When to choose between Open Service Mesh and Dapr?

Dapr is not positioned as a service mesh but has overlapping features, such as enabling mTLS across sidecars (Dapr or OSM sidecars). Dapr was designed from the ground up to build microservices-based architectures, as it enables service discovery, asynchronous communication, and event-driven architectures, which are mainstream in the microservices world.

Dapr is only intended to be used with HTTP and GRPC protocols. On the other hand, OSM is not restricted to these application protocols and can also help with raw TCP.

Here are some scenarios that may help you choose between them or use them together:

• You deal with microservices only and host nothing but stateless services in your clusters è use Dapr
• You have legacy apps and want to control the flows and the way they interact with each other use OSM
• You have a mix of both hosted in the same cluster use both
• You need to enable scenarios such as A/B testing, Blue/Green, etc. Use OSM or both, but OSM is required.

If you use both together, you should disable Dapr’s mTLS and rely on OSM one. At last, a significant difference between Dapr and OSM is that Dapr is used explicitly by the application container while OSM is silently (if everything goes well 😊) injecting the app.