How to diagnose and fix the 25P03 idle_in_transaction_session_timeout error code in Postgres.

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The 25P03 error code in PostgreSQL corresponds to idle_in_transaction_session_timeout, which signifies that a session has been terminated because it was idle in a transaction for longer than the idle_in_transaction_session_timeout setting. This setting is a part of PostgreSQL’s configuration that helps to avoid issues with long-running transactions holding locks for more time than necessary, which can lead to contention and performance problems.

When a session exceeds the specified timeout while idle in a transaction, PostgreSQL will terminate the session to release the held resources. Here are some scenarios where this might happen, along with explanations and solutions:

Example 1: Long-Running Transaction Exceeding the Timeout

If you start a transaction and then don’t perform any operations for a period longer than the idle_in_transaction_session_timeout, the session will be terminated.

-- Start a transaction
BEGIN;
-- Execute some SQL command
UPDATE accounts SET balance = balance - 100.00 WHERE account_id = 1;

-- If you now wait without issuing a COMMIT/ROLLBACK longer than the timeout,
-- the session will be terminated with the 25P03 error.

Diagnosis:

Check for long-running transactions in your application logs or by querying the pg_stat_activity system view.

Fix:

Ensure that transactions are completed (either committed or rolled back) promptly:

-- Start a transaction
BEGIN;
-- Execute some SQL command
UPDATE accounts SET balance = balance - 100.00 WHERE account_id = 1;
-- Complete the transaction
COMMIT;

Example 2: Forgotten Transaction in Application Code

Sometimes, an application might start a transaction and then due to a bug or logic error, fail to commit or roll back, leaving the transaction open and idle.

Diagnosis:

Review application code to find where transactions are started and ensure they are always properly closed. Also, look for error handling that might inadvertently leave a transaction open.

Fix:

Implement proper error handling and ensure that all transactions are closed. For example, in pseudocode:

beginTransaction();
try {
    performDatabaseOperations();
    commitTransaction();
} catch (Exception e) {
    rollbackTransaction();
    logError(e);
}

Example 3: Unintentionally Long Idle Times in Interactive Sessions

During an interactive database session, such as with psql or another database tool, you might start a transaction and then get distracted, leaving the transaction idle.

Diagnosis:

Monitor your interactive sessions to ensure you don’t leave transactions open without activity.

Fix:

Make it a habit to either commit or roll back transactions as soon as your work is complete. If you know you will be away, you can set a reminder or use tool-specific features to alert you to open transactions.

Example 4: Misconfigured idle_in_transaction_session_timeout

The idle_in_transaction_session_timeout setting might be configured too low for your application’s workflow, leading to premature session terminations.

Diagnosis:

Check the current setting of idle_in_transaction_session_timeout in the PostgreSQL configuration file or by running:

SHOW idle_in_transaction_session_timeout;

Fix:

Adjust the idle_in_transaction_session_timeout setting in the postgresql.conf file to a value that better suits your application’s needs, and then reload the PostgreSQL configuration:

-- To change the setting for the current session
SET idle_in_transaction_session_timeout = '15min';
-- Or change in the postgresql.conf file for a permanent adjustment

Remember to reload the configuration after making changes:

SELECT pg_reload_conf();

In summary, to diagnose and fix the 25P03 error, you should:

  1. Ensure that your application logic properly closes transactions.
  2. Adjust the idle_in_transaction_session_timeout setting if necessary.
  3. Monitor both application and interactive sessions to avoid leaving transactions open without activity.
  4. Consider implementing application-side or database-side monitoring to alert on long-running transactions.

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