eureka-client

A JavaScript implementation of a client for Eureka (https://github.com/Netflix/eureka), the Netflix OSS service registry.

Usage

First, install the module into your node project:

npm install eureka-client --save

Add Eureka client to a Node application.

The Eureka module exports a JavaScript function that can be constructed.

import Eureka from 'eureka-client';

// Or, if you're not using a transpiler:
const Eureka = require('eureka-client').Eureka;

// example configuration
const client = new Eureka({
  // application instance information
  instance: {
    app: 'some-service',
    hostName: 'localhost',
    ipAddr: '127.0.0.1',
    port: 8080,
    vipAddress: 'test.something.com',
    dataCenterInfo: {
      name: 'MyOwn',
    },
  },
  eureka: {
    serviceUrl: [
      'http://192.168.99.100:8761/eureka/v2/apps/',
      'http://192.168.99.100:32768/eureka/v2/apps/'
    ]
  },
});

The Eureka client searches for the YAML file eureka-client.yml in the current working directory. It further searches for environment specific overrides in the environment specific YAML files (e.g. eureka-client-test.yml). The environment is typically development or production, and is determined by the NODE_ENV environment variable. The options passed to the constructor overwrite any values that are set in configuration files.

You can configure a custom directory to load the configuration files from by specifying a cwd option in the object passed to the Eureka constructor.

const client = new Eureka({
  cwd: `${__dirname}/config`,
});

If you wish, you can also overwrite the name of the file that is loaded with the filename property. You can mix the cwd and filename options.

const client = new Eureka({
  filename: 'eureka',
  cwd: `${__dirname}/config`,
});

Register with Eureka & start application heartbeats

client.start();

De-register with Eureka & stop application heartbeats

client.stop();

Get Instances By App ID

// appInfo.application.instance contains array of instances
const appInfo = client.getInstancesByAppId('YOURSERVICE');

Get Instances By Vip Address

// appInfo.application.instance contains array of instances
const appInfo = client.getInstancesByVipAddress('YOURSERVICEVIP');

Configuring for AWS environments

For AWS environments (dataCenterInfo.name == 'Amazon') the client has built-in logic to request the AWS metadata that the Eureka server requires. See Eureka REST schema for more information.

// example configuration for AWS
const client = new Eureka({
  // application instance information
  instance: {
    app: 'some-service',
    port: 8080,
    vipAddress: 'test.something.com',
    statusPageUrl: 'http://__HOST__:8080/',
    healthCheckUrl: 'http://__HOST__:8077/healthcheck',
    dataCenterInfo: {
      name: 'Amazon',
    },
  },
  eureka: {
    // eureka server host / port / EC2 region
    host: 'eureka.test.mydomain.com',
    port: 80,
  },
});

Notes:

• Under this configuration, the instance hostName and ipAddr will be set to the public host and public IP that the AWS metadata provides.
• For status and healthcheck URLs, you may use the replacement key of __HOST__ to use the public host.
• Metadata fetching can be disabled by setting config.eureka.fetchMetadata to false if you want to provide your own metadata in AWS environments.

Looking up Eureka Servers in AWS using DNS

If your have multiple availability zones and your DNS entries set up according to the Wiki article Configuring Eureka in AWS Cloud, you'll want to set config.eureka.useDns to true and set config.eureka.ec2Region to the current region (usually this can be pulled into your application via an environment variable, or passed in directly at startup).

This will cause the client to perform a DNS lookup using the host of the currently selected server in config.eureka.serviceUrl and config.eureka.ec2Region. The naming convention for the DNS TXT records required for this to function is also described in the Wiki article above.

Configuration Options

option | default value | description ---- | --- | --- logger | console logging | logger implementation for the client to use eureka.heartbeatInterval | 30000 | milliseconds to wait between heartbeats eureka.registryFetchInterval | 30000 | milliseconds to wait between registry fetches eureka.fetchRegistry | true | enable/disable registry fetching eureka.filterUpInstances | true | enable/disable filtering of instances with status === UP eureka.ssl | false | enable SSL communication with Eureka server eureka.useDns | false | look up Eureka server using DNS, see Looking up Eureka Servers in AWS using DNS eureka.fetchMetadata | true | fetch AWS metadata when in AWS environment, see Configuring for AWS environments eureka.useLocalMetadata | false | use local IP and local hostname from metadata when in an AWS environment.

Events

Eureka client is an instance of EventEmitter and provides the following events for consumption:

event | data provided | description ---- | --- | --- started | N/A | Fired when eureka client is fully registered and all registries have been updated. registered | N/A | Fired when the eureka client is registered with eureka. deregistered | N/A | Fired when the eureka client is deregistered with eureka. heartbeat | N/A | Fired when the eureka client has successfully renewed it's lease with eureka. registryUpdated | N/A | Fired when the eureka client has successfully update it's registries.

Debugging

The library uses request for all service calls, and debugging can be turned on by passing NODE_DEBUG=request when you start node. This allows you you double-check the URL being called as well as other request properties.

NODE_DEBUG=request node example.js

You can also turn on debugging within the library by setting the log level to debug:

client.logger.level('debug');

Known Issues

400 Bad Request Errors from Eureka Server

Later versions of Eureka require a slightly different JSON POST body on registration. If you are seeing 400 errors on registration it's probably an issue with your configuration and it could be the formatting differences below. The history behind this is unclear and there's a discussion here. The main differences are:

• port is now an object with 2 required fields $ and @enabled.
• dataCenterInfo has an @class property.

See below for an example:

const client = new Eureka({
  // application instance information
  instance: {
    app: 'jqservice',
    hostName: 'localhost',
    ipAddr: '127.0.0.1',
    port: {
      '$': 8080,
      '@enabled': true,
    },
    vipAddress: 'jq.test.something.com',
    dataCenterInfo: {
      '@class': 'com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo',
      name: 'MyOwn',
    },
  },
  eureka: {
    // eureka server host / port
    serviceUrl: [ 'http://192.168.99.100:32768/eureka/v2/apps/' ],
  },
});

404 Not Found Errors from Eureka Server

This probably means that the Eureka REST service is located on a different path in your environment. The default is http://<EUREKA_HOST>/eureka/v2/apps, but depending on your setup you may need to set eureka.servicePath in your configuration to another path. The REST service could be hung under /eureka/apps/ or possibly /apps/.

Usage with Spring Cloud

If you are using Spring Cloud you'll likely need the following settings:

• Set the path of the serviceUrl to /eureka/apps/.
• Use the newer style of the configuration here or Spring Cloud Eureka will throw a 500 error.
• Put single quotes around boolean @enabled. Unfortunately, a 500 error regarding parsing seems to occur without that.

Below is an example configuration that should work with Spring Cloud Eureka server:

const client = new Eureka({
  instance: {
    app: 'jqservice',
    hostName: 'localhost',
    ipAddr: '127.0.0.1',
    statusPageUrl: 'http://localhost:8080',
    port: {
      '$': 8080,
      '@enabled': 'true',
    },
    vipAddress: 'jq.test.something.com',
    dataCenterInfo: {
      '@class': 'com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo',
      name: 'MyOwn',
    },
  },
  eureka: {
    serviceUrl: [ 'http://192.168.99.100:32768/eureka/apps/' ],
  },
});

Tests

The test for the module are written using mocha and chai. To run the unit tests, you can use the gulp test task:

gulp test

If you wish to have the tests watch the src/ and test/ directories for changes, you can use the test:watch gulp task:

gulp test:watch