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GH-932: [JDBC] Fix memory leak on Connection#close due to unclosed Statement(s) #933

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GH-932: [JDBC] Fix memory leak on Connection#close due to unclosed Statement(s) #933

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3c2c004
Fix memory leak
ennuite Dec 7, 2025
2018ac0
Add test
ennuite Dec 14, 2025
87ee7bf
Refactor ArrowFlightConnection.close()
ennuite Dec 14, 2025
5eb9998
Simplify Connection.close() logic
ennuite Dec 14, 2025
08186a8
Refactor: Ensure all resources are closed when exceptions are thrown
ennuite Jan 8, 2026
520d980
Updated branch from upstream
ennuite Jan 8, 2026
6c81ae0
Refactor: Fix formatting
ennuite Jan 8, 2026
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39 changes: 30 additions & 9 deletions ...light-sql-jdbc-core/src/main/java/org/apache/arrow/driver/jdbc/ArrowFlightConnection.java
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@lidavidm lidavidm Dec 14, 2025

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Yeah, I think it would be great to just build up a single list of AutoCloseables that we can pass to AutoCloseables so that an exception in one doesn't skip the rest, and hopefully that will clean up the logic too.

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@ennuite ennuite Jan 8, 2026 •
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I can't build a single list of AutoCloseables because ExecutorService isn't AutoCloseable before Java 19. I built a list with the ones I could, and left the try catch logic for the rest. Is this ok?

A question that hit me while doing this was what MT-safety guarantees we have on the implementation of the JDBC driver. The JDBC 4.3 spec doesn't speak about whether implementations of interfaces such as Connection need to be MT-safe, but older versions of the spec do speak about it: https://web.archive.org/web/20090213013250/http://java.sun.com/j2se/1.3/docs/guide/jdbc/spec/jdbc-spec.frame9.html

It seems to me like we are assuming each Connection is only used in a single thread, is this documented somewhere?

Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@

import io.netty.util.concurrent.DefaultThreadFactory;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Properties;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
Expand Down Expand Up @@ -180,19 +181,39 @@ public Properties getClientInfo() {

@Override
public void close() throws SQLException {
clientHandler.close();
if (executorService != null) {
executorService.shutdown();
Exception topLevelException = null;
try {
if (executorService != null) {
executorService.shutdown();
}
} catch (final Exception e) {
topLevelException = e;
}
ArrayList<AutoCloseable> closeables = new ArrayList<>(statementMap.values());
closeables.add(clientHandler);
closeables.addAll(allocator.getChildAllocators());
closeables.add(allocator);
try {
AutoCloseables.close(closeables);
} catch (final Exception e) {
if (topLevelException == null) {
topLevelException = e;
} else {
topLevelException.addSuppressed(e);
}
}

try {
AutoCloseables.close(clientHandler);
allocator.getChildAllocators().forEach(AutoCloseables::closeNoChecked);
AutoCloseables.close(allocator);

super.close();
} catch (final Exception e) {
throw AvaticaConnection.HELPER.createException(e.getMessage(), e);
if (topLevelException == null) {
topLevelException = e;
} else {
topLevelException.addSuppressed(e);
}
}
if (topLevelException != null) {
throw AvaticaConnection.HELPER.createException(
topLevelException.getMessage(), topLevelException);
}
}

Expand Down
38 changes: 38 additions & 0 deletions flight/flight-sql-jdbc-core/src/test/java/org/apache/arrow/driver/jdbc/ConnectionTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
package org.apache.arrow.driver.jdbc;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
Expand All @@ -27,6 +28,7 @@
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Map;
import java.util.Properties;
import org.apache.arrow.driver.jdbc.authentication.UserPasswordAuthentication;
Expand Down Expand Up @@ -660,4 +662,40 @@ public String visit(String value) {
assertEquals(catalog, actualCatalog);
}
}

@Test
public void testStatementsClosedOnConnectionClose() throws Exception {
// create a connection
final Properties properties = new Properties();
properties.put(ArrowFlightConnectionProperty.HOST.camelName(), "localhost");
properties.put(
ArrowFlightConnectionProperty.PORT.camelName(), FLIGHT_SERVER_TEST_EXTENSION.getPort());
properties.put(ArrowFlightConnectionProperty.USER.camelName(), userTest);
properties.put(ArrowFlightConnectionProperty.PASSWORD.camelName(), passTest);
properties.put("useEncryption", false);

Connection connection =
DriverManager.getConnection(
"jdbc:arrow-flight-sql://"
+ FLIGHT_SERVER_TEST_EXTENSION.getHost()
+ ":"
+ FLIGHT_SERVER_TEST_EXTENSION.getPort(),
properties);

// create some statements
int numStatements = 3;
Statement[] statements = new Statement[numStatements];
for (int i = 0; i < numStatements; i++) {
statements[i] = connection.createStatement();
assertFalse(statements[i].isClosed());
}

// close the connection
connection.close();

// assert the statements are closed
for (int i = 0; i < numStatements; i++) {
assertTrue(statements[i].isClosed());
}
}
}