hafas-client-rpc

Make JSON-RPC calls to hafas-client via

• WebSockets – Supports reconnecting and load-balancing via websocket-pool.
• stdin/stdout
• UNIX domain sockets
• NATS Streaming

Installation

npm install hafas-client-rpc

Usage

Note: This version of hafas-client-rpc only works with specific versions of hafas-client. Check peerDependencies in package.json for details.

hafas-client-rpc has multiple transports. Each of them has a client part (which sends commands to make HAFAS calls) and a server (which executes the HAFAS calls).

via WebSockets transport

With this transport, the server part is an actual WebSockets server, and the client connects to it.

// server.js
import http from 'http'
import {createClient as createHafas} from 'hafas-client'
import {profile as vbbProfile} from 'hafas-client/p/vbb/index.js'
import exposeHafasClient from 'hafas-client-rpc/ws/server'

const httpServer = http.createServer()
httpServer.listen(3000)

const hafas = createHafas(vbbProfile, 'my-awesome-program')
const server = exposeHafasClient(httpServer, hafas)

// client.js
import createRoundRobin from '@derhuerst/round-robin-scheduler'
import createClient from 'hafas-client-rpc/ws/client.js'

const pool = createClient(createRoundRobin, [
	'ws://server-address:3000'
	// pass more addresses here if you want
], (_, hafas) => {
	hafas.departures('900000009102')
	.then(console.log)
	.catch(console.error)
})
pool.on('error', console.error)

Or using the websocat command-line WebSocket client:

echo 'departures 900000009102' | websocat --jsonrpc 'ws://server-address:3000'

via stdin/stdout transport

With this transport, the client spawns the server as a sub-process and sends commands via stdio.

// server.js
import {createClient as createHafas} from 'hafas-client'
import {profile as vbbProfile} from 'hafas-client/p/vbb/index.js'
import exposeViaStdio from 'hafas-client-rpc/stdio/server.js'

const hafas = createHafas(vbbProfile, 'my-awesome-program')

exposeViaStdio(hafas, (err) => {
	console.log('hafas-client-rpc server ready')
})

Creating a client in Node.js doesn't make sense, because you could just use hafas-client directly. You would usually write the client in another language. For demonstration purposes, a Node client:

// client.js
import createClient from 'hafas-client-rpc/stdio/client.js'

createClient('path/to/stdio/server.js', (_, hafas) => {
	hafas.departures('900000009102')
	.then(console.log)
	.catch(console.error)
})

with other languages

Spawn the stdio RPC server as a sub process of your script:

node $(node -p 'require.resolve("hafas-client-rpc/stdio/simple-server.js")')

Send JSON-RPC 2.0 calls via stdin:

{"jsonrpc":"2.0","id":"1","method":"departures","params":["900000009102"]}

On success, you will receive the result via stdout:

{"jsonrpc":"2.0","id":"1","result":[{"tripId":"1|32623|3|86|8122018", …}]}

If an error occurs, you will receive it via stderr:

{"jsonrpc":"2.0","id":"1","error":{"message":"station ID must be a valid IBNR.","code":0,"data":{}}}

via UNIX domain sockets

With this transport, both client & server connect to a local TCP socket /tmp/hafas-client-rpc-{version}.

// server.js
import {createClient as createHafas} from 'hafas-client'
import {profile as vbbProfile} from 'hafas-client/p/vbb/index.js'
import exposeViaSocket from 'hafas-client-rpc/socket/server.js'

const hafas = createHafas(vbbProfile, 'my-awesome-program')

exposeViaSocket(hafas)

// client.js
import createClient from 'hafas-client-rpc/socket/client.js'

createClient((_, hafas) => {
	hafas.departures('900000009102')
	.then(console.log)
	.catch(console.error)
})

via NATS Streaming transport

This transport relies on NATS streaming channels. This allows you to have a pool of servers where an individual server can go offline at any time, as the channel will persist all RPC requests until they're taken care of. The transport uses two durable channels (one for RPC requests, the other for responses).

// server.js
import {createClient as createHafas} from 'hafas-client'
import {profile as vbbProfile} from 'hafas-client/p/vbb/index.js'
import exposeViaNatsStreaming from 'hafas-client-rpc/nats-streaming/server.js'

const hafas = createHafas(vbbProfile, 'hafas-client-rpc WebSockets example')
exposeViaNatsStreaming(hafas, (err) => {
	if (err) console.error(err)
})

// client.js
import createClient from 'hafas-client-rpc/nats-streaming/client.js'

const pool = createClient((_, hafas) => {
	hafas.departures('900000009102')
	.then(console.log)
	.catch(console.error)
})

Caveats

• hafas-client exposes the used profile as hafasClient.profile. Because these profiles consist of JavaScript functions, which can't be serialized properly, the hafas-client-rpc facade does not expose .profile.

Related

• hafas-client – JavaScript client for HAFAS public transport APIs.

Contributing

If you have a question or have difficulties using hafas-client-rpc, please double-check your code and setup first. If you think you have found a bug or want to propose a feature, refer to the issues page.