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background

currently there is no way to connect with nsq via the browser. this is because you cannot connect to nsqd since browsers can't use http directly - you have to use websockets for bidirectional communication.

this library provides a server using nodejs that will pass messages on to nsq which are being sent to it via websocket calls.

so here is how you might use this:

  • launch nsdq
  • launch nsq-ws-bridge-nodejs
  • use nsq-ws-client-js in your browser

websocket client

i'm going to implement a client called nsq-ws-client-js which will connect to the bridge server and behave as a normal nsq client.

it is possible, though, to connect to the server using any language or system as long as it uses websockets as a transport and follows the same protocol.

protocol

websocket doesn't behave the same way as nsq, so we have to define a standard way of interpreting websocket messages as nsq ones.

test

i have a test that does all of this at once:

  • 'launches' a front-end (reads an html file into jsdom)
  • starts nsqlookupd and nsqd
  • launches an nsq client (watches for file changes)

just run node test.js and it should all work.

this is what the output looks like currently:

% node test.js
[test.js] starting server
[test.js] reading scrap/ws-client.html
[test.js] loading into jsdom
[browser] nsq.connect
[browser] nsq.connect
[test.js] spawning nsqlookupd
[test.js] spawning nsqd
[test.js] waiting one second
[ws-server-lib] ws.send sent from server (on first connection)
[browser] ws.send first connect message
[browser] reader (fs) msg: sent from server (on first connection)
[ws-server-lib] on message (type object)
[ws-server-lib]  - trying to parse object ( {"type":"handshake","topic":"fs","channel":"browser_channel"} )
[ws-server-lib]  - trying to handle object
[ws-server-lib]  - received handshake for topic fs and channel browser_channel
[ws-server-lib]  - creating nsq reader on 127.0.0.1:4161
[ws-server-lib] on message (type object)
[ws-server-lib]  - trying to parse object ( first connect message )
[ws-server-lib]  - could not parse object
[ws-server-lib] ws.send sent from server (on first connection)
[browser] ws.send first connect message
[browser] reader (reader) msg: sent from server (on first connection)
[ws-server-lib] on message (type object)
[ws-server-lib]  - trying to parse object ( {"type":"handshake","topic":"browser_topic","channel":"browser_channel"} )
[ws-server-lib]  - trying to handle object
[ws-server-lib]  - received handshake for topic browser_topic and channel browser_channel
[ws-server-lib]  - creating nsq reader on 127.0.0.1:4161
[ws-server-lib] on message (type object)
[ws-server-lib]  - trying to parse object ( first connect message )
[ws-server-lib]  - could not parse object
[test.js] starting chokidar dir watch
[chokidar-server] starting chokidar watch
[chokidar-server] writer ready
[chokidar-server] add test.js
[ws-server-lib] [nsq reader]: Received message [%s] on topic [%s]: %s 1089ad5e6423f000 fs event on test.js
[browser] reader (fs) msg: event on test.js
[browser] reader (reader) msg: event on test.js

each line is reported from a different part:

  • [test.js] is anything happening from the test.js file
  • [ws-server-lib] is from the web socket / nsq bridge server
  • [browser] is anything coming from the front-end
  • [chokidar-server'] comes from the file watching client

huh?

looking at the logs is confusing.

so the whole point of this library is to allow the browser to act as an nsq client. that's it. it can both produce messages and receive them (called Reader and Writer in the parlance ... i'm still getting use to the nsq landscape) and then any other part of the pipeline can receive them or produce messages that come through to the browser.

so, to re-iterate:

  • nsq itself has to be started (normally nsqlookupd and nsqd)
  • now any normal nsq reader/writer can communicate with it. here this is just chokidar-server which uses the nsqjs library (a standard library) to send messages onto the fs channel for any file changes (to test.js)

ok. that's just setting up nsq normally. but now in order to have the browser be an nsq client (i think i might be making up this nomenclature) we need two things:

  • the bridge needs to be started (right now called ws-server)
  • the browser needs special javascript to talk to this client (not yet a separate library ...)