Instructions for a Zero Downtime Migration to OpenSearch

We understand the importance of seamless transitions when migrating to OpenSearch. Zero downtime migrations are essential to ensure uninterrupted service for your users and maintain business continuity. 

In this instruction guide, we’ll walk you through the steps to achieve a zero downtime migration to OpenSearch.

Why Zero Downtime Migration to OpenSearch Matters

A zero downtime migration to OpenSearch ensures that your services remain available to users throughout the migration process. This is especially crucial for businesses that operate 24/7.

Additionally, maintaining data consistency and integrity during migration is paramount. Any data loss or corruption can lead to long-term problems and data recovery headaches.

In the following seven steps we will outline how to prepare, carry out, and maintain a migration to OpenSearch without incurring downtime.

Step 1: Prepare Your Source Environment

Before starting the migration, you will prepare your source environment. This preparation will include running a backup, possibly upgrading your current database, documenting your configuration, and an optional data cleanup. 

Backup Data: Create backups of your data to ensure you have a failsafe in case something goes wrong during migration. Read about our 4 Approaches to Data Backup for background on this topic.

Upgrade Your Current Database: Ensure your source cluster is running a compatible version with OpenSearch. You may need to perform upgrades to ensure compatibility.  

If you’re migrating from Elasticsearch, then as of December 2023, you will need to be running Elasticsearch version 6.x or 7.x to migrate to Opensearch, source.

Document Your Configuration: Document your existing cluster’s configuration, settings, and mappings. This documentation will be valuable during the migration process.

Data Cleanup: One last preparation step to consider is removing any unnecessary or outdated data from your current cluster to reduce the data volume you need to migrate. This step isn’t necessary, but it can make the migration run faster.

Step 2: Create & Configure Your Target OpenSearch Cluster

Firstly, set up a new OpenSearch cluster or ensure your existing one is ready to receive the data.

Then, carefully replicate the configurations and mappings from your source cluster to your OpenSearch cluster. This is sometimes referred to as configuration mapping, and it ensures that the data structure remains consistent.

Remember to allocate the necessary resources to your OpenSearch cluster. This will ensure it can handle the incoming data and traffic during migration.  

Step 3: Choose a Migration Approach

Three approaches to migration are a rolling upgrade, snapshot, and node replacement.

Rolling Upgrade.  A rolling upgrade will upgrade and restart the nodes in your cluster one at a time.  For comparison, a restart upgrade will upgrade the whole cluster and restart it all together.

Snapshot. This method involves taking snapshots of your source cluster and restoring them in your OpenSearch cluster. It’s a straightforward approach but may not be suitable for very large datasets. Taking a snapshot is recommended before the upgrade starts to prevent data loss (see above about backing up). Be aware that this approach of snapshot migration can incur downtime, source.

Node Replacement. A third approach is to replace existing nodes with new OpenSearch nodes. This node replacement approach is popular when upgrading Docker clusters.

Step 4: Test Your Migration Strategy

Before executing the actual migration, it’s crucial to conduct thorough testing in a controlled environment. Create a test environment that mirrors your production setup. Perform the migration there first. Learn about building and running an OpenSearch testing environment.

A proper testing environment will allow you to:

• Validate your migration strategy and identify potential issues
• Fine-tune your migration scripts and configurations
• Ensure data consistency between your source and target clusters

Step 5: Implement Data Synchronization for a Zero Downtime Migration

To achieve a zero downtime migration to OpenSearch, you’ll need to set up data synchronization between your source cluster and your OpenSearch cluster. This step ensures that any changes made during the migration process are reflected in both clusters until the migration is fully complete.

To achieve zero downtime run a real-time data sync and/or run incremental updates. 

Real-time Data Sync: Implement real-time data synchronization using tools like Elasticsearch’s Change Data Capture (CDC) or third-party solutions like Kafka.

Incremental Updates: Ensure that any new data generated in the source cluster is replicated to the OpenSearch cluster in near real-time.

Step 6: Execute the Migration

With your migration strategy thoroughly tested and refined, it’s time to execute the migration in your production environment. 

Be sure to schedule a maintenance window and notify stakeholders. Choose a time when your system experiences the least traffic.

Next, you will want to monitor the migration. Keep a close eye on the migration process using monitoring tools and logs. This allows you to detect and address any issues promptly.

And finally, run data verification after the migration is complete. You will want to check that the data in your OpenSearch cluster matches your source cluster.

Step 7: Monitor and Optimize

Post-migration, continuous monitoring and optimization are crucial for long-term success. You or your managed OpenSearch provider (such as Dattell’s Managed OpenSearch) should monitor the performance of your cluster. Make any necessary adjustments to resource allocation, shard allocation, and indexing strategies.

Additionally, continue to run preventative maintenance on your implementation. This includes running regular backups, reviewing your security configurations, and keeping current with cluster optimizations.

Conclusion

Achieving a zero downtime migration to OpenSearch is a complex but essential process. By following the steps outlined in this guide, you can minimize disruptions to your services, maintain data integrity, and ensure a seamless transition to OpenSearch. 

Remember that experience and expertise in managing OpenSearch can make a significant difference in the success of your migration. Consider partnering with a managed OpenSearch company, such as Dattell, for a smoother journey. With careful planning and execution, you can reap the benefits of OpenSearch while keeping your business operations uninterrupted.