Full Update vs. Rolling Update

Full updates and rolling updates are two common methods for system updates, particularly in service deployment and application upgrades. Here’s a comparison of their differences and characteristics:

1. Full Update

• Definition: A full update replaces all service instances or system components at once during the update process.
• Characteristics:
  • Completed Quickly: Since everything is replaced at once, the update process is typically fast.
  • Service Interruption: This often requires a short downtime, causing the service to be unavailable (unless a blue-green deployment or similar technique is used to minimize disruption).
  • Higher Risk: Replacing everything at once can make rollback difficult if issues arise.
• Suitable Scenarios: Ideal for smaller systems, updates during low-traffic periods, or applications that do not require high business continuity.

2. Rolling Update

• Definition: A rolling update gradually replaces service instances, updating the system in phases.
• Characteristics:
  • Phased Update: Only a subset of instances is updated at a time, with the remaining instances continuing to serve traffic. After one batch is updated, the next batch is updated.
  • No Service Interruption: Since some instances are always available, the service typically remains uninterrupted.
  • Lower Risk: Allows for real-time monitoring during the update. If issues occur, the update can be paused or rolled back.
• Suitable Scenarios: Suitable for systems with high availability requirements, especially in microservices architectures or containerized environments (e.g., Kubernetes), where the service must remain available during the update process.

Summary

• Full Update is simpler and faster but has downtime risks and higher rollback costs.
• Rolling Update is preferred for systems requiring high availability, allowing updates without downtime and enabling easier monitoring and rollback.