Customers use Amazon OpenSearch Service for mission-critical applications and monitoring. But what happens when OpenSearch Service itself is unavailable? If your ecommerce search is down, for example, you’re losing revenue. If you’re monitoring your application with OpenSearch Service, and it becomes unavailable, your ability to detect, diagnose, and repair issues with your application is diminished. In these cases, you may suffer lost revenue, customer dissatisfaction, reduced productivity, or even damage to your organization’s reputation.
OpenSearch Service offers an SLA of three 9s (99.9%) availability when following best practices. However, following those practices is complicated, and can require knowledge of and experience with OpenSearch’s data deployment and management, along with an understanding of how OpenSearch Service interacts with AWS Availability Zones and networking, distributed systems, OpenSearch’s self-healing capabilities, and its recovery methods. Furthermore, when an issue arises, such as a node becoming unresponsive, OpenSearch Service recovers by recreating the missing shards (data), causing a potentially large movement of data in the domain. This data movement increases resource usage on the cluster, which can impact performance. If the cluster is not sized properly, it can experience degraded availability, which defeats the purpose of provisioning the cluster across three Availability Zones.
Today, AWS is announcing the new deployment option Multi-AZ with Standby for OpenSearch Service, which helps you offload some of that heavy lifting in terms of high frequency monitoring, fast failure detection, and quick recovery from failure, and keeps your domains available and performant even in the event of an infrastructure failure. With Multi-AZ with Standby, you get 99.99% availability with consistent performance for a domain.
In this post, we discuss the benefits of this new option and how to configure your OpenSearch cluster with Multi-AZ with Standby.
The OpenSearch Service team has incorporated years of experience running tens of thousands of domains for our customers into the Multi-AZ with Standby feature. When you adopt Multi-AZ with Standby, OpenSearch Service creates a cluster across three Availability Zones, with each Availability Zone containing a complete copy of data in the cluster. OpenSearch Service then puts one Availability Zone into standby mode, routing all queries to the other two Availability Zones. When it detects a hardware-related failure, OpenSearch Service promotes nodes from the standby pool to become active in less than a minute. When you use Multi-AZ with Standby, OpenSearch Service doesn’t need to redistribute or recreate data from missing nodes. As a result, cluster performance is unaffected, removing the risk of degraded availability.
Multi-AZ with Standby requires the following prerequisites:
- The domain needs to run on OpenSearch 1.3 or above
- The domain is deployed across three Availability Zones
- The domain has three (or a multiple of three) data notes
- You must use three dedicated cluster manager (master) nodes
Refer to Sizing Amazon OpenSearch Service domains for guidance on sizing your domain and dedicated cluster manager nodes.
Configure your OpenSearch cluster using Multi-AZ with Standby
You can use Multi-AZ with Standby when you create a new domain, or you can add it to an existing domain. If you’re creating a new domain using the AWS Management Console, you can create it with Multi-AZ with Standby by either selecting the new Easy create option or the traditional Standard create option. You can update existing domains to use Multi-AZ with Standby by editing their domain configuration.
The Easy create option, as the name suggests, makes creating a domain easier by defaulting to best practice choices for most of the configuration (the majority of which can be altered later). The domain will be set up for high availability from the start and deployed as Multi-AZ with Standby.
While choosing the data nodes, you should choose three (or a multiple of three) data nodes so that they are equally distributed across each of the Availability Zones. The Data nodes table on the OpenSearch Service console provides a visual representation of the data notes, showing that one of the Availability Zones will be put on standby.
Similarly, while selecting the cluster manager (master) node, consider the number of data nodes, indexes, and shards that you plan to have before deciding the instance size.
After the domain is created, you can check its deployment type on the OpenSearch Service console under Cluster configuration, as shown in the following screenshot.
While creating an index, make sure that the number of copies (primary and replica) are multiples of three. If you don’t specify the number of replicas, the service will default to two. This is important so that there is at least one copy of the data in each Availability Zone. We recommend using an index template or similar for logs workloads.
OpenSearch Service distributes the nodes and data copies equally across the three Availability Zones. During normal operations, the standby nodes don’t receive any search requests. The two active Availability Zones respond to all the search requests. However, data is replicated to these standby nodes to ensure you have a full copy of the data in each Availability Zone at all times.
Response to infrastructure failure events
OpenSearch Service continuously monitors the domain for events like node failure, disk failure, or Availability Zone failure. In the event of an infrastructure failure like an Availability Zone failure, OpenSearch Services promotes the standby nodes to active while the impacted Availability Zone recovers. Impact (if any) is limited to the in-flight requests as traffic is weighed away from the impacted Availability Zone in less a minute.
You can check the status of the domain, data node metrics for both active and standby, and Availability Zone rotation metrics on the Cluster health tab. The following screenshots show the cluster health and metrics for data nodes such as CPU utilization, JVM memory pressure, and storage.
The following screenshot of the AZ Rotation Metrics section (you can find this under Cluster health tab) shows the read and write status of the Availability Zones. OpenSearch Service rotates the standby Availability Zone every 30 minutes to ensure the system is running and ready to respond to events. Availability Zones responding to traffic have a read value of 1, and the standby Availability Zone has a value of 0.
Several improvements and guardrails have been made for this feature that offer higher availability and maintain performance. Some static limits have been applied that are specifically related to the number of shards per node, number of shards for a domain, and the size of a shard. OpenSearch Service also enables Auto-Tune by default. Multi-AZ with Standby restricts the storage to GP3- or SSD-backed instances for the most cost-effective and performant storage options. Additionally, we’re introducing an advanced traffic shaping mechanism that will detect rogue queries, which further enhances the reliability of the domain.
We recommend evaluating your domain infrastructure needs based on your workload to achieve high availability and performance.
Multi-AZ with Standby is now available on OpenSearch Service in all AWS Regions globally where OpenSearch service is available, except US West (N. California), and AWS GovCloud (US-Gov-East, US-Gov-West). Try it out and send your feedback to AWS re:Post for Amazon OpenSearch Service or through your usual AWS support contacts.
About the authors
Prashant Agrawal is a Sr. Search Specialist Solutions Architect with Amazon OpenSearch Service. He works closely with customers to help them migrate their workloads to the cloud and helps existing customers fine-tune their clusters to achieve better performance and save on cost. Before joining AWS, he helped various customers use OpenSearch and Elasticsearch for their search and log analytics use cases. When not working, you can find him traveling and exploring new places. In short, he likes doing Eat → Travel → Repeat.
Rohin Bhargava is a Sr. Product Manager with the Amazon OpenSearch Service team. His passion at AWS is to help customers find the correct mix of AWS services to achieve success for their business goals.