MySQL Event Privileges

Introduction

MySQL Events are scheduled tasks that execute according to a defined timetable. However, before you can create and manage events in MySQL, you need to have the appropriate privileges. This article explores the privileges required to work with MySQL Events, how to grant these privileges, and best practices for managing event security.

Event privileges in MySQL are a critical component of database administration that controls who can create, modify, and execute scheduled tasks within your database. Understanding these privileges is essential for proper database security and functionality.

Prerequisites

Before diving into event privileges, you should have:

• A working MySQL installation (version 5.7 or later recommended)
• Basic understanding of MySQL commands and syntax
• Access to a user account with administrative privileges

Understanding MySQL Event Privileges

The EVENT Privilege

At the core of event management is the EVENT privilege. This permission allows users to:

• Create new events
• Alter existing events
• Drop (delete) events
• View events created by other users

Without this privilege, users cannot create or manage events in the MySQL database.

The SUPER Privilege (MySQL 5.7 and earlier)

In MySQL versions 5.7 and earlier, the SUPER privilege was required alongside the EVENT privilege to:

• Enable or disable the event scheduler
• Create events that run with definer privileges

The Event_Scheduler System Variable

The Event Scheduler is controlled by a system variable named event_scheduler which can be:

• ON: The scheduler is running and executes events
• OFF: The scheduler is stopped and does not execute events
• DISABLED: The scheduler is disabled and cannot be started without restarting the server

Only users with appropriate privileges can modify this system variable.

Checking and Granting Event Privileges

Checking Existing Privileges

To check if a user has event privileges:

sql

SHOW GRANTS FOR 'username'@'hostname';

Example output:

+---------------------------------------------------------------------+
| Grants for username@hostname                                         |
+---------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'username'@'hostname'                          |
| GRANT EVENT ON *.* TO 'username'@'hostname'                          |
| GRANT SELECT, INSERT, UPDATE ON `mydatabase`.* TO 'username'@'hostname' |
+---------------------------------------------------------------------+

Granting Event Privileges

To grant event privileges to a user:

sql

GRANT EVENT ON *.* TO 'username'@'hostname';

To grant event privileges only on a specific database:

sql

GRANT EVENT ON database_name.* TO 'username'@'hostname';

Revoking Event Privileges

If you need to remove event privileges from a user:

sql

REVOKE EVENT ON *.* FROM 'username'@'hostname';

Checking the Event Scheduler Status

To check if the Event Scheduler is running:

sql

SHOW VARIABLES LIKE 'event_scheduler';

Example output:

+----------------+-------+
| Variable_name  | Value |
+----------------+-------+
| event_scheduler | ON    |
+----------------+-------+

Enabling the Event Scheduler

To enable the Event Scheduler (requires privileges):

sql

SET GLOBAL event_scheduler = ON;

Alternatively, you can enable it in the MySQL configuration file (my.cnf or my.ini):

[mysqld]
event_scheduler=ON

Practical Examples

Example 1: Creating a User with Event Privileges

Let's create a dedicated user for managing database maintenance events:

sql

-- Create new user
CREATE USER 'maintenance_user'@'localhost' IDENTIFIED BY 'secure_password';

-- Grant necessary privileges
GRANT EVENT ON *.* TO 'maintenance_user'@'localhost';
GRANT SELECT, INSERT, UPDATE, DELETE ON maintenance_db.* TO 'maintenance_user'@'localhost';

-- Verify the privileges
SHOW GRANTS FOR 'maintenance_user'@'localhost';

Example 2: Creating an Event with the New User

After logging in as maintenance_user:

sql

-- First, select the database to use
USE maintenance_db;

-- Create an event to delete old logs every week
DELIMITER //
CREATE EVENT cleanup_old_logs
ON SCHEDULE EVERY 1 WEEK
STARTS CURRENT_TIMESTAMP
DO
BEGIN
    DELETE FROM system_logs WHERE log_date < DATE_SUB(NOW(), INTERVAL 3 MONTH);
    INSERT INTO maintenance_log (action, execution_time) VALUES ('Old logs cleanup', NOW());
END //
DELIMITER ;

Example 3: Managing Events

Once you have the appropriate privileges, you can manage events with:

sql

-- List all events in the current database
SHOW EVENTS;

-- List events in a specific database
SHOW EVENTS FROM database_name;

-- Disable a specific event
ALTER EVENT cleanup_old_logs DISABLE;

-- Enable a specific event
ALTER EVENT cleanup_old_logs ENABLE;

-- Delete an event
DROP EVENT cleanup_old_logs;

Definer vs Invoker Security Context

MySQL events run with the privileges of their definer, not the current user. This is an important security concept to understand.

Understanding DEFINER

When you create an event, the DEFINER clause specifies which user's privileges the event will use when it executes:

sql

CREATE DEFINER = 'admin'@'localhost' EVENT my_event
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY
DO
    UPDATE accounts SET status = 'inactive' WHERE last_login < DATE_SUB(NOW(), INTERVAL 1 YEAR);

This event will execute with admin@localhost privileges, regardless of which user enabled the event scheduler.

If omitted, the current user becomes the definer.

Best Practices for Event Privileges

1. Follow the principle of least privilege:

   • Grant only the specific privileges needed for each user
   • Consider creating dedicated event users with limited permissions

2. Use database-specific privileges:

   • Instead of granting EVENT on *.*, prefer granting on specific databases

3. Regularly audit event privileges:

   sql

   SELECT User, Host 
   FROM mysql.user 
   WHERE Event_priv = 'Y';

4. Document all scheduled events:

   • Keep a record of all events, their purpose, schedule, and owner
   • Review and clean up unused events regularly

5. Monitor event execution:

   • Create a logging system for event execution
   • Check the MySQL error log for event-related issues

Troubleshooting Common Privilege Issues

"Access Denied" Error When Creating Events

If you encounter this error:

ERROR 1227 (42000): Access denied; you need (at least one of) the EVENT privilege(s) for this operation

Solution:

sql

-- Grant the EVENT privilege
GRANT EVENT ON database_name.* TO 'username'@'hostname';

Event Created But Not Running

Possible causes and solutions:

1. Event scheduler is OFF:

   sql

   SET GLOBAL event_scheduler = ON;

2. Event is disabled:

   sql

   ALTER EVENT event_name ENABLE;

3. Definer lacks privileges for the event actions:

   sql

   -- Grant the necessary privileges to the definer
   GRANT SELECT, UPDATE ON database_name.* TO 'definer'@'hostname';

Implementing Event Privilege Auditing

A good practice is to implement regular auditing of event privileges. Here's a simple script to help:

sql

-- Create an event privilege audit table
CREATE TABLE event_privilege_audit (
    audit_id INT AUTO_INCREMENT PRIMARY KEY,
    audit_date DATETIME DEFAULT CURRENT_TIMESTAMP,
    username VARCHAR(255),
    hostname VARCHAR(255),
    has_event_priv ENUM('Y','N'),
    has_super_priv ENUM('Y','N')
);

-- Create an event to run the audit weekly
DELIMITER //
CREATE EVENT audit_event_privileges
ON SCHEDULE EVERY 1 WEEK
DO
BEGIN
    INSERT INTO event_privilege_audit (username, hostname, has_event_priv, has_super_priv)
    SELECT User, Host, Event_priv, Super_priv
    FROM mysql.user
    WHERE Event_priv = 'Y' OR Super_priv = 'Y';
END //
DELIMITER ;

Summary

MySQL Event privileges are essential for properly managing scheduled tasks within your database. The key points to remember are:

• The EVENT privilege is required for creating and managing events
• Events run with the security context of their definer
• Always follow the principle of least privilege when granting event permissions
• Regularly audit who has event privileges in your database
• The Event Scheduler must be enabled for events to execute

By understanding and properly managing event privileges, you can ensure your scheduled database tasks run securely and efficiently while maintaining proper access controls.

Further Resources

• MySQL Official Documentation on Privileges
• MySQL Event Scheduler Reference
• MySQL Security Best Practices

Practice Exercises

1. Create a new user with limited privileges and grant them event permissions on a single database.
2. Create an event that performs a simple maintenance task, like deleting old records.
3. Implement an audit event that tracks changes to important tables.
4. Write a script that lists all events along with their definers to audit who owns which scheduled tasks.
5. Configure the Event Scheduler in a my.cnf file and restart the MySQL server to test the configuration.