How does Envoy achieve traffic splitting?

Envoy achieves traffic splitting primarily through weight-based routing rules, which allow for a flexible distribution of incoming traffic between different service instances based on predefined weights. This means that you can specify how much traffic should be directed to each service instance, enabling techniques such as canary deployments or blue-green deployments, where a small percentage of traffic is sent to a new version of a service while the majority continues to receive traffic from the stable version.

By assigning different weights to different versions of a service, Envoy can effectively control and gradually shift traffic as needed. This method is particularly useful for testing new features with users before fully deploying updates or alternate implementations, allowing teams to monitor performance and gather feedback without risking the entire application’s stability.

The other options may suggest alternative concepts, but they do not encapsulate the direct mechanism of traffic splitting as effectively as weight-based routing does. For instance, limiting total traffic to a fixed amount doesn't address the proportional assignment of traffic to different targets, while cloning service instances isn't a method used for splitting traffic. Even distribution across services does not provide the granularity and control that weight-based routing offers. Thus, weight-based routing rules are the fundamental mechanism supporting effective traffic splitting in Envoy.