jsDelivr's load balancing algorithm
JavaScript CSS Other
Switch branches/tags
Nothing to show
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.

README.md

jsDelivr Openmix DNS application

Description

This is the live code that jsDelivr uses to do load balancing.

By default only MaxCDN and CloudFlare are considered for any requests. Set in array defaultProviders

But by using the countryMapping array we set overrides and change the default providers that the system will consider for different countries.

asnMapping sets ASN overides for monitoring tools because we collect Real User Metrics so the system does not work very well with synthetic tests originated from ISPs used by hosting providers

Validating the Code

The validate-js.sh script looks for possible errors in the application and test code. You must have Java installed for it to run. It executes both the Google Closure compiler and JSHint.

Here's an example where Google Closure compiler detects a misspelled property name, and JSLint detects that we forgot to comment-out a console print statement. We'd want to fix these issues before uploading the Openmix app.

$ ./validate-js.sh

Validating with Google Closure Compiler

app.js:171: WARNING - Property geo_default_on_marketasdf never defined on all_reasons
                    decision_reasons.push(all_reasons.geo_default_on_marketasdf);
                                          ^

0 error(s), 1 warning(s), 65.1% typed

Validating with JSHint

app.js: line 50, col 14, 'filter_object' is defined but never used.
app.js: line 69, col 14, 'filter_empty' is defined but never used.
app.js: line 80, col 14, 'get_lowest' is defined but never used.
app.js: line 42, col 45, 'response' is defined but never used.
app.js: line 42, col 36, 'request' is defined but never used.
app.js: line 70, col 18, 'key' is defined but never used.

6 errors

Running Unit Tests

Unit tests are a great way to make sure your application runs properly. Given an adequate understanding of the Openmix API, you can write tests to simulate most runtime conditions.

Unit tests are found in the test/tests.js file.

There are two different ways to execute the unit tests. The simplest is to open the test/test.html file in your browser (e.g. file:///path/to/test/test.html). Google Chrome works well for this. You can use the Chrome Developer Tools to debug any failed tests.

Another way to run the unit tests is on the command line using Karma Runner and PhantomJS. This requires that you have Node.js installed. It's a little more work to set up, but probably worthwhile in the long run if you anticipate writing a lot of Openmix code.

You can run the run-tests.sh script provided to execute the tests in Karma Runner. Here's an example:

$ ./run-tests.sh

Running Openmix application unit tests

INFO [karma]: Karma v0.10.10 server started at http://localhost:9876/
INFO [launcher]: Starting browser PhantomJS
INFO [PhantomJS 1.9.7 (Mac OS X)]: Connected on socket KHoK6W4HH8YDwj9EHCSk
LOG: Object{requireProvider: requireProvider}
LOG: Object{request: Object{getProbe: getProbe}, getProbe: getProbe, respond: respond, setTTL: setTTL, setReasonCode: setReasonCode}
LOG: Object{request: Object{getProbe: getProbe}, getProbe: getProbe, respond: respond, setTTL: setTTL, setReasonCode: setReasonCode}
...
PhantomJS 1.9.7 (Mac OS X): Executed 12 of 12 SUCCESS (0.075 secs / 0.017 secs)

All unit tests passed

Installing Node.js

Node.js is used by Karma Runner to run and execute your test code.

On Mac OS X

There are two good options for installing Node on Mac OS X. You can download an installer from nodejs.org. Or via Homebrew.

With Homebrew,

$ brew install node

On Linux (Ubuntu)

Installing Node.js on Ubuntu is simple, but requires an extra package that users sometimes miss:

$ sudo apt-get install nodejs nodejs-legacy

Installing JSHint and Karma

With Node.js installed you can use npm, the package manager for Node.js, to install JSHint, Karma Runner and other dependencies. The project directory contains a package.json file, which npm uses to download and install software locally.

From the directory containing package.json:

$ npm install