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Architecture Overview

Executor and Flow are the two fundamental concepts in Jina.

The figure below shows details on how the Flow and Executor abstractions translate into concrete entities, providing all the serving and scaling features of Jina.

It illustrates how Jina deploys and serves its Flows and Executors.

You will not need to understand every detail of this architecture in order to build your first Neural Search app using Jina. But it is useful in order to understand how Jina works, regardless of whether it runs locally, orchestrated only by the Flow, or in a cloud-native infrastructure such as Kubernetes. In fact, you can notice how some naming and concepts are inspired by the Kubernetes architecture.

The following concepts may appear in the docs, but you don’t need to master them as they are designed to be used only internally:

• Gateway: The Gateway is a service started by the Flow which is responsible for exposing the HTTP, WebSocker or gRPC endpoints to the client. Additionally, it keeps knowledge of the topology of the Flow to guarantee that the Documents are processed by the Executors in the proper order. It communicates with the Deployments via gRPC

• Deployment: Deployment is an abstraction around Executor that lets the Gateway communicate with an Executor. It encapsulates and abstracts internal replication details.

• Pod: A Pod is a simple abstraction over a runtime that runs any Jina service, be it a process, a Docker container, or a Kubernetes Pod.

• Head: The Head is a service added to a Deployment by Jina, and it ensures that load is balanced between all replicas of a given Executor. It communicates with the Executors via gRPC.