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How can I get the REST Customer Sensor to monitor the number of nodes returned?

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Hi,

I want PRTG to monitor an API (via a GET) and have a channel plot the number of results returned, so I can track licensing restrictions.

So when I run the query on day 1, the JSON returned would be like:

[ { "id": "1001", "value": "Lorem" }, { "id": "1002", "value": "ipsum" } ]

And the value plotted in the Channel should be 2.

On day 2, the JSON returned would be:

[ { "id": "1001", "value": "Lorem" }, { "id": "1002", "value": "ipsum" }, { "id": "1003", "value": "dolor" } ]

And the value plotted in the Channel should be 3.

I tried doing a node count with the HTTP XML/REST Value, but according to https://kb.paessler.com/en/topic/32703-parse-json-array it is unable to parse valid JSON arrays.

I imagine this would have something to do with a REST configuration file, but I'm not sure how to do counts in that.

channel rest rest-custom

Created on Dec 19, 2017 4:43:22 AM by Jamie Imms (0) ●1



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Dear Jamie,

Thank you for the KB-Post. Which exact sensor are you using here? Bear in mind, values have to be numerical for PRTG. It cannot use string results.

best regards.

Created on Dec 19, 2017 1:33:54 PM by Torsten Lindner [Paessler Support]



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Hi Torsten, I am using the REST Custom Sensor

Created on Dec 20, 2017 12:32:21 AM by Jamie Imms (0) ●1

Last change on Dec 21, 2017 10:22:58 AM by Luciano Lingnau [Paessler]



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Hello Jamie,
thank you for your reply.

According to the responsible developer this is doable with something like the following template:

{
  "prtg": {
    "description" : {
      "device": "rest_test",
      "query": "https://jsonplaceholder.typicode.com/todos.json",
      "comment": "Demo Demo"
    },
    "result": [
     {
          "channel": "Total count" ,
          "value": len($.*),
          "unit": "Count"
    }
    ]
  }
}
len()returns the count of entries and he just have to use the root element with $.* for all elements

For a complete list of functions that can be used in the sensor please refer to:

Best Regards,
Luciano Lingnau [Paessler Support]

Created on Dec 21, 2017 10:26:21 AM by Luciano Lingnau [Paessler]



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