JSON Path capability in a Webpage DataSource

I think the answer to this is gonna be “You need to script it, dummy”, but figured I’d check anyway...

I'm working on a new DataSource that pulls/interprets JSON data from a peudo-custom system via HTTP.

The system has a status page that lists the status of various components using JSON elements that have this general format:

ParameterName&ParameterType

Initial idea was that I could use the Webpage collector since it supports JSON/BSON parsing.

Issue I’m running into is that the values on most of these JSON elements are string (i.e. “true”/”false”).

I set up a DataPoint that can extract that value by putting in the JSON Path like so:

$.[##WILDVALUE##].[ParameterName&ParameterType]

...and I can see that I’m getting the “true”/”false” values back when I do a Poll Now. But - as we know - LM won’t deal with strings natively.

Workaround I came up with was to get length of the string since true/false are different lenghts.

According to sources online, JSON Path should support a calculation of string length.

I've also verified that I can do this by pasting my data and my JSON Path expression:

$.[ComponentName].[ParameterName&ParameterType].length

...into https://jsonpath.com/

In this parser, the .length function works as expected, and returns the length of the JSON value.

However, in LogicMonitor, I'm just getting this (example failure):

NAN after processing with json
(postProcessParam: $.[ComponentName].[ParameterName&ParameterType].length, reference=, useValue=body)

Anyone know if there is a way to make this JSON Path length function work?

marting

Posted 3 years ago·Last reply 3 years ago

3 comments

marting

OP3 years ago

Thanks for the input @Isaac Paramo and @Stuart Weenig. Going to give this a go in the near future.

LM User

·3 years ago

There’s an easier way than this:

function parseBooleanValue(value) {<br/>  if (value === 'true') {<br/>    return 1;<br/>  } else if (value === 'false') {<br/>    return 0;<br/>  } else {<br/>    return null; // or throw an error, depending on how you want to handle invalid values<br/>  }<br/>}

It uses the ternary operator:

(value == "true") ? 1 : 0

This is exactly equivalent to:

if (value == "true") {<br/>  return 1<br/>} else {<br/>  return 0<br/>}

No need for a function at all, it’s overkill.

Isaac Paramo

·3 years ago

Hi @marting --

I’m thinking you might actually need to script this to where you’re mapping the expected string values (true/false) to integer values, such as --

function parseBooleanValue(value) {<br/>  if (value === 'true') {<br/>    return 1;<br/>  } else if (value === 'false') {<br/>    return 0;<br/>  } else {<br/>    return null; // or throw an error, depending on how you want to handle invalid values<br/>  }<br/>}

Can’t fully vouch if this script will work specifically for you, but maybe something like this for some ideas --

// Define the URL of the JSON data source<br/>def url = "https://example.com/status.json"<br/><br/>// Define the JSON Path expressions to extract the data<br/>def expressions = [<br/>  "component1" : [<br/>    "param1&string" : "$.components[0].params[0].value",<br/>    "param2&bool" : "$.components[0].params[1].value"<br/>  ],<br/>  "component2" : [<br/>    "param1&string" : "$.components[1].params[0].value",<br/>    "param2&bool" : "$.components[1].params[1].value"<br/>  ]<br/>]<br/><br/>// Define a function to parse boolean values<br/>def parseBooleanValue(value) {<br/>  if (value === 'true') {<br/>    return 1;<br/>  } else if (value === 'false') {<br/>    return 0;<br/>  } else {<br/>    return null;<br/>  }<br/>}<br/><br/>// Define the main data collection function<br/>def collectData() {<br/>  // Fetch the JSON data from the URL<br/>  def response = get(url)<br/><br/>  // Parse the JSON data<br/>  def json = new JsonSlurper().parseText(response.text)<br/><br/>  // Loop through the components and parameters<br/>  for (componentName in expressions.keySet()) {<br/>    for (paramKey in expressions[componentName].keySet()) {<br/>      // Extract the value from the JSON data using the JSON Path expression<br/>      def value = JsonPath.read(json, expressions[componentName][paramKey])<br/><br/>      // Convert boolean values to integers<br/>      if (paramKey.endsWith("&bool")) {<br/>        value = parseBooleanValue(value)<br/>      }<br/><br/>      // Create a new datapoint with the value<br/>      def dpName = "${componentName}_${paramKey.replaceAll("&", "_")}"<br/>      def dp = new DataPoint(dpName, value)<br/>      addDataPoint(dp)<br/>    }<br/>  }<br/>}<br/><br/>// Call the main data collection function<br/>collectData()

In the above boilerplate, you would of course need to replace the url variable with the URL of your JSON data source and modify the expressions variable to match the structure of your JSON data source.

I hope this helps to stir some new ideas for you!