Memory leak with sockets (SSLSocketImpl) in MonitoredCache

[csolem]

Bug Description

After upgrading cloud-sql-connector-jdbc-sqlserver from 1.23.1 to version 1.24.0 we have experienced several occasional memory leaks in a couple of our applications after running for a hours or even days.

InternalConnectorRegistry holds a map of unnamedConnectors. One of the entries in that map is an instance of MonitoredCache that seems to have been introduced in #2056

MonitoredCache has a field List<Socket> sockets, and when we observe the memory leak, this list has grown to a large size. In our last case, this list held 91568 instances of sun.security.ssl.SSLSocketImpl with a total memory consumption 3.7GB according to the heap dump.

https://github.com/GoogleCloudPlatform/cloud-sql-jdbc-socket-factory/blob/v1.24.0/core/src/main/java/com/google/cloud/sql/core/MonitoredCache.java#L41

Applications can run for days before this happens, We have not figured out what the trigger is. (Our applications have used the cloud-sql-connector-jdbc-sqlserver dependency for years without issues, and the memory leak did only occur after the upgrade to 1.24.0)

The screenshot below shows the relevant part from the heap dump taken from the application during the memory leak. It has been imported into Intellij for investigation, and it clearly shows the memory consumption in relation to MonitoredCache.sockets:

Relevant parts of dependency tree

[INFO] +- com.google.cloud.sql:cloud-sql-connector-jdbc-sqlserver:jar:1.24.0:compile
[INFO] |  \- com.google.cloud.sql:jdbc-socket-factory-core:jar:1.24.0:compile
[INFO] |     +- com.github.jnr:jnr-enxio:jar:0.32.18:compile
[INFO] |     \- com.google.apis:google-api-services-sqladmin:jar:v1beta4-rev20250310-2.0.0:compile
[INFO] +- com.microsoft.sqlserver:mssql-jdbc:jar:12.10.0.jre11:compile

Application runs in kubernetes on GKE with the base image eclipse-temurin:21-jre-alpine. Java application is built with jib maven plugin 3.4.4 and java compile/release version is 21. Application consumes messages from pubsub pull and writes to a mssql database using the socket factory

Example code (or command)

// JDBC url
jdbc:sqlserver://localhost;databaseName=<databaseName>;socketFactoryConstructorArg=<dbInstance>?ipTypes=PRIVATE;socketFactoryClass=com.google.cloud.sql.sqlserver.SocketFactory;trustServerCertificate=true;encrypt=true;socketTimeout=120000;queryTimeout=30;cancelQueryTimeout=20;

// Setting up data source
  public static HikariDataSource getDataSource(final ParameterResolver parameterResolver, final String databasePassword) {
    final String dbUrl = "jdbc:sqlserver://localhost;databaseName=<databaseName>;socketFactoryConstructorArg=<dbInstance>?ipTypes=PRIVATE;socketFactoryClass=com.google.cloud.sql.sqlserver.SocketFactory;trustServerCertificate=true;encrypt=true;socketTimeout=120000;queryTimeout=30;cancelQueryTimeout=20;";
    final String dbUsername = "username";
    final HikariDataSource dataSource = new HikariDataSource();
    dataSource.setDriverClassName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
    dataSource.setJdbcUrl(dbUrl);
    dataSource.setUsername(dbUsername);
    dataSource.setPassword(databasePassword);
    dataSource.setLeakDetectionThreshold(40000);
    dataSource.setKeepaliveTime(30000);
    dataSource.setMaxLifetime(60000);
    dataSource.setTransactionIsolation("TRANSACTION_READ_COMMITTED");
    final int maximumPoolSize = 20;
    dataSource.setMaximumPoolSize(maximumPoolSize);
    return dataSource;
  }

Stacktrace

Steps to reproduce?

It is hard to reproduce this memory leak issue. Will provide more information if possible.

Environment

1. OS type and version: eclipse-temurin:21-jre-alpine
2. Java SDK version: OpenJDK 64-Bit Server VM Temurin-21.0.6+7 (build 21.0.6+7-LTS, mixed mode, sharing)
3. Cloud SQL Java Socket Factory version: 1.24.0

Additional Details

No response

[jackwotherspoon]

@csolem Thanks for raising this issue, great catch!

I believe to have found the root cause and have put up a PR with the potential fix #2130

Will add some tests to verify and then will cut a release ASAP (hopefully later today) to get this resolved immediately.

Really appreciate you flagging this to us.

[hessjcg]

@csolem This will be fixed in version v1.24.1. This will be released in about an hour.

[csolem]

@hessjcg and @jackwotherspoon Thanks for fixing this so quickly!

[jackwotherspoon]

@csolem our pleasure, v1.24.1 is released 🚀 😄

Please let us know if you continue to see any issues, but this should be now fixed.

Thanks again for raising this 😄