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