OmgImAlexis / consul-health-reporter-node

Consul health reporter for Node.js

Regularly reports health state of a Node.js app to Consul. Useful for TTL kind of checks.

Does not perform registration of a service, at least for now. If you're using Docker, check this excellent automatical service registrator.

Installation

$ npm install consul-health-reporter

The source is written in ES6, but ES5 version is provided too (generated using 6to5):

// ES6
import Reporter from 'consul-health-reporter'

// ES5
var Reporter = require('consul-health-reporter/es5')

API

Constructor

new Reporter(serviceId, opts)

Returns a new instance of reporter.

• serviceId ID of the service, which must be already registered in Consul; required.
• opts.consulAgentUrl URL of local Consul agent's HTTP interface, defaults to 'http://127.0.0.1:8500'.
• opts.intervalSec Interval between successive reports, defaults to 5 seconds. Should be smaller than TTL specified for the Consul check, to reduce the possibility of Consul assuming that the service is dead when a report was delayed due to ephemeral conditions, e.g. high CPU load.
• opts.check A function to determine current health state of the app; defaults to always reporting passing state. It is called each time health is about to be reported, and provided with three arguments: pass, warn and fail, which are functions that accept a single optional parameter, note. The check function should return the result of calling one of these functions, e.g. return pass('ok').

The reporter will not report anything until reporter.resume() is called.

resume

reporter.resume()

Starts reporting health to Consul, or resumes normal operation after calling makeWarn() or makeFail(). Sends the first report immediately.

Returns the same reporter instance.

makeWarn and makeFail

reporter.makeWarn(note)

reporter.makeFail(note)

Immediately reports warning/failure health state to Consul. Stops consulting opts.check function, assuming that health state will not change until reporter.resume() is called.

The note parameter is optional. Returns the same reporter instance.

Example

var Reporter = require('consul-health-reporter/es5');

var health = new Reporter('my-app', {
  intervalSec: 7,
  check: myAppCheck
});

function myAppCheck(pass, warn, fail) {
  if (isEverythingOk()) {
    return pass();
  }
  return fail('oh no!');
}

process.on('uncaughtException', reportAndExit);

function reportAndExit(err) {
  console.log('Error (will exit): ' + (err && err.stack || err));
  // report immediately, don't wait till the next scheduled time
  health.makeFail(err);
  // stop normal operation
  stopAcceptingRequests();
  // allow the report to reach Consul
  setTimeout(process.exit.bind(process, 1), 1000);
}

http.createServer(app.callback())

.on('error', function(err) {
  reportAndExit('cannot start server: ' + err);
})

.listen(3000, function() {
  console.log('listening on port 3000');
  // start reporting health
  health.resume();
});