Use-cases for reactive streams using java 9 Flows in Servlets?

Question

I'm looking for use-cases for using reactive streams within a servlet container (or just a HTTP server).

The Jetty project has started being asked: "is Jetty reactive?" and we've noticed the proposal to add reactive streams to java 9.

So we've started some experiments with using the reactive streams API for async servlet IO, which are interesting enough..... but lack any focus because we lack real use-cases to focus which concerns are most important.

So does anybody have any good use-cases that they could share/explain so that we can direct our jetty experiments to meet their needs. The sort of thing I've imagined is having a RS based database publisher sending objects all the way out on a HTTP response or websocket connection using Flow.Processors for the conversions along the way.

Answer 1

A viable use case is when consuming the POSTing of multi-part form data, particularly when uploading files.

The Typesafe ConductR project (disclaimer: I'm the Tech Lead for it), receives multi-part form data when a user loads a bundle. We use akka-streams/http.

We read off the first two parts of the stream as our protocol specifies that they must declare some meta data in order for us to know which node to write the bundles to. After some validation, we then determine the node to write them to, and connect the partially consumed stream. Thus the node that receives the request to upload the bundle negotiates which node it is going to write it to, while not having to consume the entire stream (which could be 200MB) and then write it out again.

Writing out multi-part form data is also a great use-case given that you can stream the file from disk as a source and pass it on to some http endpoint i.e. the client-side of what I describe above.

The benefits with both use-cases are that you minimise the amount of memory needed to move bytes over a network, and you only perform file IO where it is necessary.