Why Am I Getting a 'Too Many Clients' Error When Connecting to PostgreSQL?

Too Many Clients: Troubleshooting Postgresql Connection Errors

When attempting to connect to a PostgreSQL database, you may encounter the error:

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

Error Explanation:

This error occurs when the maximum number of simultaneous connections to the database has been exceeded. PostgreSQL has a default limit of 100 connections, which can be adjusted in the postgresql.conf file.

Cause of Error:

The most likely cause of this error is that your code has opened and not closed database connections properly. Even after your class is destroyed and garbage collected, it may not release the connection to the database.

Resolution:

To resolve this error, you need to ensure that all connections are closed after use. This can be done by adding the following code to any class that creates a connection:

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

This code will close the connection when your class is garbage collected.

Additional Troubleshooting:

• Run the following SQL command to check the maximum connections allowed:

  show max_connections;

• Check the current number of connections:

  SELECT COUNT(*) from pg_stat_activity;

• Use SELECT * FROM pg_stat_activity; to identify which processes are holding open connections.

Setting Max Connections:

If necessary, you can increase the maximum number of connections allowed in the postgresql.conf file. Search for the line max_connections=100, and change the value to a higher number.

Maximum Max Connections:

The theoretical maximum number of connections is 8,388,607. However, it is not recommended to set max_connections too high, as this can lead to resource exhaustion and performance issues. A sensible value for max_connections is typically around 100.

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