Flow is a Clojure library that provides Clojure protocols which closely match
with the Java interfaces defined by Reactive
Streams and standardised as java.util.concurrent.Flow in JDK 9 and above.
This interface provides a common standard allowing JUXT libraries to integrate data streams with back-pressure, and interoperate with other libraries that support the Reactive Streams standard, such as RxJava.
The JVM interfaces created by Reactive Streams (Processor, Publisher,
Subscriber, Subscription) are published in the org.reactivestreams
package
and in the Java 9 JDK itself, wrapped in the java.util.concurrent.Flow class.
Eventually, all compatible JVM libraries are expected to upgrade to the JDK 9 interfaces. However, while Java 8 is still in use, Clojure protocols can be used to adapt between these Java interfaces and the various library classes that implement them, allowing a mix of 'old' and 'new' implementations.
Flow plays a similar role to Manifold. Both are written to simplify programming with asynchronous IO with back-pressure.
(T)he plan is to have NIO protocols that the request body and response body can optionally satisfy.
ring-clojure/ring#393 (comment)
Flow is proposed for consideration as a candidate for these NIO protocols, which
if accepted, would mean the juxt.flow namespace prefix could be replaced with
one in the ring namespace hierarchy.
The aim is to provide working code examples to demonstrate the sufficiency of Flow’s protocols in implementing various use-cases of async non-blocking IO with back-pressure using Ring, including streaming request and response bodies, websockets and server-sent events.
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