Probes selection rules

[zarianec]

Current measurement request payload:

{
    "locations": [
        {
            "type": "country",
            "value": "FR",
            "limit": 3 // per-location limit
        },
        {
            "type": "country",
            "value": "PL",
            "limit": 4 // per-location limit
        }
    ],
    "measurement": {
        "type": "ping",
        "target": "hello.com",
        "packets": 3
    },
    "limit": 10 // global limit
}

Global limit and per-location limit are mutually exclusive - it means that if the global limit is present in the request, the per-location limit is not allowed and vice-versa.

Because we are not limited by a single location type per request - the resulting probes set must contain unique records only.

const probes = [
	{ id: 1, country: "PL", contient: "EU" },
	{ id: 2, country: "UA", contient: "EU" },
	{ id: 3, country: "PL", contient: "EU" },
	{ id: 4, country: "NL", contient: "EU" },
];

const request = [
	{ type: "country": value: "PL", limit: 1 },
	{ type: "continent": value: "EU", limit: 4 },
]

const result = [
	// because of request[0]
	{ id: 3, country: "PL", contient: "EU" },
	

	// because of request[1] - even though 4 probes from the EU was requested - only 3 was found
	{ id: 2, country: "UA", contient: "EU" }, 
	{ id: 4, country: "NL", contient: "EU" },
	{ id: 1, country: "PL", contient: "EU" },
]

Case 1. With locations and limit per location

This is the easiest one. We must find the exact amount of probes for each location. If we don't have enough probes for a specific location, only these we have will be used and the final probes count may be smaller than expected.

Example:
Probes: UA:10; PL:4; NL:3
Request: UA:5; PL: 7; NL:3
Result: UA:5; PL:4; NL:3

Case 2. With locations and global limit

The final amount of probes shouldn't exit the global limit. It may be smaller if we don't have enough probes in total though.
At least 1 probe from each requested location must be present in the results (if we have probes there at all ofc.).
If some locations don't have enough probes the result must be filled with probes from locations that have them.

Example:
Probes: UA:6; PL:2; NL:1
Request: UA; PL; NL - Limit: 6
Result: UA:3; PL:2; NL:1

Case 3. Without locations and global a limit (e.g. World Wide)

For World Wide (WW) requests, we must apply "smart" logic where we break the world into groups and the final probes set must contain a predefined percentage of probes from each group.

percentage	location
5	Africa
15	Asia
30	Europe
10	Oceania
30	North America
10	South America

Example:
For a WW request with a global limit of 100, the result will contain 30 probes from Europe, 15 from Asia, etc.