strong-db-watcher
Event broadcast/watch mechanism triggered by internal database events such as Create, Update or Delete.
DbWatcher: Class, inherits EventEmitter
-
dbClient
a postgres handle already connected to the DB -
changeListener
{Function} called at every watched event with (result) where,- result: {Object}
table
{String} table nameop
{String}INSERT
,UPDATE
,INSERTorUPDATE
, orDELETE
when
{String}BEFORE
,AFTER
, orUNSPECIFIED
payload
{Object} database recordreceivedAt
{Integer} timestamp in msec since the epoch when the broadcast msg is received by the watcher, not when the broadcast event is generated by the broadcaster.
Event is emitted per each table with result {Object}. In case changeListener is set, it's called for every event in addition to event. Usage below shows how to watch events.
- result: {Object}
watchTable
name
{String} table namecallback
{Function} called with err
isWatching
returns {Boolean}
name
{String} table namefn
{Function} listener function
unwatchTable
unwatch one table
name
{String} table name,callback
{Function} called with err
close
unwatch all the watching tables
callback
{Function} called with err
Usage: notified by changeListener
var pg = require('pg');
var DbWatcher = require('strong-db-watcher');
var tableName = 'serviceinstance';
var client = new pg.Client(<connection string>);
client.connect(function(err) {
var sdw = new DbWatcher(client,
function(result) {
... all events are watched ...
... switch (result.table) case to ...
... process all events here or emit your own event ...
});
sdw.watchTable(name, function(err) {
console.log('watchTable error');
});
Usage: notified by Events
var pg = require('pg');
var DbWatcher = require('strong-db-watcher');
var tableName = 'serviceinstance';
var client = new pg.Client(<connection string>);
client.connect(function(err) {
var sdw = new DbWatcher(client);
sdw.on(name,
function(result) {
... process the result here ...
... events for the table only ...
});
sdw.watchTable(name, function(err) {
console.log('watchTable error');
});
Result:
{
table: 'serviceinstance',
op: 'UPDATE',
when: 'BEFORE',
payload:
{
executorid: 155,
serverserviceid: 1,
groupid: 1,
currentdeploymentid: 'some commit',
containerversioninfo: {},
token: 'bc1357e132318ade13dd008a882d2d0fe5fb1980e7d98c0a',
started: false,
setsize: 0,
cpus: 'CPU',
tracingenabled: false,
id: 153
},
receivedAt: 1440828036502
}