NREPL Middleware

• This project is used in Notebook and Goldly.
• nrepl websocket relay (browsers can not connect to normal tcp ports)
• middleware that renders evalued results
• nrepl client

Middleware cli demo

To test picasso and sniffer middleware run 3 different terminal windows and execute this 3 commands in this order

lein relay-jetty  ; this runs jetty http server with websocket relay (port 9000)
lein client sink   ; will listenn to sniffed evals
lein client ide   ; will do a few evals that wil show up on listen

WebRelay websocket demo

To see a simple websocket frontend, run in 2 terminal windows:

lein relay-jetty  ; this runs jetty http server with websocket relay (port 9000)

npm install
lein demo         ; browser app served with shadow-cljs dev server port 8000

Design of websocket relay

Server

• Browser can only do websocket and not normal sockets.
• Server Relay runs as ring request-handler, and returns new websocket handler
• the websocket handler creates a new nrel client connection, and then forwards requests in both ways.
• currently we create nrepl server to connect to.

Browser:

• The code is spit into several stateful components.
• layer1 is websocket connection. Provides two core async channels. Manages connection / reconnection.
• layer2: request router. Manages pending requests, returns for each nrepl-op a dedicated return channel, which is sent fragment by fragment. The request channel will be closed after the last fragment is received.
• layer3:

Logging:

• Lots of logging with timbre at DEBUG level
• If you dot want lots of output, set loglevel to INFO

Notes new release / notebook integration:

• make api similar to existing apis (nrepl / cojupyter / xxx)
• connect to remote nrepl without client middleware setup?

nrepl ws relay:

• relay nrepl client is stored in session, but we dont have session middleware on that route. I think it is recreating the connections for each request. ls-sessions gives me 20 sessions! for 1 browser.
• how are nrepl relay connections disgarded?
• no conflict with existing notebook implementations?

-clojail: refactor or out.