How to store correctly the probe's value to have trends and live value

[iCreil (Mirko)]

Hello Guys,
I need to find a way about how to store probes 's value over the time, but I don't know from where I can start, basically I've already read the guideline of elasticsearch and I cannot find a way to do that, I've even tried to find over internet tutorial about that. My idea is to send from a site periodically the probes's value with a POST request like that one:

POST /variables/temperature?pretty
{
  "id_site": "ID_site",
  "name":"Probe_01",
  "value":23.0,
  "measure":"°C",
  "description":"value proble 01",
  "timestamp":"2017-08-11T14:12:12"
}

I actually have just a node named "variables", in this node I have kind of variables that I specify on _type like for probe it's "temperature", anyway the problems is, that for every site I don't know the name of the probes and how many them are, so I want automatically get last value for each probe to show them on a map, then if I want a trend of that one I need just to search for name the probe and sort it by timestamp asc.

I want automatically get last value for each probe to show them on a map

I mean get all probes name on that site and give me no duplicate name, because right now on my node I have all the probes's value at every time so maybe I have something like that:

"hits": {
    "total": 12,
    "max_score": null,
    "hits": [
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49_s-93IfmC-JQNH9Z",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 23,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T17:00:00"
        },
        "sort": [
          1504285200000
        ]
      },
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49_wks3IfmC-JQNH9a",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 23.5,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T17:15:00"
        },
        "sort": [
          1504286100000
        ]
      },
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49_ze13IfmC-JQNH9b",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 23.7,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T17:30:00"
        },
        "sort": [
          1504287000000
        ]
      },
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49_4hc3IfmC-JQNH9c",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 24.2,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T17:45:00"
        },
        "sort": [
          1504287900000
        ]
      },
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49_7qV3IfmC-JQNH9d",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 24.4,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T18:00:00"
        },
        "sort": [
          1504288800000
        ]
      },
      {
        "_index": "variables",
        "_type": "temperature",
        "_id": "AV49__F93IfmC-JQNH9e",
        "_score": null,
        "_source": {
          "id_site": "RMTR001",
          "name": "SA1",
          "value": 24,
          "measure": "°C",
          "description": "sonda sala vendita",
          "timestamp": "2017-09-01T18:15:00"
        },
        "sort": [
          1504289700000
        ]
      }
}

and what really I want is just the la value of SA1 and SA2.

Finally, I have to read the last value update for each probe, but also I need to have a look at the trend of each probe. Can someone help me to build a better structure to store my data from the site, which is the best way to read them for last value and for a trend?

Thanks in advance,
Mirko