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pg-ipc

IPC over PostgreSQL LISTEN/NOTIFY/UNLISTEN exposed as an EventEmitter

Usage

var pgIPC = require('pg-ipc')
var client = new require('pg').Client({ ... })

var ipc = pgIPC(client)

ipc.on('error', console.error)

ipc.on('end', function () {
  client.end()
})

ipc.on('someChannel', function (msg) {
  // Ignore messages from this process
  if (msg.processId === client.processID) return
  console.log(msg.payload.currentTime)
})

ipc.notify('someChannel', {currentTime: Date.now()})

// some time later ...

ipc.end()

API

pgIPC(client)

Instantiates a new EventEmitter with the appropriate hooks to automatically LISTEN/NOTIFY/UNLISTEN. Note that client must be a pg.Client instance and not a pg.Pool, as a single connection is required.

ipc.on(channel, listener)

All the standard EventEmitter methods are exposed. When a listener is added to channel, a LISTEN command is automatically issued, and UNLISTEN when the number of listeners reach zero. The listener will receive the message as its first argument. Notable properties being channel, payload, processId. Each postgres connection is assigned a unique processId, which can be used to ignore messages from the same process. See EventEmitter for more details. Reserved channels are: ['newListener', 'removeListener', 'notify', 'unlisten', 'listen', 'error', 'end']

ipc.notify(channel[, payload])

Alias: ipc.send(channel[, payload]). Send a message to channel with optional payload. payload is transparently converted to JSON where appropriate.

ipc.end()

Issue UNLISTEN * if connected, emit end and detach all event listeners. Does not call client.end() so you can continue using the client. However, any listeners you've issued outside outside of this module will also be detached

Event: listen

Emitted when a LISTEN has been successfully issued. Passed channel

Event: notify

Emitted after a notification has been successfully sent. Passed channel and payload

Event: unlisten

Emitted when a UNLISTEN has been successfully issued. Passed channel

Event: end

Emitted when all LISTENs have been removed, but before all event listeners are removed.

Event: error

Propagates any errors caused by queries on Client. Passed the err argument from the query callback.

Install

npm install pg-ipc

License

ISC