What deployment method allows gathering performance metrics using live traffic prior to launching an application?

The deployment method that allows for the gathering of performance metrics using live traffic prior to launching an application is A/B testing with traffic mirroring. This approach involves deploying multiple versions of an application in the production environment and directing a portion of live traffic to these different versions. By mirroring traffic to the new version while still serving the majority of users from the stable version, developers can monitor how the new version performs in real-world conditions.

This method allows for a comprehensive evaluation of performance metrics, user behavior, and other critical factors without fully committing to the new version. It also helps identify potential issues in a controlled scenario, as developers can analyze how the new version behaves under load with actual users before a complete rollout.

In contrast, while canary deployment focuses on gradually rolling out a new version to a small subset of users, blue/green deployment involves switching between two distinct environments and does not typically gather metrics in the same live traffic manner before a full launch. Rolling updates allow for gradual updates, but again, they do not fundamentally include the mirroring aspect that A/B testing involves, which is crucial for real-time performance analysis.