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piloted

piloted

Service discovery in node using ContainerPilot

Npm Version Node Version Build Status

Usage Example

const Piloted = require('piloted');
const Wreck = require('wreck');
 
const service = Piloted.service('customers');
Wreck.get(`http://${service.address}:${service.port}/?q=steven`, (err, res, payload) => {
  // handle error or process the payload of customer data
});

In the containerpilot.json5 file make sure to have a job to send SIGHUP to the node process when a watched service changes. For example, if you care about changes to influxdb services, the job would look like the following:

{
  name: 'onchange-influxdb',
  exec: 'pkill -SIGHUP node',
  when: {
    source: 'watch.influxdb',
    each: 'changed'
  }
}

A cache is maintained by piloted and will be refreshed anytime ContainerPilot sends a SIGHUP to the process. This will occur when there is a service change to a backend that your service depends on.

API

config(config [, callback])

Pass the containerpilot.json5 file as a parsed object. The properties that are used by piloted are consul and watches. These are used to connect to the consul server and will maintain a cache of the backends that your service watches. By default config is executed with the CONTAINERPILOT environment file, which points to either a JSON or JSON5 formatted file. Therefore, if this environment variable is set then you don't need to worry about executing config yourself.

  • config - configuration object with consul and watches properties. consul can be omitted and the values will be pulled from the environment variables:
    • CONSUL_HOST
    • CONSUL_PORT
  • callback - function to be executed after the initial cache of service data has been loaded. The function signature is (err)

If a callback is omitted, a Promise will be returned.

service(name)

Returns an object ({ address, port }) for the named service. If multiple instances of a service exist then the first one that hasn't been executed or the oldest instance to be executed will be returned.

Example:

const service = Piloted.service('my-service');

serviceHosts(name)

Returns an array of objects ({ address, port }) for the named service, representing all registered instances of the service.

Example:

const service = Piloted.serviceHosts('my-service');

Templating

Piloted will template your configuration file, similar to the way that ContainerPilot does. If you have an environment variable such as FOO=BAR then you can use {{.FOO}} in your configuration file and it will be substituted with BAR.

Events

Piloted implements the events interface. Specifically, if you need to know when the data has been updated, you can listen for the refresh event:

Piloted.on('refresh', function () {
  // update anything that needs to be done
});

A common use case is long-lived connections, e.g. database connections:

const service = Piloted.service('db');
 
// if service doesn't exist then there are no healthy instances in consul
const db = createDbConnection(service.address, services.port);
 
Piloted.on('refresh', () => {
  // update anything that needs to be done
  db.release();
  db.connect(service.address, service.port);
});