info_.slot_ranges,
                                          false);

src/server/cluster/outgoing_slot_migration.h

@@ -30,7 +30,7 @@ class OutgoingMigration : private ProtocolClient {
   // if is_error = false mark migration as FINISHED and cancel migration if it's not finished yet
   // can be called from any thread, but only after Start()
   // if is_error = true and migration is in progress it will be restarted otherwise nothing happens
-  void Finish(GenericError error = {}) ABSL_LOCKS_EXCLUDED(state_mu_);
+  void Finish(MigrationState next_state, GenericError error = {}) ABSL_LOCKS_EXCLUDED(state_mu_);
 
   MigrationState GetState() const ABSL_LOCKS_EXCLUDED(state_mu_);
 
@@ -76,8 +76,6 @@ class OutgoingMigration : private ProtocolClient {
 
   size_t GetKeyCount() const ABSL_LOCKS_EXCLUDED(state_mu_);
 
-  static constexpr std::string_view kUnknownMigration = "UNKNOWN_MIGRATION";
-
  private:
   // should be run for all shards
   void StartFlow(journal::Journal* journal, io::Sink* dest);

src/server/journal/executor.cc

@@ -33,7 +33,7 @@ template <typename... Ts> journal::ParsedEntry::CmdData BuildFromParts(Ts... par
     start += part.size();
   }
 
-  return {std::move(buf), std::move(slice_parts)};
+  return {std::move(buf), std::move(slice_parts), cmd_str.size()};
 }
 }  // namespace
 

src/server/journal/serializer.cc

@@ -162,6 +162,7 @@ std::error_code JournalReader::ReadCommand(journal::ParsedEntry::CmdData* data)
 
   size_t cmd_size = 0;
   SET_OR_RETURN(ReadUInt<uint64_t>(), cmd_size);
+  data->cmd_len = cmd_size;
 
   // Read all strings consecutively.
   data->command_buf = make_unique<uint8_t[]>(cmd_size);
@@ -174,6 +175,9 @@ std::error_code JournalReader::ReadCommand(journal::ParsedEntry::CmdData* data)
     ptr += size;
     cmd_size -= size;
   }
+
+  data->cmd_len -= cmd_size;
+
   return {};
 }
 

src/server/journal/types.h

@@ -73,6 +73,7 @@ struct ParsedEntry : public EntryBase {
   struct CmdData {
     std::unique_ptr<uint8_t[]> command_buf;
     CmdArgVec cmd_args;  // represents the parsed command.
+    size_t cmd_len{0};
   };
   CmdData cmd;
 

src/server/protocol_client.cc

@@ -339,6 +339,11 @@ bool ProtocolClient::CheckRespIsSimpleReply(string_view reply) const {
          ToSV(resp_args_.front().GetBuf()) == reply;
 }
 
+bool ProtocolClient::CheckRespSimpleError(string_view error) const {
+  return resp_args_.size() == 1 && resp_args_.front().type == RespExpr::ERROR &&
+         ToSV(resp_args_.front().GetBuf()) == error;
+}
+
 bool ProtocolClient::CheckRespFirstTypes(initializer_list<RespExpr::Type> types) const {
   unsigned i = 0;
   for (RespExpr::Type type : types) {

src/server/protocol_client.h

@@ -85,6 +85,9 @@ class ProtocolClient {
   // Check if reps_args contains a simple reply.
   bool CheckRespIsSimpleReply(std::string_view reply) const;
 
+  // Check if resp_args contains a simple error
+  bool CheckRespSimpleError(std::string_view error) const;
+
   // Check resp_args contains the following types at front.
   bool CheckRespFirstTypes(std::initializer_list<facade::RespExpr::Type> types) const;