consolidating collect functions for multiple metrics

[InsOpDe]

I have the following example:

const employeeMetric = new promClient.Gauge({
			async collect(): Promise<void> {
				const employees = await that.getAllEmployees()
				this.set({}, employees.length)
			},
			help: "Employees",
			labelNames: ["service"],
			name: `employees_all`
		})
const employeeOvertimeHoursMetric = new promClient.Gauge({
			async collect(): Promise<void> {
				const employees = await that.getAllEmployees()
				const overTimeHours = employees.reduce((acc, curr) => acc + curr.overTimeHours, 0)
				this.set({}, overTimeHours)
			},
			help: "Employees overtime hours",
			labelNames: ["service"],
			name: `employees_overtime_hours`
		})

Now getAllEmployees is a very expensive query, which takes some time to retrieve. And that's rather bad if we have to call this method for each metric.

I could however add to the second collect-function the following snippet:

employeeMetric.set({}, employees.length)

and leave out the collect-function of the first metric. But now we have a running condition - which collect function is called first, and is it fast enough? should I rather add a setTimeout(Promise.resolve(),500) into the first collect-function so it doesnt resolve before the value is set in the second collect-function?

now I have more metrics I want to collect for the hypothetical employees

what is the best way to solve this?

[zbjornson]

I think we'd need to add some registry-level hook/event for this that tells you "collect is about to be called," but that has some risk too if there are concurrent collections for some reason.

Could you do something like this as a workaround?

let employees;
let nCollected = 0;

// in each metric
collect() {
  if (!employees)
    employees = await getAllEmployees();
  this.set({}, /* value */);
  nCollected++;
  if (nCollected === 2) {
    employees = null;
    nCollected = 0;
  }
}

[InsOpDe]

thats indeed a workaround - thanks.

(Id be happier if a better solution exists - maybe something where a collection can hook onto another collection)

---

however I will just cache getAllEmployees with memoize

[jseparovic]

Would be nice to be able to create multiple metrics at the same time using a common collect function.

Something like:

new Gauges(
    {
        metrics: [
            {    
                name: "mode_normal",
                help: 'Total number of hosts in Normal Mode',
            },
            {
                name: "mode_low_power",
                help: 'Total number of hosts in Low Power Mode',
            },
            {
                name: "mode_sleep",
                help: 'Total number of hosts in Sleep Mode',
            }
        ],
        async collect() {
            const modes = await getHostMode();
            this.set([
                {
                    name: 'mode_normal',
                    value: modes.Normal
                },
                {
                    name: 'mode_low_power',
                    value: modes.LowPower
                },
                {
                    name: 'mode_sleep',
                    value: modes.Sleep
                },
            ]);
        }
});

Then when collect runs, the set function could update all metrics at once.

[jseparovic]

Would be nice to be able to create multiple metrics at the same time using a common collect function.

Something like:

new Gauges(
    {
        metrics: [
            {    
                name: "mode_normal",
                help: 'Total number of hosts in Normal Mode',
            },
            {
                name: "mode_low_power",
                help: 'Total number of hosts in Low Power Mode',
            },
            {
                name: "mode_sleep",
                help: 'Total number of hosts in Sleep Mode',
            }
        ],
        async collect() {
            const modes = await getHostMode();
            this.set([
                {
                    name: 'mode_normal',
                    value: modes.Normal
                },
                {
                    name: 'mode_low_power',
                    value: modes.LowPower
                },
                {
                    name: 'mode_sleep',
                    value: modes.Sleep
                },
            ]);
        }
});

Then when collect runs, the set function could update all metrics at once.

Just realized I should be using labels for this instead, not multiple metrics.