Scheduled shutdowns

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  1. Scheduled Shutdowns

Scheduled Shutdowns are a critical, yet often overlooked, aspect of maintaining a robust and reliable MediaWiki installation. They represent periods of planned downtime, essential for performing maintenance tasks that cannot be safely or effectively carried out while the wiki is live and serving users. This article provides a comprehensive guide to understanding, planning, and executing scheduled shutdowns, aimed at wiki administrators and those involved in maintaining a MediaWiki site.

Why are Scheduled Shutdowns Necessary?

While the goal is to provide continuous uptime, some maintenance tasks inherently require the wiki to be offline. These tasks fall into several categories:

  • Software Upgrades: Upgrading MediaWiki core, extensions, or the underlying server software (PHP, MySQL/MariaDB, web server) often necessitate downtime. Upgrades frequently involve database schema changes or code modifications that are incompatible with a live system. A rollback plan is vital during these upgrades, and a downtime period ensures clean execution.
  • Database Maintenance: Databases require regular maintenance to optimize performance and prevent corruption. Tasks like optimizing tables, rebuilding indexes, and running consistency checks are best performed during periods of low or no activity. Large wikis, particularly those with extensive histories, benefit greatly from regular database optimization. Ignoring this can lead to significant performance degradation over time.
  • Server Hardware Maintenance: Physical server hardware requires periodic maintenance, including firmware updates, hardware replacements (e.g., RAM, hard drives), and preventative maintenance. These tasks generally require a server reboot, making downtime unavoidable.
  • Configuration Changes: Significant changes to the wiki’s configuration, such as altering the database connection settings, adjusting PHP memory limits, or modifying the web server configuration, may require a restart of services.
  • Extension Installation/Removal: Installing or removing complex extensions can sometimes necessitate downtime, especially if they involve database schema changes or significant code integration.
  • Large-Scale Data Imports/Exports: Importing or exporting large datasets (e.g., migrating data from another wiki) can place a significant load on the server. Performing these operations during scheduled downtime minimizes the impact on active users.
  • Security Patches: Applying critical security patches may require a restart of services to ensure the changes are fully implemented. Prompt application of security patches is crucial, even if it necessitates downtime.
  • Backups: While ideally backups should be performed without interrupting service (using techniques like snapshotting), some backup methods, particularly full database backups on very large databases, can significantly impact performance and are best scheduled during downtime.

Planning a Scheduled Shutdown

Effective planning is paramount to minimize disruption and ensure a smooth shutdown and restart process.

1. Define the Scope: Clearly identify *what* will be done during the shutdown. A detailed list of tasks is essential. This list should include estimated completion times for each task. Consider dependencies between tasks; some tasks may need to be completed before others can begin. 2. Determine the Duration: Estimate the total downtime required. Be realistic and add a buffer for unexpected issues. It's better to overestimate and finish early than to underestimate and extend the downtime. Factor in time for verification and testing after the maintenance is complete. 3. Choose the Best Time: This is arguably the most important aspect of planning. Consider your wiki’s user base and their geographical distribution. Identify periods of low activity. Tools like Wikimedia Traffic Analysis (though focused on Wikimedia projects, the principles are applicable) can provide insights into traffic patterns. Weekends and late-night hours (relative to your primary user base) are often good choices. Avoid scheduling shutdowns during major events or announcements that are likely to drive traffic to the wiki. 4. Communication is Key: Notify your users *well in advance* of the scheduled shutdown. Utilize all available communication channels:

   * Wiki Announcements:  Place a prominent announcement on the wiki's main page, as well as relevant project pages.  Use a template (e.g., Template:ShutdownNotice) for consistency.
   * Email Notifications:  If you have a user mailing list, send an email notification.
   * Social Media:  Post announcements on any social media platforms your wiki uses.
   * Status Page: Consider using a dedicated status page (e.g., using services like Statuspage.io) to provide real-time updates on the shutdown progress.

5. Create a Checklist: Develop a detailed checklist of tasks to be performed *before*, *during*, and *after* the shutdown. This checklist should include:

   * Pre-Shutdown Tasks:
       *  Full backup of the wiki files and database.  Verify the backup's integrity.
       *  Stop any scheduled tasks (cron jobs) that might interfere with the maintenance.
       *  Put the wiki into maintenance mode (see below).
       *  Record current server resource usage (CPU, memory, disk I/O).
   * Shutdown Tasks:
       *  Perform the planned maintenance tasks (software upgrades, database optimization, etc.).
       *  Monitor server logs for errors.
   * Post-Shutdown Tasks:
       *  Restart all necessary services (web server, database server, MediaWiki).
       *  Clear any caches (e.g., MediaWiki’s object cache, the web server cache).
       *  Run a smoke test to verify basic functionality (e.g., can you view the main page, can you edit a page, can you search).
       *  Monitor server resource usage to ensure performance is as expected.
       *  Remove the wiki from maintenance mode.
       *  Resume any previously stopped scheduled tasks.
       *  Announce the wiki is back online.

6. Rollback Plan: Develop a detailed rollback plan in case something goes wrong during the shutdown. This plan should outline the steps to restore the wiki to its previous state. Having a recent, verified backup is crucial for a successful rollback. Test the rollback procedure periodically to ensure it works. 7. Assign Responsibilities: Clearly assign responsibility for each task to specific individuals. Ensure everyone involved understands their roles and responsibilities. 8. Documentation: Document the entire shutdown process, including the scope, duration, checklist, rollback plan, and any issues encountered. This documentation will be invaluable for future shutdowns.

Putting the Wiki into Maintenance Mode

MediaWiki provides a built-in maintenance mode that displays a customizable message to users while the wiki is offline for maintenance. This is activated by creating a file named `maintenance/maintenance.php` in the root directory of your MediaWiki installation.

The contents of this file should be:

```php <?php

 require_once( 'includes/web/maintenance/maintenance.php' );

?> ```

When this file exists, any request to the wiki will display the maintenance message instead of the normal wiki content. The message can be customized by editing the `includes/web/maintenance/MaintenancePage.php` file.

Remember to *remove* the `maintenance/maintenance.php` file after the shutdown is complete to restore normal wiki functionality. Failing to remove this file will keep the wiki in maintenance mode indefinitely!

Monitoring and Troubleshooting

During the shutdown, actively monitor the server and the maintenance process.

  • Server Logs: Check the web server logs (e.g., Apache or Nginx) and the database server logs for any errors.
  • Resource Usage: Monitor CPU usage, memory usage, and disk I/O to identify any performance bottlenecks.
  • Progress Tracking: Track the progress of each task against the checklist.
  • Communication: Keep users informed of any delays or unexpected issues.

If you encounter problems, refer to your rollback plan. Don’t hesitate to seek help from other administrators or the MediaWiki community. The MediaWiki mailing lists and MediaWiki IRC channel are excellent resources.

Post-Shutdown Verification

After the shutdown is complete, thoroughly verify that the wiki is functioning correctly.

  • Functional Testing: Test all critical wiki features, including viewing pages, editing pages, searching, creating accounts, and using extensions.
  • Performance Testing: Monitor server resource usage to ensure performance is as expected. Use tools like WebPageTest to analyze page load times.
  • Database Integrity: Run database consistency checks to ensure the database is not corrupted.
  • User Feedback: Encourage users to report any issues they encounter.

Advanced Considerations

  • Load Balancing: If your wiki uses a load balancer, you may be able to take individual servers offline for maintenance while leaving the rest of the cluster online. This minimizes downtime but requires careful configuration and testing.
  • Database Replication: Using database replication allows you to perform maintenance on a replica database without affecting the primary database. This can significantly reduce downtime for database maintenance tasks.
  • Zero-Downtime Deployments: More complex deployment strategies, such as blue-green deployments, can achieve near-zero downtime deployments. These strategies involve maintaining two identical environments (blue and green) and switching traffic between them. This requires significant infrastructure and automation.
  • Caching: Effective caching strategies (e.g., using Varnish, Memcached, or MediaWiki’s built-in caching) can reduce the impact of downtime on users. Even during a shutdown, cached content may still be served, providing a limited level of functionality.

Resources and Further Reading

MediaWiki requires diligent maintenance, and scheduled shutdowns are an integral part of that process. By planning carefully, communicating effectively, and following best practices, you can minimize disruption and ensure the long-term health and reliability of your wiki.

Help:Contents MediaWiki configuration MediaWiki extensions MediaWiki database MediaWiki security MediaWiki performance MediaWiki administration MediaWiki upgrades MediaWiki backups Special:Statistics

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