Basic Use Cases

1. Main Structure.
2. Use Cases.

Main Structure

In fact, a Custom Answer Configuration structure does not have any strict rules. Below, we just describe the recommended structure, that, in our opinion, is the best one for a Custom Answer Script. So feel free to use your own approach, experiment and invent.

A typical Custom Answer has three 'sections':

// configuration
const configuration = {
    ...
};
// functions
const someFunction = () => ... ;
...
function anotherFunction() {
...
};
...
// onRequest
function onRequest(req: IRequest, res: IResponse) {
   ...
};

• configuration - here you place a configuration object, it can define providers with some properties, useful sets of data, default properties etc. For example:

const configuration = {
    providers: [
        {
            providerName: ('belugacdn' as TCDNProvider), // CDN Provider alias
            cname: 'www.foo.com', // cname to pick as a result
            padding: 0, //  additional bonus or penalty
            countries: (['UA'] as TCountry[]) // countries to apply additional rules
        },
        {
            providerName: ('ovh-cdn' as TCDNProvider),
            cname: 'www.bar.com', // in most cases it is your Answer
            padding: 0,
            continents: (['NA', 'EU'] as TContinent[]) // to apply additional rules
        },
        {
            providerName: ('cloudflare' as TCDNProvider),
            cname: 'www.baz.com',
            padding: 0,
            asns: [12345, 54321] // ASN Numbers to apply additional rules
        },
        {
            providerName: ('fastly'  as TCDNProvider),
            cname: 'www.foo-bar.com',
            padding: 0,
            except_countries: (['CN'] as TCountry[]) // Exception for rules
        },
        {
            providerName: ('some-expensive-cdn'  as TCDNProvider), // example!
            cname: 'www.expensiveanswer.com',
            padding: 100, // the penalty - will show what is it for below
            except_countries: (['CN'] as TCountry[]) // Exception for rules
        },
        ...
        {
            providerName: ('does-not-exist'  as TCDNProvider)
            whatever: 'some value', // 
            you: ['Y','O','U'],
            want_to_have: 1000,
            here: { here: 'now' }
        }
    ],
    defaultTtl: 20, // The DNS TTL to be applied to DNS responses in seconds.
    geoDefault: false,
    asnOverride: false, // Set to `true` to enable the asn override feature
    defaultProvider: ('fastly' as TCDNProvider),
    ...
    nyNiceProperty: 'anything'
    ...
}

• functions - if you need additional funcs- that is the right place to put those:

/**
 * Pick index of lowest number in array of numbers
 */
const getLowest = (array: number[]): number => array.indexOf(Math.min(...array));
...

• onRequest - The Main Custom Answers function we operate with.

function onRequest(req: IRequest, res: IResponse) {
    let resultAnswer;
    // Logic goes here
    ...
    // Prepare response
    res.setCNAMERecord(resultAnswer ? resultAnswer : defaultAnswer);
    res.setTTL(defaultTtl);
    return;
}

As we have mentioned, feel free to implement your own structure and solutions. The only the must is onRequest(req: IRequest, res: IResponse) (Main function) usage.

Use Cases

Case 1.1: Provider Availability with Weights.

The Case: A customer uses 2+ CDN providers. A user is directed to the CDN that is available at a given point in time. If both CDNs are available the decision is based on weight. Go to the Use Case

Case 1.2: Availability based on Monitor Uptime.

The Case: A customer uses 2+ nodes, monitored by PerfOps Monitoring Feature. A user is directed to the node that has the best Monitor Uptime at a given point in time. If both Monitors are down returns random answer. Go to the Use Case

Case 2.1: Balancing based on the CDN with the better Performance

The Case: A customer uses 2+ CDN providers. Their user is simply balanced to the better performing one. Go to the Use Case

Case 3.1: Geolocation with excluded country

The Case: User has different providers for 2 regions - using 1 CDN for the USA and another CDN for the rest of the world. Go to the Use Case

Case 3.2: The specific answer for the specific region

The Case: User has different CDN provider for each continent, we need to set corresponding answer or fallback if continent is not determined. Go to the Use Case

Case 3.3 Pick the best performance provider for user country

The Case: One of the most popular cases: select the CDN with the best performance for visitor's country.. Go to the Use Case

Case 4.1: Using country-based answers from remote sources

The Case: A customer keeps his answers-for-countries information as JSON at some remote source, wants to retrieve it and use for balancing. Go to the Use Case

More Use Cases coming soon!

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