Runbook for Zero Downtime ClickHouse Upgrades

ClickHouse Upgrade

Table of Contents

Introduction

In the world of data analytics and high-performance databases, ClickHouse stands out for its speed, efficiency, and scalability. As organizations increasingly rely on real-time data processing and analytics, the need for maintaining continuous availability of the database system becomes paramount. One of the critical challenges faced by database administrators (DBAs) is performing upgrades without causing downtime, which can disrupt services and impact business operations. This is where zero downtime upgrades come into play.

What are Zero Downtime Upgrades?

Zero downtime upgrades refer to the process of upgrading the database software or infrastructure without interrupting the availability of the service to users. This means that during the upgrade, the database continues to operate, handle queries, and provide data access as usual. Achieving zero downtime upgrades ensures seamless transitions and continuous operations, which are crucial for mission-critical applications.

Step-by-step Zero Downtime Upgrades

Step 1: Set up a standby cluster

  • Clone your existing ClickHouse cluster to create a standby cluster.
  • Set up replication between the existing and the standby clusters to ensure that the data is up-to-date.

Step 2: Upgrade ClickHouse on the standby cluster

  • Follow the standard upgrade process for ClickHouse on the standby cluster.
  • Ensure that the upgrade is successful and there are no issues.

Step 3: Test the upgraded standby cluster

  • Run tests on the upgraded standby cluster to ensure that everything is functioning correctly.
  • Monitor the standby cluster to ensure that there are no issues.

Step 4: Switch traffic to the standby cluster

  • Update the DNS records or load balancer settings to route traffic to the upgraded standby cluster.
  • Ensure that traffic is flowing to the standby cluster.

Step 5: Upgrade ClickHouse on the main cluster

  • Follow the standard upgrade process for ClickHouse on the main cluster.
  • Ensure that the upgrade is successful and there are no issues.

Step 6: Test the upgraded main cluster

  • Run tests on the upgraded main cluster to ensure that everything is functioning correctly.
  • Monitor the main cluster to ensure that there are no issues.

Step 7: Switch traffic back to the main cluster

  • Update the DNS records or load balancer settings to route traffic back to the main cluster.
  • Ensure that traffic is flowing to the main cluster.

Step 8: Monitor the system

  • Monitor the ClickHouse system to ensure that there are no issues after the upgrade process.
  • Identify and resolve any problems as soon as possible to minimize downtime.

Step 9: Rollback plan

  • Have a rollback plan in place in case any issues occur during the upgrade process.
  • Test the rollback plan to ensure that it works as expected.

Conclusion

By following the above steps, you can implement zero downtime ClickHouse upgrades. It’s essential to test and monitor the system at every step to ensure that there are no issues and to take corrective actions if any problems arise.

To read more articles on ClickHouse internals, do consider reading the below articles

About Shiv Iyer 236 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.