stream-url

Stream URLs

The package aims to unite two powerful universal concepts: streams and URLs. It is mostly driven by desire to create modular distributed applications connected by asynchronous interfaces. Consider typical microservices. Those are connected by HTTP request-response calls thus emulating a synchronous call graph in a fundamentally asynchronous environment. Stream-connected architectures can be seen as distributed go channels instead.

Streams allow to pipeline operations, provide flow control, and, most importantly, the concept of a stream is universal enough to use in very different settings.

For example, one may use loopback streams for testing, filesystem sockets to connect local processes, WebSockets to pass data over the internet and raw TCP streams for low-overhead inner network transmissions. Considering isomorphic apps, inside the browser one may use postMessage (frame to frame) or WebStorage (tab to tab) based streams.

This approach fits event sourcing architectures extremely well, as all app's events are well serializable then.

So, stream-url encapsulates details of a particular medium and allows the app to open data streams to URLs. stream-url is a syntactic sugar, in a sense, or maybe even syntactic cocaine, but it definitely helps to clear a subsystem's code out of technical details and make it easily pluggable. Just replace loopback://random_key for ws://myserver.com or tcp://10.10.10.10:1234 and the component/micro-service now works in a different setting.

API

• listen(url [,options] [,callback]) start a server (stream factory) listening at the url, using options. Invoke callback(err, server) when ready or failed. The server will emit a connection event for every new incoming connection/stream.
• connect(url [,options] [,callback]) connect to a server at (create a stream to) url. Invoke callback(err, stream) once ready to write or failed to connect. The stream will emit all the usual events: data, end, error.

This package defines just one fictive URL protocol named 0 which masquerades local invocations for a stream. The 0 protocol is mostly useful for connecting componenets locally. It is not that useful for unit testing as it skips serialization/ deserialization for the sake of efficiency. See test/ for usage examples.

All "real" protocols are defined in separate packages, as those introduce non-trivial dependencies.

• server-side WebSocket
• TCP
• HTTP
• filesystem sockets
• stdin/stdout
• client-side WebSocket
• postMessage
• WebStorage
• loopback streams