Why Am I Getting 'org.postgresql.util.PSQLException: FATAL: sorry, too many clients already' in PostgreSQL?

Understanding "org.postgresql.util.PSQLException: FATAL: sorry, too many clients already" Error

When connecting to a PostgreSQL database, encountering the error "org.postgresql.util.PSQLException: FATAL: sorry, too many clients already" indicates that the allowable limit of concurrent connections has been exceeded.

This occurs when code opens multiple connections to the database without properly closing them. While destroying and garbage collecting a class normally releases its hold on a connection, it's essential to explicitly close connections to the database.

An example of a fix is adding the following code in any class that creates a connection:

protected void finalize() throws Throwable  
{  
    try { your_connection.close(); } 
    catch (SQLException e) { 
        e.printStackTrace();
    }
    super.finalize();  
}

This ensures that the connection is released when the class is garbage collected.

It's also useful to check the maximum number of connections allowed by PostgreSQL:

show max_connections;

The default is 100. If you need more connections, you can increase this value by editing the postgresql.conf file. Search for "max_connections" and adjust it accordingly.

To determine which connections are being held open or which programs are not releasing them, you can use the following commands:

SELECT * FROM pg_stat_activity;

SELECT COUNT(*) from pg_stat_activity;

Finally, remember to track the connections that are being created and ensure they are all correctly closed.

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