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V3 Release (#60)
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* dns errors now get passed
* Filtering UP instances by default. Added tests.
* Adding unit tests for startHeartbeats and startRegistryFetches
* improved error reporting
* added changelog message
* added event support
* improved the logic regarding waiting for registries
* added better exception handling for malformed configuration files
* adding tests for DNS error cases and fixing an uncaught exception
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@jquatier
jquatier committed May 9, 2016
1 parent 84ac4ec commit b95da7a
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5 changes: 5 additions & 0 deletions CHANGES.md
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@@ -0,0 +1,5 @@
## 3.0.0
- Added better exception handling around malformed YAML configuration files.
- Added support for the following events: `started`, `registered`, `deregistered`, `heartbeat`, and `registryUpdated`.
- Improved the stability of the client when it encounters downstream DNS errors, as a side-effect the callback for `fetchRegistries()` now returns errors when they are encountered.
- Populate registry cache with instances that have a status of `UP`, `filterUpInstances` can be set to `false` to disable.
25 changes: 25 additions & 0 deletions README.md
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Expand Up @@ -123,6 +123,31 @@ If your have multiple availability zones and your DNS entries set up according t

This will cause the client to perform a DNS lookup using `config.eureka.host` 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.servicePath` | `/eureka/v2/apps/` | path to eureka REST service
`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](#looking-up-eureka-servers-in-aws-using-dns)
`eureka.fetchMetadata` | `true` | fetch AWS metadata when in AWS environment, see [Configuring for AWS environments](#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

Expand Down
92 changes: 68 additions & 24 deletions src/EurekaClient.js
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Expand Up @@ -5,6 +5,7 @@ import merge from 'deepmerge';
import path from 'path';
import dns from 'dns';
import { series } from 'async';
import { EventEmitter } from 'events';

import AwsMetadata from './AwsMetadata';
import Logger from './Logger';
Expand All @@ -18,19 +19,32 @@ function noop() {}
for reporting instance health.
*/

function fileExists(file) {
try {
return fs.statSync(file);
} catch (e) {
return false;
}
}

function getYaml(file) {
let yml = {};
if (!fileExists(file)) {
return yml; // no configuration file
}
try {
yml = yaml.safeLoad(fs.readFileSync(file, 'utf8'));
} catch (e) {
// Ignore YAML load error.
// configuration file exists but was malformed
throw new Error(`Error loading YAML configuration file: ${file} ${e}`);
}
return yml;
}

export default class Eureka {
export default class Eureka extends EventEmitter {

constructor(config = {}) {
super();
// Allow passing in a custom logger:
this.logger = config.logger || new Logger();

Expand Down Expand Up @@ -91,10 +105,11 @@ export default class Eureka {
Build the base Eureka server URL + path
*/
buildEurekaUrl(callback = noop) {
this.lookupCurrentEurekaHost(eurekaHost => {
this.lookupCurrentEurekaHost((err, eurekaHost) => {
if (err) return callback(err);
const { port, servicePath, ssl } = this.config.eureka;
const host = ssl ? 'https' : 'http';
callback(`${host}://${eurekaHost}:${port}${servicePath}`);
callback(null, `${host}://${eurekaHost}:${port}${servicePath}`);
});
}

Expand Down Expand Up @@ -131,7 +146,11 @@ export default class Eureka {
done();
}
},
], callback);
], (err, ...rest) => {
if (err) this.logger.warn('Error starting the Eureka Client', err);
this.emit('started');
callback(err, ...rest);
});
}

/*
Expand Down Expand Up @@ -168,10 +187,11 @@ export default class Eureka {
this.config.instance.status = 'UP';
const connectionTimeout = setTimeout(() => {
this.logger.warn('It looks like it\'s taking a while to register with ' +
'Eureka. This usually means there is an issue connecting to the host ' +
'specified. Start application with NODE_DEBUG=request for more logging.');
'Eureka. This usually means there is an issue connecting to the host ' +
'specified. Start application with NODE_DEBUG=request for more logging.');
}, 10000);
this.buildEurekaUrl(eurekaUrl => {
this.buildEurekaUrl((err, eurekaUrl) => {
if (err) return callback(err);
request.post({
url: eurekaUrl + this.config.instance.app,
json: true,
Expand All @@ -184,8 +204,10 @@ export default class Eureka {
'registered with eureka: ',
`${this.config.instance.app}/${this.instanceId}`
);
this.emit('registered');
return callback(null);
} else if (error) {
this.logger.warn('Error registering with eureka client.', error);
return callback(error);
}
return callback(
Expand All @@ -199,7 +221,8 @@ export default class Eureka {
De-registers with the Eureka server and stops heartbeats.
*/
deregister(callback = noop) {
this.buildEurekaUrl(eurekaUrl => {
this.buildEurekaUrl((err, eurekaUrl) => {
if (err) return callback(err);
request.del({
url: `${eurekaUrl}${this.config.instance.app}/${this.instanceId}`,
gzip: true,
Expand All @@ -209,8 +232,10 @@ export default class Eureka {
'de-registered with eureka: ',
`${this.config.instance.app}/${this.instanceId}`
);
this.emit('deregistered');
return callback(null);
} else if (error) {
this.logger.warn('Error deregistering with eureka', error);
return callback(error);
}
return callback(
Expand All @@ -231,13 +256,18 @@ export default class Eureka {
}

renew() {
this.buildEurekaUrl(eurekaUrl => {
this.buildEurekaUrl((err, eurekaUrl) => {
if (err) {
this.logger.warn('eureka heartbeat FAILED, will retry', err);
return;
}
request.put({
url: `${eurekaUrl}${this.config.instance.app}/${this.instanceId}`,
gzip: true,
}, (error, response, body) => {
if (!error && response.statusCode === 200) {
this.logger.debug('eureka heartbeat success');
this.emit('heartbeat');
} else if (!error && response.statusCode === 404) {
this.logger.warn('eureka heartbeat FAILED, Re-registering app');
this.register();
Expand All @@ -260,7 +290,9 @@ export default class Eureka {
*/
startRegistryFetches() {
this.registryFetch = setInterval(() => {
this.fetchRegistry();
this.fetchRegistry(err => {
if (err) this.logger.warn('Error fetching registries', err);
});
}, this.config.eureka.registryFetchInterval);
}

Expand Down Expand Up @@ -296,7 +328,8 @@ export default class Eureka {
Retrieves all applications registered with the Eureka server
*/
fetchRegistry(callback = noop) {
this.buildEurekaUrl(eurekaUrl => {
this.buildEurekaUrl((err, eurekaUrl) => {
if (err) return callback(err);
request.get({
url: eurekaUrl,
headers: {
Expand All @@ -307,8 +340,10 @@ export default class Eureka {
if (!error && response.statusCode === 200) {
this.logger.debug('retrieved registry successfully');
this.transformRegistry(JSON.parse(body));
this.emit('registryUpdated');
return callback(null);
} else if (error) {
this.logger.warn('Error fetching registry', error);
return callback(error);
}
callback(new Error('Unable to retrieve registry from Eureka server'));
Expand Down Expand Up @@ -340,19 +375,27 @@ export default class Eureka {

/*
Transforms the given application and places in client cache. If an application
has a single instance, the instance is placed into the cache as an array of one
has a single instance, the instance is placed into the cache as an array of one
*/
transformApp(app, cache) {
if (app.instance.length) {
cache.app[app.name.toUpperCase()] = app.instance;
cache.vip[app.instance[0].vipAddress] = app.instance;
} else {
const instances = app.instance.filter((instance) => (this.validateInstance(instance)));
cache.app[app.name.toUpperCase()] = instances;
cache.vip[app.instance[0].vipAddress] = instances;
} else if (this.validateInstance(app.instance)) {
const instances = [app.instance];
cache.vip[app.instance.vipAddress] = instances;
cache.app[app.name.toUpperCase()] = instances;
}
}

/*
Returns true if instance filtering is disabled, or if the instance is UP
*/
validateInstance(instance) {
return (!this.config.eureka.filterUpInstances || instance.status === 'UP');
}

/*
Fetches the metadata using the built-in client and updates the instance
configuration with the hostname and IP address. If the value of the config
Expand Down Expand Up @@ -401,9 +444,9 @@ export default class Eureka {
*/
lookupCurrentEurekaHost(callback = noop) {
if (this.amazonDataCenter && this.config.eureka.useDns) {
this.locateEurekaHostUsingDns(resolvedHost => callback(resolvedHost));
this.locateEurekaHostUsingDns((err, resolvedHost) => callback(err, resolvedHost));
} else {
return callback(this.config.eureka.host);
return callback(null, this.config.eureka.host);
}
}

Expand All @@ -417,24 +460,25 @@ export default class Eureka {
locateEurekaHostUsingDns(callback = noop) {
const { ec2Region, host } = this.config.eureka;
if (!ec2Region) {
throw new Error(
return callback(new Error(
'EC2 region was undefined. ' +
'config.eureka.ec2Region must be set to resolve Eureka using DNS records.'
);
));
}
dns.resolveTxt(`txt.${ec2Region}.${host}`, (err, addresses) => {
if (err) {
throw new Error(
return callback(new Error(
`Error resolving eureka server list for region [${ec2Region}] using DNS: [${err}]`
);
));
}
const random = Math.floor(Math.random() * addresses[0].length);
dns.resolveTxt(`txt.${addresses[0][random]}`, (resolveErr, results) => {
if (resolveErr) {
throw new Error(`Error locating eureka server using DNS: [${resolveErr}]`);
this.logger.warn('Failed to locate DNS record for Eureka', resolveErr);
callback(new Error(`Error locating eureka server using DNS: [${resolveErr}]`));
}
this.logger.debug('Found Eureka Server @ ', results);
callback([].concat(...results).shift());
callback(null, [].concat(...results).shift());
});
});
}
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1 change: 1 addition & 0 deletions src/defaultConfig.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ export default {
heartbeatInterval: 30000,
registryFetchInterval: 30000,
fetchRegistry: true,
filterUpInstances: true,
servicePath: '/eureka/v2/apps/',
ssl: false,
useDns: false,
Expand Down
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