Design considerations for hybrid applications - Resiliency
This article was authored by AzureCAT Marc van Eijk. It was edited by Bruce Hamilton and reviewed by Damir Bersinic, Gavin Kemp, Daniel Neumann, and Emmanuel Sache.
Table of Contents:
- Overview
- Placement
- Scalability
- Availability
- Resiliency- This article
- Manageability
- Security
- Summary & Learn more
Resiliency
Resiliency is the ability for a hybrid application and system to recover from failures and continue to function. The goal of resiliency is to return the application to a fully functioning state after a failure occurs. Resiliency strategies include solutions like backup, replication, and disaster recovery.
For the core discussion of this pillar, see Resiliency in Pillars of software quality.
Resiliency checklist
Uncover disaster-recovery dependencies. Disaster recovery in one cloud might require changes to application components in another cloud. If one or multiple components from one cloud are failed over to another location, either within the same cloud or to another cloud, the dependent components need to be made aware of these changes. This also includes the connectivity dependencies. Resiliency requires a fully-tested application recovery plan for each cloud.
Establish recovery flow. An effective recovery flow design has evaluated application components for their ability to accommodate buffers, retries, retrying failed data transfer, and, if necessary, fall back to a different service or workflow. You must determine what backup mechanism to use, what its restore procedure involves, and how often it’s tested. You should also determine the frequency for both incremental and full backups.
Test partial recoveries. A partial recovery for part of the application can provide reassurance to users that all is not unavailable. This part of the plan should ensure that a partial restore doesn’t have any side effects, such as a backup and restore service that interacts with the application to gracefully shut it down before the backup is made.
Determine disaster-recovery instigators and assign responsibility. A recovery plan should describe who, and what roles, can initiate backup and recovery actions in addition to what can be backed up and restored.
Compare self-healing thresholds with disaster recovery. Determine an application’s self-healing capabilities for automatic recovery initiation and the time required for an application’s self-healing to be considered a failure or success. Determine the thresholds for each cloud.
Verify availability of resiliency features. Determine the availability of resiliency features and capabilities for each location. If a location does not provide the required capabilities, consider integrating that location into a centralized service that provides the resiliency features.
Determine downtimes. Determine the expected downtime due to maintenance for the application as a whole and as application components.
Document troubleshooting procedures. Define troubleshooting procedures for redeploying resources and application components.
Next Article: Manageability