Use read-write thread pools

src/main/java/it/cavallium/rockserver/core/client/EmbeddedConnection.java

@@ -4,6 +4,8 @@ import it.cavallium.rockserver.core.common.*;
 import it.cavallium.rockserver.core.common.RequestType.RequestGet;
 import it.cavallium.rockserver.core.common.RequestType.RequestPut;
 import it.cavallium.rockserver.core.impl.EmbeddedDB;
+import it.cavallium.rockserver.core.impl.InternalConnection;
+import it.cavallium.rockserver.core.impl.RWScheduler;
 import java.io.IOException;
 import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
@@ -13,6 +15,7 @@ import java.util.List;
 import java.util.Optional;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.stream.Stream;
@@ -21,16 +24,14 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.reactivestreams.Publisher;
 
-public class EmbeddedConnection extends BaseConnection implements RocksDBAPI {
+public class EmbeddedConnection extends BaseConnection implements RocksDBAPI, InternalConnection {
 
 	private final EmbeddedDB db;
 	public static final URI PRIVATE_MEMORY_URL = URI.create("memory://private");
-	private final ExecutorService exeuctor;
 
 	public EmbeddedConnection(@Nullable Path path, String name, @Nullable Path embeddedConfig) throws IOException {
 		super(name);
 		this.db = new EmbeddedDB(path, name, embeddedConfig);
-		this.exeuctor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
 	}
 
 	@Override
@@ -95,7 +96,8 @@ public class EmbeddedConnection extends BaseConnection implements RocksDBAPI {
 		return (RA) switch (req) {
 			case RocksDBAPICommand.RocksDBAPICommandSingle.PutBatch putBatch -> this.putBatchAsync(putBatch.columnId(), putBatch.batchPublisher(), putBatch.mode());
 			case RocksDBAPICommand.RocksDBAPICommandStream.GetRange<?> getRange -> this.getRangeAsync(getRange.arena(), getRange.transactionId(), getRange.columnId(), getRange.startKeysInclusive(), getRange.endKeysExclusive(), getRange.reverse(), getRange.requestType(), getRange.timeoutMs());
-			case RocksDBAPICommand.RocksDBAPICommandSingle<?> _ -> CompletableFuture.supplyAsync(() -> req.handleSync(this), exeuctor);
+			case RocksDBAPICommand.RocksDBAPICommandSingle<?> _ -> CompletableFuture.supplyAsync(() -> req.handleSync(this),
+					(req.isReadOnly() ? db.getScheduler().readExecutor() : db.getScheduler().writeExecutor()));
 			case RocksDBAPICommand.RocksDBAPICommandStream<?> _ -> throw RocksDBException.of(RocksDBException.RocksDBErrorType.NOT_IMPLEMENTED, "The request of type " + req.getClass().getName() + " is not implemented in class " + this.getClass().getName());
 		};
 	}
@@ -187,4 +189,9 @@ public class EmbeddedConnection extends BaseConnection implements RocksDBAPI {
 	public <T> Publisher<T> getRangeAsync(Arena arena, long transactionId, long columnId, @Nullable Keys startKeysInclusive, @Nullable Keys endKeysExclusive, boolean reverse, RequestType.RequestGetRange<? super KV, T> requestType, long timeoutMs) throws RocksDBException {
 		return db.getRangeAsyncInternal(arena, transactionId, columnId, startKeysInclusive, endKeysExclusive, reverse, requestType, timeoutMs);
 	}
+
+	@Override
+	public RWScheduler getScheduler() {
+		return db.getScheduler();
+	}
 }

src/main/java/it/cavallium/rockserver/core/client/GrpcConnection.java

@@ -8,7 +8,6 @@ import com.google.common.util.concurrent.MoreExecutors;
 import com.google.protobuf.ByteString;
 import com.google.protobuf.UnsafeByteOperations;
 import io.grpc.ManagedChannel;
-import io.grpc.Status;
 import io.grpc.Status.Code;
 import io.grpc.StatusRuntimeException;
 import io.grpc.netty.NettyChannelBuilder;

src/main/java/it/cavallium/rockserver/core/common/RocksDBAPICommand.java

@@ -2,6 +2,7 @@ package it.cavallium.rockserver.core.common;
 
 import it.cavallium.rockserver.core.common.RequestType.RequestGet;
 import it.cavallium.rockserver.core.common.RequestType.RequestPut;
+import it.cavallium.rockserver.core.common.RequestType.RequestTypeId;
 import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
 import java.util.List;
@@ -18,6 +19,8 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 	SYNC_RESULT handleSync(RocksDBSyncAPI api);
 	ASYNC_RESULT handleAsync(RocksDBAsyncAPI api);
 
+	boolean isReadOnly();
+
 	sealed interface RocksDBAPICommandSingle<R> extends RocksDBAPICommand<R, R, CompletableFuture<R>> {
 
 
@@ -40,6 +43,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.openTransactionAsync(timeoutMs);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 		}
 		/**
 		 * Close a transaction
@@ -61,6 +69,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.closeTransactionAsync(transactionId, commit);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 		}
 		/**
 		 * Close a failed update, discarding all changes
@@ -80,6 +93,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.closeFailedUpdateAsync(updateId);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Create a column
@@ -101,6 +119,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.createColumnAsync(name, schema);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 		}
 		/**
 		 * Delete a column
@@ -119,6 +142,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.deleteColumnAsync(columnId);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 		}
 		/**
 		 * Get column id by name
@@ -139,6 +167,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.getColumnIdAsync(name);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Put an element into the specified position
@@ -166,6 +199,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.putAsync(arena, transactionOrUpdateId, columnId, keys, value, requestType);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 			@Override
 			public String toString() {
 				var sb = new StringBuilder("PUT");
@@ -203,6 +241,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.putMultiAsync(arena, transactionOrUpdateId, columnId, keys, values, requestType);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 			@Override
 			public String toString() {
 				var sb = new StringBuilder("PUT_MULTI");
@@ -242,6 +285,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.putBatchAsync(columnId, batchPublisher, mode);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return false;
+			}
+
 			@Override
 			public String toString() {
 				var sb = new StringBuilder("PUT_BATCH");
@@ -275,6 +323,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.getAsync(arena, transactionOrUpdateId, columnId, keys, requestType);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return requestType.getRequestTypeId() != RequestTypeId.FOR_UPDATE;
+			}
+
 			@Override
 			public String toString() {
 				var sb = new StringBuilder("GET");
@@ -325,6 +378,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Close an iterator
@@ -343,6 +401,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.closeIteratorAsync(iteratorId);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Seek to the specific element during an iteration, or the subsequent one if not found
@@ -363,6 +426,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.seekToAsync(arena, iterationId, keys);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Get the subsequent element during an iteration
@@ -389,6 +457,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				return api.subsequentAsync(arena, iterationId, skipCount, takeCount, requestType);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 		/**
 		 * Reduce values in a range
@@ -439,6 +512,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 	}
 	sealed interface RocksDBAPICommandStream<R> extends RocksDBAPICommand<R, Stream<R>, Publisher<R>> {
@@ -492,6 +570,11 @@ public sealed interface RocksDBAPICommand<RESULT_ITEM_TYPE, SYNC_RESULT, ASYNC_R
 				);
 			}
 
+			@Override
+			public boolean isReadOnly() {
+				return true;
+			}
+
 		}
 	}
 }

src/main/java/it/cavallium/rockserver/core/config/ConfigPrinter.java

@@ -28,8 +28,9 @@ public class ConfigPrinter {
 	public static String stringifyDatabase(DatabaseConfig o) throws GestaltException {
 		return """
 				{
+				  "parallelism": %s,
 				  "global": %s
-				}""".formatted(stringifyGlobalDatabase(o.global()));
+				}""".formatted(stringifyParallelism(o.parallelism()), stringifyGlobalDatabase(o.global()));
 	}
 
 	public static String stringifyLevel(ColumnLevelConfig o) throws GestaltException {
@@ -92,6 +93,17 @@ public class ConfigPrinter {
 		);
 	}
 
+	public static String stringifyParallelism(ParallelismConfig o) throws GestaltException {
+		return """
+				{
+				    "read": %d,
+				    "write": %d
+				  }\
+				""".formatted(o.read(),
+				o.write()
+		);
+	}
+
 	private static String stringifyVolume(VolumeConfig o) throws GestaltException {
 		return """
 				{

src/main/java/it/cavallium/rockserver/core/config/DatabaseConfig.java

@@ -5,4 +5,6 @@ import org.github.gestalt.config.exceptions.GestaltException;
 public interface DatabaseConfig {
 
 	GlobalDatabaseConfig global() throws GestaltException;
+
+	ParallelismConfig parallelism() throws GestaltException;
 }

src/main/java/it/cavallium/rockserver/core/config/ParallelismConfig.java

@@ -0,0 +1,16 @@
+package it.cavallium.rockserver.core.config;
+
+import java.time.Duration;
+import org.github.gestalt.config.exceptions.GestaltException;
+import org.jetbrains.annotations.Nullable;
+
+import java.nio.file.Path;
+
+public interface ParallelismConfig {
+
+	@Nullable
+	Integer read() throws GestaltException;
+
+	@Nullable
+	Integer write() throws GestaltException;
+}

src/main/java/it/cavallium/rockserver/core/impl/EmbeddedDB.java

@@ -32,6 +32,7 @@ import java.util.*;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.Executor;
 import java.util.concurrent.TimeoutException;
 import java.util.stream.Stream;
 
@@ -48,9 +49,10 @@ import org.rocksdb.Status.Code;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import reactor.core.publisher.Flux;
+import reactor.core.scheduler.Scheduler;
 import reactor.core.scheduler.Schedulers;
 
-public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
+public class EmbeddedDB implements RocksDBSyncAPI, InternalConnection, Closeable {
 
 	private static final int INITIAL_DIRECT_READ_BYTE_BUF_SIZE_BYTES = 4096;
 	public static final long MAX_TRANSACTION_DURATION_MS = 10_000L;
@@ -61,6 +63,7 @@ public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
 	private final @Nullable Path path;
 	private final TransactionalDB db;
 	private final DBOptions dbOptions;
+	private final RWScheduler scheduler;
 	private final ColumnFamilyHandle columnSchemasColumnDescriptorHandle;
 	private final NonBlockingHashMapLong<ColumnInstance> columns;
 	private final Map<String, ColumnFamilyOptions> columnsConifg;
@@ -89,6 +92,13 @@ public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
 		this.dbOptions = loadedDb.dbOptions();
 		this.refs = loadedDb.refs();
 		this.cache = loadedDb.cache();
+		try {
+			int readCap = Objects.requireNonNullElse(config.parallelism().read(), Runtime.getRuntime().availableProcessors());
+			int writeCap = Objects.requireNonNullElse(config.parallelism().write(), Runtime.getRuntime().availableProcessors());
+			this.scheduler = new RWScheduler(readCap, writeCap, "db");
+		} catch (GestaltException e) {
+			throw it.cavallium.rockserver.core.common.RocksDBException.of(RocksDBErrorType.CONFIG_ERROR, "Can't get the scheduler parallelism");
+		}
 		this.columnsConifg = loadedDb.definitiveColumnFamilyOptionsMap();
         try {
             this.tempSSTsPath = config.global().tempSstPath();
@@ -257,6 +267,12 @@ public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
 		}
 	}
 
+	private ReadOptions newReadOptions() {
+		var ro = new ReadOptions();
+		ro.setAsyncIo(true);
+		return ro;
+	}
+
 	@Override
 	public long openTransaction(long timeoutMs) {
 		return allocateTransactionInternal(openTransactionInternal(timeoutMs, false));
@@ -1157,7 +1173,7 @@ public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
 					}
 					return it;
         }), Resources::close)
-				.subscribeOn(Schedulers.boundedElastic())
+				.subscribeOn(scheduler.read())
 				.doFirst(ops::beginOp)
 				.doFinally(_ -> ops.endOp());
 	}
@@ -1270,4 +1286,9 @@ public class EmbeddedDB implements RocksDBSyncAPI, Closeable {
 		throw it.cavallium.rockserver.core.common.RocksDBException.of(RocksDBErrorType.NOT_IMPLEMENTED,
 				"Bucket column type not implemented, implement them");
 	}
+
+	@Override
+	public RWScheduler getScheduler() {
+		return scheduler;
+	}
 }

src/main/java/it/cavallium/rockserver/core/impl/InternalConnection.java

@@ -0,0 +1,6 @@
+package it.cavallium.rockserver.core.impl;
+
+public interface InternalConnection {
+
+	RWScheduler getScheduler();
+}

src/main/java/it/cavallium/rockserver/core/impl/RWScheduler.java

@@ -0,0 +1,32 @@
+package it.cavallium.rockserver.core.impl;
+
+import static reactor.core.scheduler.Schedulers.DEFAULT_BOUNDED_ELASTIC_QUEUESIZE;
+
+import java.util.concurrent.Executor;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Scheduler;
+import reactor.core.scheduler.Schedulers;
+
+public record RWScheduler(Scheduler read, Scheduler write, Executor readExecutor, Executor writeExecutor) {
+
+	public RWScheduler(Scheduler read, Scheduler write) {
+		this(read, write, read::schedule, write::schedule);
+	}
+
+	public RWScheduler(int readCap, int writeCap, String name) {
+		this(
+				Schedulers.newBoundedElastic(readCap, DEFAULT_BOUNDED_ELASTIC_QUEUESIZE, name + "-read"),
+				Schedulers.newBoundedElastic(writeCap, DEFAULT_BOUNDED_ELASTIC_QUEUESIZE, name + "-write")
+		);
+	}
+
+	public Mono<Void> disposeGracefully() {
+		return Mono.whenDelayError(read.disposeGracefully(), write.disposeGracefully());
+	}
+
+	public void dispose() {
+		read.dispose();
+		write.dispose();
+	}
+}

src/main/java/it/cavallium/rockserver/core/server/GrpcServer.java

@@ -39,6 +39,8 @@ import it.cavallium.rockserver.core.common.api.proto.*;
 import it.cavallium.rockserver.core.common.api.proto.Delta;
 import it.cavallium.rockserver.core.common.api.proto.FirstAndLast;
 import it.cavallium.rockserver.core.common.api.proto.KV;
+import it.cavallium.rockserver.core.impl.InternalConnection;
+import it.cavallium.rockserver.core.impl.RWScheduler;
 import it.unimi.dsi.fastutil.ints.Int2IntFunction;
 import it.unimi.dsi.fastutil.ints.Int2ObjectFunction;
 import it.unimi.dsi.fastutil.ints.IntArrayList;
@@ -63,8 +65,6 @@ import org.slf4j.LoggerFactory;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.FluxSink;
 import reactor.core.publisher.Mono;
-import reactor.core.scheduler.Scheduler;
-import reactor.core.scheduler.Schedulers;
 
 public class GrpcServer extends Server {
 
@@ -72,11 +72,19 @@ public class GrpcServer extends Server {
 
 	private final GrpcServerImpl grpc;
 	private final EventLoopGroup elg;
-	private final Scheduler executor;
 	private final io.grpc.Server server;
+	private final RWScheduler scheduler;
 
 	public GrpcServer(RocksDBConnection client, SocketAddress socketAddress) throws IOException {
 		super(client);
+		if (client instanceof InternalConnection internalConnection) {
+			this.scheduler = internalConnection.getScheduler();
+		} else {
+			this.scheduler = new RWScheduler(Runtime.getRuntime().availableProcessors(),
+					Runtime.getRuntime().availableProcessors(),
+					"grpc-db"
+			);
+		}
 		this.grpc = new GrpcServerImpl(this.getClient());
 		EventLoopGroup elg;
 		Class<? extends ServerChannel> channelType;
@@ -88,7 +96,6 @@ public class GrpcServer extends Server {
 			channelType = NioServerSocketChannel.class;
 		}
 		this.elg = elg;
-		this.executor = Schedulers.newBoundedElastic(Runtime.getRuntime().availableProcessors() * 2, Schedulers.DEFAULT_BOUNDED_ELASTIC_QUEUESIZE, "server-db-executor");
 		this.server = NettyServerBuilder
 				.forAddress(socketAddress)
 				.bossEventLoopGroup(elg)
@@ -125,7 +132,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				var txId = api.openTransaction(request.getTimeoutMs());
 				return OpenTransactionResponse.newBuilder().setTransactionId(txId).build();
-			}).transform(this.onErrorMapMonoWithRequestInfo("openTransaction", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("openTransaction", request));
 		}
 
 		@Override
@@ -133,7 +140,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				var committed = api.closeTransaction(request.getTransactionId(), request.getCommit());
                 return CloseTransactionResponse.newBuilder().setSuccessful(committed).build();
-			}).transform(this.onErrorMapMonoWithRequestInfo("closeTransaction", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("closeTransaction", request));
 		}
 
 		@Override
@@ -141,7 +148,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				api.closeFailedUpdate(request.getUpdateId());
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("closeFailedUpdate", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("closeFailedUpdate", request));
 		}
 
 		@Override
@@ -149,7 +156,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				var colId = api.createColumn(request.getName(), mapColumnSchema(request.getSchema()));
 				return CreateColumnResponse.newBuilder().setColumnId(colId).build();
-			}).transform(this.onErrorMapMonoWithRequestInfo("createColumn", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("createColumn", request));
 		}
 
 		@Override
@@ -157,7 +164,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				api.deleteColumn(request.getColumnId());
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("deleteColumn", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("deleteColumn", request));
 		}
 
 		@Override
@@ -165,7 +172,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				var colId = api.getColumnId(request.getName());
 				return GetColumnIdResponse.newBuilder().setColumnId(colId).build();
-			}).transform(this.onErrorMapMonoWithRequestInfo("getColumnId", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("getColumnId", request));
 		}
 
 		@Override
@@ -181,7 +188,7 @@ public class GrpcServer extends Server {
 					);
 				}
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("put", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("put", request));
 		}
 
 		@Override
@@ -233,7 +240,7 @@ public class GrpcServer extends Server {
 					var initialRequest = firstValue.getInitialRequest();
 
                     return nextRequests
-												.publishOn(executor)
+												.publishOn(scheduler.write())
 												.doOnNext(putRequest -> {
 														var data = putRequest.getData();
 														try (var arena = Arena.ofConfined()) {
@@ -272,7 +279,7 @@ public class GrpcServer extends Server {
 					}
 					return prevBuilder.build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("putGetPrevious", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("putGetPrevious", request));
 		}
 
 		@Override
@@ -295,7 +302,7 @@ public class GrpcServer extends Server {
 					}
 					return deltaBuilder.build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("putGetDelta", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("putGetDelta", request));
 		}
 
 		@Override
@@ -311,7 +318,7 @@ public class GrpcServer extends Server {
 					);
 					return Changed.newBuilder().setChanged(changed).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("putGetChanged", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("putGetChanged", request));
 		}
 
 		@Override
@@ -327,7 +334,7 @@ public class GrpcServer extends Server {
 					);
 					return PreviousPresence.newBuilder().setPresent(present).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("putGetPreviousPresence", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("putGetPreviousPresence", request));
 		}
 
 		@Override
@@ -346,7 +353,7 @@ public class GrpcServer extends Server {
 					}
 					return responseBuilder.build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("get", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("get", request));
 		}
 
 		@Override
@@ -366,7 +373,7 @@ public class GrpcServer extends Server {
 					}
 					return responseBuilder.build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("getForUpdate", request));
+			}, false).transform(this.onErrorMapMonoWithRequestInfo("getForUpdate", request));
 		}
 
 		@Override
@@ -381,7 +388,7 @@ public class GrpcServer extends Server {
 					);
 					return PreviousPresence.newBuilder().setPresent(exists).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("exists", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("exists", request));
 		}
 
 		@Override
@@ -398,7 +405,7 @@ public class GrpcServer extends Server {
 					);
 					return OpenIteratorResponse.newBuilder().setIteratorId(iteratorId).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("openIterator", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("openIterator", request));
 		}
 
 		@Override
@@ -406,7 +413,7 @@ public class GrpcServer extends Server {
 			return executeSync(() -> {
 				api.closeIterator(request.getIteratorId());
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("closeIterator", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("closeIterator", request));
 		}
 
 		@Override
@@ -416,7 +423,7 @@ public class GrpcServer extends Server {
 					api.seekTo(arena, request.getIterationId(), mapKeys(arena, request.getKeysCount(), request::getKeys));
 				}
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("seekTo", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("seekTo", request));
 		}
 
 		@Override
@@ -429,7 +436,7 @@ public class GrpcServer extends Server {
 							new RequestNothing<>());
 				}
 				return Empty.getDefaultInstance();
-			}).transform(this.onErrorMapMonoWithRequestInfo("subsequent", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("subsequent", request));
 		}
 
 		@Override
@@ -442,7 +449,7 @@ public class GrpcServer extends Server {
 							new RequestExists<>());
 					return PreviousPresence.newBuilder().setPresent(exists).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("subsequentExists", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("subsequentExists", request));
 		}
 
 		@Override
@@ -510,7 +517,7 @@ public class GrpcServer extends Server {
 					);
 					return EntriesCount.newBuilder().setCount(entriesCount).build();
 				}
-			}).transform(this.onErrorMapMonoWithRequestInfo("reduceRangeEntriesCount", request));
+			}, true).transform(this.onErrorMapMonoWithRequestInfo("reduceRangeEntriesCount", request));
 		}
 
 		@Override
@@ -533,8 +540,8 @@ public class GrpcServer extends Server {
 
 		// utils
 
-		private <T> Mono<T> executeSync(Callable<T> callable) {
+		private <T> Mono<T> executeSync(Callable<T> callable, boolean isReadOnly) {
-			return Mono.fromCallable(callable).subscribeOn(executor);
+			return Mono.fromCallable(callable).subscribeOn(isReadOnly ? scheduler.read() : scheduler.write());
 		}
 
 		// mappers
@@ -661,17 +668,12 @@ public class GrpcServer extends Server {
 			if (ex instanceof CompletionException exx) {
 				return handleError(exx.getCause());
 			} else {
-				if (ex instanceof RocksDBException e) {
+				return switch (ex) {
-					return Status.INTERNAL
+					case RocksDBException e -> Status.INTERNAL.withDescription(e.getLocalizedMessage()).withCause(e);
-							.withDescription(e.getLocalizedMessage())
+					case StatusException ex2 -> ex2.getStatus();
-							.withCause(e);
+					case StatusRuntimeException ex3 -> ex3.getStatus();
-				} else if (ex instanceof StatusException ex2) {
+					case null, default -> Status.INTERNAL.withCause(ex);
-					return ex2.getStatus();
+				};
-				} else if (ex instanceof StatusRuntimeException ex3) {
-					return ex3.getStatus();
-				} else {
-					return Status.INTERNAL.withCause(ex);
-				}
 			}
 		}
 	}
@@ -686,9 +688,9 @@ public class GrpcServer extends Server {
 			throw new RuntimeException(e);
 		}
 		elg.close();
-		executor.disposeGracefully().timeout(Duration.ofMinutes(2)).onErrorResume(ex -> {
+		scheduler.disposeGracefully().timeout(Duration.ofMinutes(2)).onErrorResume(ex -> {
 			LOG.error("Grpc server executor shutdown timed out, terminating...", ex);
-			executor.dispose();
+			scheduler.dispose();
 			return Mono.empty();
 		}).block();
 		super.close();