High Availability for Appian Cloud

This configuration is available for production instances provided to Appian Cloud customers that have purchased Premier Support (including High Availability). This configuration can also be added to additional non-production instances for an additional fee.

Overview

Appian Cloud offers the ability to run in a High Availability (HA) configuration with guaranteed Recovery Point Objective (RPO) and Recovery Time Objective (RTO). The Appian Cloud HA configuration reduces the risk that your Appian instance will have from unplanned downtime caused by a number of events such as a service failure (a software component of Appian fails), a hardware failure (the underlying infrastructure hosting Appian fails) or an availability zone failure (the data center hosting the Appian Cloud instance fails).

Architecture

The Appian Cloud HA configuration is designed for resiliency and incorporates fault-tolerance in every layer of the architecture. An Appian Cloud HA instance is composed of three active nodes running in different availability zones within the same region. Data and transactions are continuously replicated across the active nodes to achieve redundancy and avoid single points of failure. The Appian Cloud Web Tier is a stateless, fault-tolerant, elastic layer that serves static content and forwards user requests to the healthy active nodes of the Appian Cloud instance.

images:cloud_ha_architecture.png

In the event of a failure affecting one of the nodes, the Appian Cloud Web Tier will automatically stop forwarding user requests to the unhealthy node. Failover occurs automatically and requests are processed by the remaining healthy nodes.

Service Level Agreements

An Appian Cloud HA instance offers an RPO of 1 minute and an RTO of 15 minutes. This means that in the event of a system failure, your Appian instance will be restored and available to your users in less than 15 minutes, having lost no more than the last 1 minute worth of data.

Appian Cloud HA is available across the globe. To see the specific regions the configuration is supported, please view the Appian Cloud Availability Table.

Prerequisites checklist

Prerequisite Description Organizational Role
Premier Support (including High Availability) Order Form This offering is available via Premier Support (including High Availability). Business relationship owner
Confirm VPN tunnel(s) connectivity details (Optional) If your Appian Cloud instance requires VPN integration, fill out the Appian Cloud VPN worksheet for the additional nodes that will be created. See Cloud VPN Integration for details. Network administrator

Steps

Once the prerequisite has been completed, follow these steps to convert your Appian Cloud instance to HA configuration:

  1. Open a Support case with the request to enable this configuration in your Appian Cloud instance(s).
    • If the site requires VPN integration, please attach the VPN worksheet completed in the prerequisite steps to the support case
  2. Appian Premier Support will schedule a maintenance window.
    • If VPN integrations are required, it is recommended that HA conversion occurs over two maintenance windows. The first window will be used to create additional nodes with VPN configuration files. This allows Appian Premier Support and the customer’s networking team to set up and confirm VPN connectivity in the additional nodes without downtime of the overall instance. The second window will be used to fully enable those additional nodes so they may begin processing requests.
  3. After the maintenance window(s), your Appian Cloud instances will be configured in HA.
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