Node Service Status

This library provides a mechanism to generate an object from a list of service status monitors and provdies the ability to either run all monitors or just one.

Requirements

A modern Node that understands classes and async/await.

Usage

npm install --save @elvenspellmaker/node-service-status

Then define a monitor, create a class extending the ServiceStatusMonitor class, making sure to override both the name() and run() methods. Note: run() may be an async method returning a Promise, however name() should NOT be.

"use strict";

const ServiceStatusMonitor = require('@elvenspellmaker/node-service-status').ServiceStatusMonitor;

class DbCanConnectMonitor extends ServiceStatusMonitor
{
	// Some constructor taking in a db

	name()
	{
		return 'db-can-connect';
	}

	async run()
	{
		return await this.db.auth();
	}
}

Monitors should return Boolean true if successful and any other value if unsuccessful. Promises will be resolved and unpacked to see if the value is Boolean true.

In order to consume service status monitors, create an instance of ServiceStatus and pass in an array of monitors.

const ServiceStatus = require('@elvenspellmaker/node-service-status').ServiceStatus;
const DbCanConnectMonitor = require('../monitor/DbCanConnectMonitor');

const ss = new ServiceStatus([
	new DbCanConnectMonitor(db),
]);

Then by calling runMonitors() or runMonitor(monitorName) you may run all monitors or a single monitor. The returned object will either be a single status object or an object containing all the statuses and the overall status. Both object types have a top-level parameter successful which gives the overall success of the monitors. For example as JSON:

{
	"successful": false,
	"monitors": [
		{
			"successful": true,
			"monitorName": "true-monitor"
		},
		{
			"successful": false,
			"monitorName": "false-monitor"
		}
	]
}

or

{
	"successful": false,
	"monitorName": "false-monitor"
}

If calling the runMonitors() method, all monitors will be run and will resolve eventually and so the method must be awaited if the value is wanted, such as to output from a route:

const ssResult = await ss.runMonitors();

If calling the runMonitor() method and the passed monitor name is not found, null will be returned which indicates that the monitor does not exist. It is suggested this would be treated as a 404 by your application.

If calling either method and the top-level successful key is false this means one or more of the monitors has failed and it is suggested this is treated as a 503 by your application as the service is broken in some way.

If calling either method and the top-level successful key is true all monitors passed and it is suggested that this would be treated as a 200 by your application.

Notes

1. Name should NOT be async, and should return a string. If the name method is is missing then a name will be generated in the form of missing-name-<<number>> where missing number is incremented for each monitor with a missing name, and this monitor will always return false to indicate failure.
2. With the default logger, when NODE_ENV environment variable is set, any Errors will be console logged and the service status will continue as gracefully as possible. In all other environments any Errors will be thrown as Errors for easier debugging.