Back-end systems such as access control systems, telemetry capturing systems, quota enforcement systems, billing systems, and so on traditionally directly integrate with services, which creates a hard coupling, and it bakes in specific semantics and usage options.
Istio Mixer provides a generic intermediation layer between app code and infrastructure back ends. Its design moves policy decisions out of the app layer and into configuration instead under operator control. Instead of having app code integrate with specific back ends, the app code instead does a fairly simple integration with Mixer, and Mixer takes responsibility for interfacing with the back-end systems.
Because individual infrastructure back ends each have different interfaces and operational models, Mixer needs custom code to deal with each, and these custom bundles of code are called adapters.
Here are some built-in adapters:
- Denier
- Prometheus
- Memquota (memory quota)
- Stackdriver
