chore: add property for keep-transaction-alive

Adds a property to the Connection API for keeping read/write
transactions alive. This can be used in CLI-like applications
that might wait a longer period of time for user input. The
property is disabled by default, as enabling it can cause
read/write transactions to hold on to locks for a longer
period of time than intended.

Updates GoogleCloudPlatform/pgadapter#1826

google-cloud-spanner/clirr-ignored-differences.xml

@@ -732,4 +732,16 @@
     <className>com/google/cloud/spanner/connection/Connection</className>
     <method>void reset()</method>
   </difference>
+
+  <!-- Added keepTransactionAlive property -->
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/connection/Connection</className>
+    <method>void setKeepTransactionAlive(boolean)</method>
+  </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/connection/Connection</className>
+    <method>boolean isKeepTransactionAlive()</method>
+  </difference>
 </differences>

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/Connection.java

@@ -666,6 +666,25 @@ default boolean isDelayTransactionStartUntilFirstWrite() {
     throw new UnsupportedOperationException("Unimplemented");
   }
 
+  /**
+   * Sets whether this connection should keep read/write transactions alive by executing a SELECT 1
+   * once every 10 seconds during inactive read/write transactions.
+   *
+   * <p>NOTE: This will keep read/write transactions alive and hold on to locks until it is
+   * explicitly committed or rolled back.
+   */
+  default void setKeepTransactionAlive(boolean keepTransactionAlive) {
+    throw new UnsupportedOperationException("Unimplemented");
+  }
+
+  /**
+   * @return true if this connection keeps read/write transactions alive by executing a SELECT 1
+   *     once every 10 seconds during inactive read/write transactions.
+   */
+  default boolean isKeepTransactionAlive() {
+    throw new UnsupportedOperationException("Unimplemented");
+  }
+
   /**
    * Commits the current transaction of this connection. All mutations that have been buffered
    * during the current transaction will be written to the database.

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionImpl.java

@@ -220,6 +220,7 @@ static UnitOfWorkType of(TransactionMode transactionMode) {
   private boolean readOnly;
   private boolean returnCommitStats;
   private boolean delayTransactionStartUntilFirstWrite;
+  private boolean keepTransactionAlive;
 
   private UnitOfWork currentUnitOfWork = null;
   /**
@@ -439,6 +440,7 @@ public void reset() {
     this.ddlInTransactionMode = options.getDdlInTransactionMode();
     this.returnCommitStats = options.isReturnCommitStats();
     this.delayTransactionStartUntilFirstWrite = options.isDelayTransactionStartUntilFirstWrite();
+    this.keepTransactionAlive = options.isKeepTransactionAlive();
     this.dataBoostEnabled = options.isDataBoostEnabled();
     this.autoPartitionMode = options.isAutoPartitionMode();
     this.maxPartitions = options.getMaxPartitions();
@@ -988,6 +990,20 @@ public boolean isDelayTransactionStartUntilFirstWrite() {
     return this.delayTransactionStartUntilFirstWrite;
   }
 
+  @Override
+  public void setKeepTransactionAlive(boolean keepTransactionAlive) {
+    ConnectionPreconditions.checkState(!isClosed(), CLOSED_ERROR_MSG);
+    ConnectionPreconditions.checkState(
+        !isTransactionStarted(), "Cannot set KeepTransactionAlive while a transaction is active");
+    this.keepTransactionAlive = keepTransactionAlive;
+  }
+
+  @Override
+  public boolean isKeepTransactionAlive() {
+    ConnectionPreconditions.checkState(!isClosed(), CLOSED_ERROR_MSG);
+    return this.keepTransactionAlive;
+  }
+
   /** Resets this connection to its default transaction options. */
   private void setDefaultTransactionOptions() {
     if (transactionStack.isEmpty()) {
@@ -1909,6 +1925,7 @@ UnitOfWork createNewUnitOfWork(
               .setUseAutoSavepointsForEmulator(options.useAutoSavepointsForEmulator())
               .setDatabaseClient(dbClient)
               .setDelayTransactionStartUntilFirstWrite(delayTransactionStartUntilFirstWrite)
+              .setKeepTransactionAlive(keepTransactionAlive)
               .setRetryAbortsInternally(retryAbortsInternally)
               .setSavepointSupport(savepointSupport)
               .setReturnCommitStats(returnCommitStats)

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionOptions.java

@@ -192,6 +192,7 @@ public String[] getValidValues() {
   private static final boolean DEFAULT_LENIENT = false;
   private static final boolean DEFAULT_ROUTE_TO_LEADER = true;
   private static final boolean DEFAULT_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE = false;
+  private static final boolean DEFAULT_KEEP_TRANSACTION_ALIVE = false;
   private static final boolean DEFAULT_TRACK_SESSION_LEAKS = true;
   private static final boolean DEFAULT_TRACK_CONNECTION_LEAKS = true;
   private static final boolean DEFAULT_DATA_BOOST_ENABLED = false;
@@ -268,6 +269,8 @@ public String[] getValidValues() {
   /** Name of the 'delay transaction start until first write' property. */
   public static final String DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE_NAME =
       "delayTransactionStartUntilFirstWrite";
+  /** Name of the 'keep transaction alive' property. */
+  public static final String KEEP_TRANSACTION_ALIVE_PROPERTY_NAME = "keepTransactionAlive";
   /** Name of the 'trackStackTraceOfSessionCheckout' connection property. */
   public static final String TRACK_SESSION_LEAKS_PROPERTY_NAME = "trackSessionLeaks";
   /** Name of the 'trackStackTraceOfConnectionCreation' connection property. */
@@ -403,6 +406,12 @@ private static String generateGuardedConnectionPropertyError(
                           + "the first write operation in a read/write transaction will be executed using the read/write transaction. Enabling this mode can reduce locking "
                           + "and improve performance for applications that can handle the lower transaction isolation semantics.",
                       DEFAULT_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE),
+                  ConnectionProperty.createBooleanProperty(
+                      KEEP_TRANSACTION_ALIVE_PROPERTY_NAME,
+                      "Enabling this option will trigger the connection to keep read/write transactions alive by executing a SELECT 1 query once every 10 seconds "
+                          + "if no other statements are being executed. This option should be used with caution, as it can keep transactions alive and hold on to locks "
+                          + "longer than intended. This option should typically be used for CLI-type application that might wait for user input for a longer period of time.",
+                      DEFAULT_KEEP_TRANSACTION_ALIVE),
                   ConnectionProperty.createBooleanProperty(
                       TRACK_SESSION_LEAKS_PROPERTY_NAME,
                       "Capture the call stack of the thread that checked out a session of the session pool. This will "
@@ -726,6 +735,7 @@ public static Builder newBuilder() {
   private final RpcPriority rpcPriority;
   private final DdlInTransactionMode ddlInTransactionMode;
   private final boolean delayTransactionStartUntilFirstWrite;
+  private final boolean keepTransactionAlive;
   private final boolean trackSessionLeaks;
   private final boolean trackConnectionLeaks;
 
@@ -789,6 +799,7 @@ private ConnectionOptions(Builder builder) {
     this.rpcPriority = parseRPCPriority(this.uri);
     this.ddlInTransactionMode = parseDdlInTransactionMode(this.uri);
     this.delayTransactionStartUntilFirstWrite = parseDelayTransactionStartUntilFirstWrite(this.uri);
+    this.keepTransactionAlive = parseKeepTransactionAlive(this.uri);
     this.trackSessionLeaks = parseTrackSessionLeaks(this.uri);
     this.trackConnectionLeaks = parseTrackConnectionLeaks(this.uri);
 
@@ -1168,6 +1179,12 @@ static boolean parseDelayTransactionStartUntilFirstWrite(String uri) {
         : DEFAULT_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE;
   }
 
+  @VisibleForTesting
+  static boolean parseKeepTransactionAlive(String uri) {
+    String value = parseUriProperty(uri, KEEP_TRANSACTION_ALIVE_PROPERTY_NAME);
+    return value != null ? Boolean.parseBoolean(value) : DEFAULT_KEEP_TRANSACTION_ALIVE;
+  }
+
   @VisibleForTesting
   static boolean parseTrackSessionLeaks(String uri) {
     String value = parseUriProperty(uri, TRACK_SESSION_LEAKS_PROPERTY_NAME);
@@ -1298,6 +1315,14 @@ static List<String> parseProperties(String uri) {
     return res;
   }
 
+  static long tryParseLong(String value, long defaultValue) {
+    try {
+      return Long.parseLong(value);
+    } catch (NumberFormatException ignore) {
+      return defaultValue;
+    }
+  }
+
   /**
    * Create a new {@link Connection} from this {@link ConnectionOptions}. Calling this method
    * multiple times for the same {@link ConnectionOptions} will return multiple instances of {@link
@@ -1534,6 +1559,18 @@ boolean isDelayTransactionStartUntilFirstWrite() {
     return delayTransactionStartUntilFirstWrite;
   }
 
+  /**
+   * Whether connections created by this {@link ConnectionOptions} should keep read/write
+   * transactions alive by executing a SELECT 1 once every 10 seconds if no other statements are
+   * executed. This option should be used with caution, as enabling it can keep transactions alive
+   * for a very long time, which will hold on to any locks that have been taken by the transaction.
+   * This option should typically only be enabled for CLI-type applications or other user-input
+   * applications that might wait for a longer period of time on user input.
+   */
+  boolean isKeepTransactionAlive() {
+    return keepTransactionAlive;
+  }
+
   boolean isTrackConnectionLeaks() {
     return this.trackConnectionLeaks;
   }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionStatementExecutor.java

@@ -91,6 +91,10 @@ StatementResult statementSetDelayTransactionStartUntilFirstWrite(
 
   StatementResult statementShowDelayTransactionStartUntilFirstWrite();
 
+  StatementResult statementSetKeepTransactionAlive(Boolean keepTransactionAlive);
+
+  StatementResult statementShowKeepTransactionAlive();
+
   StatementResult statementSetStatementTag(String tag);
 
   StatementResult statementShowStatementTag();

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionStatementExecutorImpl.java

@@ -31,6 +31,7 @@
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_DIRECTED_READ;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_EXCLUDE_TXN_FROM_CHANGE_STREAMS;
+import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_KEEP_TRANSACTION_ALIVE;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_MAX_COMMIT_DELAY;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_MAX_PARTITIONED_PARALLELISM;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SET_MAX_PARTITIONS;
@@ -57,6 +58,7 @@
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_DIRECTED_READ;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_EXCLUDE_TXN_FROM_CHANGE_STREAMS;
+import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_KEEP_TRANSACTION_ALIVE;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_MAX_COMMIT_DELAY;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_MAX_PARTITIONED_PARALLELISM;
 import static com.google.cloud.spanner.connection.StatementResult.ClientSideStatementType.SHOW_MAX_PARTITIONS;
@@ -388,6 +390,20 @@ public StatementResult statementShowDelayTransactionStartUntilFirstWrite() {
         SHOW_DELAY_TRANSACTION_START_UNTIL_FIRST_WRITE);
   }
 
+  @Override
+  public StatementResult statementSetKeepTransactionAlive(Boolean keepTransactionAlive) {
+    getConnection().setKeepTransactionAlive(keepTransactionAlive);
+    return noResult(SET_KEEP_TRANSACTION_ALIVE);
+  }
+
+  @Override
+  public StatementResult statementShowKeepTransactionAlive() {
+    return resultSet(
+        String.format("%sKEEP_TRANSACTION_ALIVE", getNamespace(connection.getDialect())),
+        getConnection().isKeepTransactionAlive(),
+        SHOW_KEEP_TRANSACTION_ALIVE);
+  }
+
   @Override
   public StatementResult statementSetStatementTag(String tag) {
     getConnection().setStatementTag("".equals(tag) ? null : tag);