4. Server API

Apart from the HTTP Client Akka HTTP also provides an embedded, Reactive-Streams-based, fully asynchronous HTTP/1.1 server implemented on top of StreamsStreams.

It supports the following features:

Full support for HTTP persistent connections
Full support for HTTP pipelining
Full support for asynchronous HTTP streaming including “chunked” transfer encoding accessible through an idiomatic API
Optional SSL/TLS encryption
WebSocket support

The server-side components of Akka HTTP are split into two layers:

Core Server API: The basic low-level server implementation in the akka-http-core module.
High-level Server-Side API: Higher-level functionality in the akka-http module which offers a very flexible “Routing DSL” for elegantly defining RESTful web services as well as functionality of typical web servers or frameworks, like deconstruction of URIs, content negotiation or static content serving.

Depending on your needs you can either use the low-level API directly or rely on the high-level Routing DSL which can make the definition of more complex service logic much easier. You can also interact with different API levels at the same time and, independently of which API level you choose Akka HTTP will happily serve many thousand concurrent connections to a single or many different clients.

Note

It is recommended to read the Implications of the streaming nature of Request/Response Entities section, as it explains the underlying full-stack streaming concepts, which may be unexpected when coming from a background with non-“streaming first” HTTP Servers.