Rapidly expand the reach of Spanner databases with read-only replicas and zero-downtime moves

As Google Cloud’s fully managed relational database that offers near unlimited scale, strong consistency, and availability up to 99.999%, Cloud Spanner powers applications at any scale in industries such as financial services, games, retail, and healthcare. 

When you set up a Spanner instance, you can choose from two different kinds of configurations: regional and multi-regional. Both configuration types offer high availability, near unlimited scale, and strong consistency. Regional configurations offer 99.99% availability and can survive zone outages. Multi-regional configurations offer 99.999% availability and can survive two zone outages and entire regional outages.

Today, we’re announcing a number of significant enhancements to Spanner’s regional and multi-regional capabilities: 

• Configurable read-only replicas let you add read-only replicas to any regional or multi-regional Spanner instance to deliver low latency reads to clients in any geography

• Spanner’s zero-downtime instance move service gives you the freedom to move your production Spanner instances from any configuration to another on the fly, with zero downtime, whether it’s regional, multi-regional, or a custom configuration with configurable read-only replicas 

• We’re also dropping the list prices of our nine-replica global multi-regional configurations nam-eur-asia1 and nam-eur-asia3 to make them even more affordable for global workloads

Let’s take a look at each of these enhancements in a bit more detail. 

Configurable read-only replicas

One of Spanner’s most powerful capabilities is its ability to deliver high performance across vast geographic territories. Spanner achieves this performance with read-only replicas. As its name suggests, a read-only replica contains an entire copy of the database and it can serve stale reads without requiring a round trip back to the leader region. In doing so, read-only replicas deliver low latency stale reads to nearby clients and help increase a node’s overall read scalability.

For example, a global online retailer would likely want to ensure that its customers worldwide can search and view products from its catalog efficiently. This product catalog would be ideally suited for Spanner’s nam-eur-asia1 multi-region configuration, which has read/write replicas in the United States and read-only replicas in Belgium and Taiwan. This would ensure that customers can view the product catalog with low latency around the globe.

Until today, read-only replicas were available in several multi-region configurations: nam6, nam9, nam12, nam-eur-asia1, and nam-eur-asia3. But now, with configurable read-only replicas, you can add read-only replicas to any regional or multi-regional Spanner instance so that you can deliver low-latency stale reads to clients everywhere. 

To add read-only replicas to a configuration, go to the Create Instance page in the Google Cloud console. You’ll now see a “Configure read-only replicas” section. In this section, select the region for the read-only replica, along with the number of replicas you want per node, and create the instance. It’s as simple as that! 

The following snapshot shows how to add a read-only replica in us-west2 (Los Angeles) to the nam3 multi-regional configuration.

As we roll out configurable read-only replicas, we do not yet offer read-only replicas in every configuration/region pair. If you find that your desired read-only replica region is not yet listed, simply fill out this request form.

Configurable read-only replicas are available today for $1/replica/node-hour plus storage costs. Full details on pricing are available at Cloud Spanner pricing. 

Also announcing: Spanner’s zero-downtime instance move service

Now that you can use configurable read-only replicas to create new instance configurations that are tailored to your specific needs, how can you migrate your current Spanner instances to these new configurations without any downtime? Spanner database instances are mission critical and can scale to many petabytes and millions of queries per second. So you can imagine that moving a Spanner instance from one configuration to another — say us-central1 in Iowa to nam3 with a read-only replica in us-west2 — is no small feat. Factor in Spanner’s stringent availability of up to 99.999% while serving traffic at extreme scale, and it might seem impossible to move a Spanner instance from us-central1 to nam3 with zero downtime.

However, that’s exactly what we’re announcing today! With the instance move service, now generally available, you can request a zero-downtime, live migration of your Spanner instances from any configuration to any other configuration — whether they are regional, multi-regional, or custom configurations with configurable read-only replicas. 

To request an instance move, select “contact Google” in the Edit Instance of the Google Cloud Console and fill out the instance move request form. Once you make a move request, we’ll contact you to let you know the start date of your instance configuration move, and then move your configuration with zero downtime and no code changes while preserving the SLA guarantees of your configuration. 

When moving an instance, both the source and destination instance configurations are subject to hourly compute and storage charges, as outlined in Cloud Spanner pricing. Depending on your environment, instance moves can take anywhere from a few hours to a few days to complete. Most importantly, during the instance move, your Spanner instance continues to run without any downtime, and can continue to rely on Spanner’s high availability, near unlimited scale, and strong consistency to serve your mission-critical production workloads. 

Price drops for global 9-replica Spanner multi-regional configurations

Finally, we’re also pleased to announce that we’re making it even more compelling to use Spanner’s global configurations of nam-eur-asia1 and nam-eur-asia3 by dropping the compute list price of these configurations from $9/node/hour to $7/node/hour. With write quorums in North America and read-only replicas in both Europe and Asia, these configurations are perfectly suited for global applications with strict performance requirements and 99.999% availability. And now, they’re even more cost-effective to use!

Learn more 

• If you are new to Spanner, try Spanner at no charge with a 90-day free trial instance.

• Learn more about multi-regional Spanner configurations by reading Demystifying Cloud Spanner multi-region configurations