Add beginReadOnly() method to transaction abstraction

core/src/integration-test/java/com/scalar/db/transaction/jdbc/JdbcTransactionIntegrationTest.java

@@ -7,6 +7,8 @@
 import java.util.Properties;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 
 public class JdbcTransactionIntegrationTest extends DistributedTransactionIntegrationTestBase {
 
@@ -42,4 +44,16 @@ public void abort_forOngoingTransaction_ShouldAbortCorrectly() {}
   @Override
   @Test
   public void rollback_forOngoingTransaction_ShouldRollbackCorrectly() {}
+
+  @Disabled("Implement later")
+  @Override
+  @Test
+  public void get_GetGivenForCommittedRecord_InReadOnlyMode_ShouldReturnRecord() {}
+
+  @Disabled("Implement later")
+  @Override
+  @ParameterizedTest
+  @EnumSource(ScanType.class)
+  public void scanOrGetScanner_ScanGivenForCommittedRecord_InReadOnlyMode_ShouldReturnRecords(
+      ScanType scanType) {}
 }

core/src/main/java/com/scalar/db/api/DistributedTransactionManager.java

@@ -81,6 +81,34 @@ public interface DistributedTransactionManager
   DistributedTransaction begin(String txId)
       throws TransactionNotFoundException, TransactionException;
 
+  /**
+   * Begins a new transaction in read-only mode.
+   *
+   * @return {@link DistributedTransaction}
+   * @throws TransactionNotFoundException if the transaction fails to begin due to transient faults.
+   *     You can retry the transaction
+   * @throws TransactionException if the transaction fails to begin due to transient or nontransient
+   *     faults. You can try retrying the transaction, but you may not be able to begin the
+   *     transaction due to nontransient faults
+   */
+  DistributedTransaction beginReadOnly() throws TransactionNotFoundException, TransactionException;
+
+  /**
+   * Begins a new transaction with the specified transaction ID in read-only mode. It is users'
+   * responsibility to guarantee uniqueness of the ID, so it is not recommended to use this method
+   * unless you know exactly what you are doing.
+   *
+   * @param txId an user-provided unique transaction ID
+   * @return {@link DistributedTransaction}
+   * @throws TransactionNotFoundException if the transaction fails to begin due to transient faults.
+   *     You can retry the transaction
+   * @throws TransactionException if the transaction fails to begin due to transient or nontransient
+   *     faults. You can try retrying the transaction, but you may not be able to begin the
+   *     transaction due to nontransient faults
+   */
+  DistributedTransaction beginReadOnly(String txId)
+      throws TransactionNotFoundException, TransactionException;
+
   /**
    * Starts a new transaction. This method is an alias of {@link #begin()}.
    *
@@ -112,6 +140,39 @@ default DistributedTransaction start(String txId)
     return begin(txId);
   }
 
+  /**
+   * Starts a new transaction in read-only mode. This method is an alias of {@link
+   * #beginReadOnly()}.
+   *
+   * @return {@link DistributedTransaction}
+   * @throws TransactionNotFoundException if the transaction fails to start due to transient faults.
+   *     You can retry the transaction
+   * @throws TransactionException if the transaction fails to start due to transient or nontransient
+   *     faults. You can try retrying the transaction, but you may not be able to start the
+   *     transaction due to nontransient faults
+   */
+  default DistributedTransaction startReadOnly()
+      throws TransactionNotFoundException, TransactionException {
+    return beginReadOnly();
+  }
+
+  /**
+   * Starts a new transaction with the specified transaction ID in read-only mode. This method is an
+   * alias of {@link #beginReadOnly(String)}.
+   *
+   * @param txId an user-provided unique transaction ID
+   * @return {@link DistributedTransaction}
+   * @throws TransactionNotFoundException if the transaction fails to start due to transient faults.
+   *     You can retry the transaction
+   * @throws TransactionException if the transaction fails to start due to transient or nontransient
+   *     faults. You can try retrying the transaction, but you may not be able to start the
+   *     transaction due to nontransient faults
+   */
+  default DistributedTransaction startReadOnly(String txId)
+      throws TransactionNotFoundException, TransactionException {
+    return beginReadOnly(txId);
+  }
+
   /**
    * Starts a new transaction with the specified {@link Isolation} level.
    *

core/src/main/java/com/scalar/db/common/ActiveTransactionManagedDistributedTransactionManager.java

@@ -26,9 +26,11 @@
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.BiConsumer;
+import javax.annotation.concurrent.ThreadSafe;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@ThreadSafe
 public class ActiveTransactionManagedDistributedTransactionManager
     extends DecoratedDistributedTransactionManager {
 

core/src/main/java/com/scalar/db/common/ActiveTransactionManagedTwoPhaseCommitTransactionManager.java

@@ -28,9 +28,11 @@
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.BiConsumer;
+import javax.annotation.concurrent.ThreadSafe;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@ThreadSafe
 public class ActiveTransactionManagedTwoPhaseCommitTransactionManager
     extends DecoratedTwoPhaseCommitTransactionManager {
 

core/src/main/java/com/scalar/db/common/DecoratedDistributedTransactionManager.java

@@ -76,6 +76,16 @@ public DistributedTransaction begin(String txId) throws TransactionException {
     return decorateTransactionOnBeginOrStart(transactionManager.begin(txId));
   }
 
+  @Override
+  public DistributedTransaction beginReadOnly() throws TransactionException {
+    return decorateTransactionOnBeginOrStart(transactionManager.beginReadOnly());
+  }
+
+  @Override
+  public DistributedTransaction beginReadOnly(String txId) throws TransactionException {
+    return decorateTransactionOnBeginOrStart(transactionManager.beginReadOnly(txId));
+  }
+
   @Override
   public DistributedTransaction start() throws TransactionException {
     return decorateTransactionOnBeginOrStart(transactionManager.start());
@@ -86,6 +96,16 @@ public DistributedTransaction start(String txId) throws TransactionException {
     return decorateTransactionOnBeginOrStart(transactionManager.start(txId));
   }
 
+  @Override
+  public DistributedTransaction startReadOnly(String txId) throws TransactionException {
+    return decorateTransactionOnBeginOrStart(transactionManager.startReadOnly(txId));
+  }
+
+  @Override
+  public DistributedTransaction startReadOnly() throws TransactionException {
+    return decorateTransactionOnBeginOrStart(transactionManager.startReadOnly());
+  }
+
   /** @deprecated As of release 2.4.0. Will be removed in release 4.0.0. */
   @Deprecated
   @Override

core/src/main/java/com/scalar/db/common/ReadOnlyDistributedTransaction.java

@@ -0,0 +1,75 @@
+package com.scalar.db.common;
+
+import com.scalar.db.api.Delete;
+import com.scalar.db.api.DistributedTransaction;
+import com.scalar.db.api.Insert;
+import com.scalar.db.api.Mutation;
+import com.scalar.db.api.Put;
+import com.scalar.db.api.Update;
+import com.scalar.db.api.Upsert;
+import com.scalar.db.common.error.CoreError;
+import com.scalar.db.exception.transaction.CrudException;
+import java.util.List;
+import javax.annotation.concurrent.NotThreadSafe;
+
+@NotThreadSafe
+public class ReadOnlyDistributedTransaction extends DecoratedDistributedTransaction {
+
+  public ReadOnlyDistributedTransaction(DistributedTransaction transaction) {
+    super(transaction);
+  }
+
+  /** @deprecated As of release 3.13.0. Will be removed in release 5.0.0. */
+  @Deprecated
+  @Override
+  public void put(Put put) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  /** @deprecated As of release 3.13.0. Will be removed in release 5.0.0. */
+  @Deprecated
+  @Override
+  public void put(List<Put> puts) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  @Override
+  public void insert(Insert insert) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  @Override
+  public void upsert(Upsert upsert) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  @Override
+  public void update(Update update) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  @Override
+  public void delete(Delete delete) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  /** @deprecated As of release 3.13.0. Will be removed in release 5.0.0. */
+  @Deprecated
+  @Override
+  public void delete(List<Delete> deletes) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+
+  @Override
+  public void mutate(List<? extends Mutation> mutations) throws CrudException {
+    throw new IllegalStateException(
+        CoreError.MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION.buildMessage(getId()));
+  }
+}

core/src/main/java/com/scalar/db/common/StateManagedDistributedTransactionManager.java

@@ -20,7 +20,9 @@
 import com.scalar.db.exception.transaction.UnknownTransactionStatusException;
 import java.util.List;
 import java.util.Optional;
+import javax.annotation.concurrent.ThreadSafe;
 
+@ThreadSafe
 public class StateManagedDistributedTransactionManager
     extends DecoratedDistributedTransactionManager {
 

core/src/main/java/com/scalar/db/common/StateManagedTwoPhaseCommitTransactionManager.java

@@ -22,7 +22,9 @@
 import com.scalar.db.exception.transaction.ValidationException;
 import java.util.List;
 import java.util.Optional;
+import javax.annotation.concurrent.ThreadSafe;
 
+@ThreadSafe
 public class StateManagedTwoPhaseCommitTransactionManager
     extends DecoratedTwoPhaseCommitTransactionManager {
 

core/src/main/java/com/scalar/db/common/error/CoreError.java

@@ -923,6 +923,12 @@ public enum CoreError implements ScalarDbError {
       "Some scanners were not closed. All scanners must be closed before preparing the transaction.",
       "",
       ""),
+  MUTATION_NOT_ALLOWED_IN_READ_ONLY_TRANSACTION(
+      Category.USER_ERROR,
+      "0207",
+      "Mutations are not allowed in read-only transactions. Transaction ID: %s",
+      "",
+      ""),
 
   //
   // Errors for the concurrency error category

core/src/main/java/com/scalar/db/service/TransactionService.java

@@ -81,6 +81,16 @@ public DistributedTransaction begin(String txId) throws TransactionException {
     return manager.begin(txId);
   }
 
+  @Override
+  public DistributedTransaction beginReadOnly() throws TransactionException {
+    return manager.beginReadOnly();
+  }
+
+  @Override
+  public DistributedTransaction beginReadOnly(String txId) throws TransactionException {
+    return manager.beginReadOnly(txId);
+  }
+
   @Override
   public DistributedTransaction start() throws TransactionException {
     return manager.start();
@@ -91,6 +101,16 @@ public DistributedTransaction start(String txId) throws TransactionException {
     return manager.start(txId);
   }
 
+  @Override
+  public DistributedTransaction startReadOnly() throws TransactionException {
+    return manager.startReadOnly();
+  }
+
+  @Override
+  public DistributedTransaction startReadOnly(String txId) throws TransactionException {
+    return manager.startReadOnly(txId);
+  }
+
   /** @deprecated As of release 2.4.0. Will be removed in release 4.0.0. */
   @Deprecated
   @Override

core/src/main/java/com/scalar/db/transaction/consensuscommit/ConsensusCommitManager.java

@@ -145,6 +145,16 @@ public DistributedTransaction begin(String txId) {
     return begin(txId, config.getIsolation());
   }
 
+  @Override
+  public DistributedTransaction beginReadOnly() {
+    throw new UnsupportedOperationException("implement later");
+  }
+
+  @Override
+  public DistributedTransaction beginReadOnly(String txId) {
+    throw new UnsupportedOperationException("implement later");
+  }
+
   /** @deprecated As of release 2.4.0. Will be removed in release 4.0.0. */
   @Deprecated
   @Override

core/src/main/java/com/scalar/db/transaction/jdbc/JdbcTransactionManager.java

@@ -109,6 +109,16 @@ public DistributedTransaction begin(String txId) throws TransactionException {
     }
   }
 
+  @Override
+  public DistributedTransaction beginReadOnly() {
+    throw new UnsupportedOperationException("implement later");
+  }
+
+  @Override
+  public DistributedTransaction beginReadOnly(String txId) {
+    throw new UnsupportedOperationException("implement later");
+  }
+
   /** @deprecated As of release 2.4.0. Will be removed in release 4.0.0. */
   @SuppressWarnings("InlineMeSuggester")
   @Deprecated

core/src/main/java/com/scalar/db/transaction/singlecrudoperation/SingleCrudOperationTransactionManager.java

@@ -76,6 +76,20 @@ public DistributedTransaction begin(String txId) throws TransactionException {
             .buildMessage());
   }
 
+  @Override
+  public DistributedTransaction beginReadOnly() throws TransactionException {
+    throw new UnsupportedOperationException(
+        CoreError.SINGLE_CRUD_OPERATION_TRANSACTION_BEGINNING_TRANSACTION_NOT_ALLOWED
+            .buildMessage());
+  }
+
+  @Override
+  public DistributedTransaction beginReadOnly(String txId) throws TransactionException {
+    throw new UnsupportedOperationException(
+        CoreError.SINGLE_CRUD_OPERATION_TRANSACTION_BEGINNING_TRANSACTION_NOT_ALLOWED
+            .buildMessage());
+  }
+
   /** @deprecated As of release 2.4.0. Will be removed in release 4.0.0. */
   @Deprecated
   @Override