Asynchronous job scheduling in nodejs using a loop
I have JSON tasks grouped into an interval (see unit
), they must be repeated with an interval every
unit
.
items=[
{
"unit" : "minute",
"detail" :
[
{"every" : 3, task : "task1"}
{"every" : 4, task : "task2"}...
]
},
{
"unit" : "day",
"detail" :
[
{"every" : 3, task : "task3"}
{"every" : 4, task : "task4"}...
]
},..
]
I used node-cron via the following async function to schedule them at every interval every
unit
, for example: task1 should happen every 3 minutes.
I tried this code:
var CronJob = require('cron').CronJob;
function cronify(callback)
{
for (var i in items)
{
for (var j in items[i].detail) {
callback(items[i].unit,items[i].detail[j]);
}
}
}
cronify(function (duration, detail) {
var when = '* * * * * *';
switch(duration)
{
case 'minute' :
when = '* */'+detail.every+' * * * *';
break;
case 'hour' :
when = '* * */'+detail.every+' * * *';
break;
case 'day' :
when = '* * * * */'+detail.every+' * *';
break;
}
var job = new CronJob(when, function () {
//Do the task for task
}, null, true, "GMT");
}
});
But the problem is that each task is executed every second regardless of the duration specified by unit
and every
.
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Yes, if you put an asterisk (*) for a second, then the task will run every second of odd minutes in the case of * * / 2 * * * *. To run the task once per minute, you can put 0 in seconds than 0 * / 2 * * * *. Sample code:
items = [{
"unit": "minute",
"detail": [{
"every": 3,
"task": "task1"
}, {
"every": 4,
"task": "task2"
}]
}, {
"unit": "day",
"detail": [{
"every": 3,
task: "task3"
}, {
"every": 4,
task: "task4"
}]
}];
var CronJob = require('cron').CronJob;
function cronify(callback) {
for (var i in items) {
for (var j in items[i].detail) {
callback(items[i].unit, items[i].detail[j]);
}
}
}
cronify(function(duration, detail) {
var when = '* * * * * *';
switch (duration) {
case 'minute':
when = '0 */' + detail.every + ' * * * *';
break;
case 'hour':
when = '0 0 */' + detail.every + ' * * *';
break;
case 'day':
when = '0 0 0 0 */' + detail.every + ' *';
break;
}
var job = new CronJob(when, function (when) {
console.log(when);
}, null, true, "GMT");
});
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