<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: REST Custom v2 Sensor
The REST Custom v2 sensor queries a JavaScript Object Notation (JSON) or Extensible Markup Language (XML) Representational State Transfer (REST) application programming interface (API) endpoint and maps the JSON or XML result to sensor values.
This sensor is in beta status. The operating methods and the available settings can change at any time. Do not expect that all functions work properly, or that this sensor works as expected at all. Be aware that this sensor can be removed from PRTG at any time.
REST Custom v2 Sensor
For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.
Sensor in Other Languages
- Dutch: REST Custom v2
- French: REST Custom v2
- German: REST Custom v2
- Japanese: REST Custom v2
- Portuguese: REST Custom v2
- Russian: REST Custom v2
- Simplified Chinese: REST Custom v2
- Spanish: REST Custom v2
Remarks
Detailed Requirements
Add Sensor
The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the settings that are required to create the sensor. You can change nearly all settings on the sensor's Settings tab after creation.
Channel Settings
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Channel #2 - #10
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You can define up to 10 channels. You must define at least one data channel, so you see all available settings for Channel #1. Specify how to handle all other possible channels:
- Disable: Do not create this channel.
- Enable: Create this channel.
It is not possible to enable or disable channels after sensor creation.
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Channel #x JSONPath/XPath
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Enter the JSONPath or XPath that you want to monitor.
JSONPath example:
$.sensorxref[0].totalsens
If the JSONPath points to a boolean, the sensor translates TRUE as 1 and FALSE as 0.
XPath example:
/bookstore/book[1]/year
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Channel #x Name
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Enter a name for the channel.. Enter a string. For example, Total. PRTG dynamically generates channels with this name as the identifier.
If the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?
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Channel #x Custom Unit
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Enter the unit for the value that this sensor monitors. For example, #.
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Channel #x Type
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Select the value type that the channel displays:
- Absolute (integer): Integer64 values with or without an operational sign, such as 10 or 120 or -12 or 120.
- Absolute (float): Double values, such as -5.80 or 8.23.
- Delta (counter): Counter values. PRTG calculates the difference between the last and the current value. Enter an integer. PRTG additionally divides the delta value by a time period to indicate a speed value.
This mode only works if the difference between the last and the current value is positive and increases with each scanning interval. This mode does not support negative values and decreasing values.
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Basic Sensor Settings
Click the Settings tab of a sensor to change its settings.
Basic Sensor Settings
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Sensor Name
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Enter a name to identify the sensor.
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Parent Tags
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Shows tags that the sensor inherits from its parent device, parent group, and parent probe.
This setting is for your information only. You cannot change it.
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Tags
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Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.
It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).
For performance reasons, it can take some minutes until you can filter for new tags that you added.
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
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Priority
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Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority () to the highest priority ().
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Usually, a sensor connects to the IP Address/DNS Name of the parent device. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings.
REST Specific
REST Specific
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Request URL
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Enter the URL of the JSON or XML REST API endpoint that you want to request.
JSON REST API endpoint URL example:
https://mycompany.com/api/table.json?id=1&passhash=<passhash>&username=<username>&content=sensorxref&
noraw=1&filter_basetype=probe&columns=totalsens=textraw,upsens=textraw,
downsens=textraw,partialdownsens=textraw,warnsens=textraw,pausedsens=textraw,
unusualsens=textraw,undefinedsens=textraw,downacksens=textraw
XML REST API endpoint URL example:
https://mycompany.com/api/table.xml?sortby=year
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Request Method
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Select the HTTP request method that the sensor uses to request the REST API:
- GET (default): Use the GET method to request the REST API.
- POST: Use the POST method to request the REST API.
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POST Body
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This setting is only visible if you select POST above. Enter the data part for the POST request.
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Custom Headers
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Enter a list of custom HTTP headers with their respective values that you want to transmit to the target URL. The syntax of a header-value pair is header1:value1.
If you enter more than one header-value pair, enter each pair in one line:
header1:value1
header2:value2
header3:value3
Make sure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.
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Timeout (Sec.)
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Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).
If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.
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Content Type
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Select the type of the content that the sensor queries. Choose between:
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Custom Sensor Message
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Enter the JSONPath or XPath from which you want to receive a string that the sensor shows as the permanent sensor message.
JSONPath example:
$..prtg-version
XPath example:
/bookstore/book[1]/title
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Channel Settings
Channel Settings
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Channel #x JSONPath/XPath
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Enter the JSONPath or XPath that you want to monitor.
JSONPath example:
$.sensorxref[0].totalsens
If the JSONPath points to a boolean, the sensor translates TRUE as 1 and FALSE as 0.
XPath example:
/bookstore/book[1]/year
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Channel #x Type
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Shows the value type that the channel displays.
PRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.
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Channel #2 - #10
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Shows if the channel is enabled or disabled.
It is not possible to enable or disable channels after sensor creation.
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Sensor Display
Sensor Display
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Primary Channel
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Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.
You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.
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Graph Type
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Define how different channels are shown for this sensor:
- Show channels independently (default): Show a graph for each channel.
- Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).
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Stack Unit
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This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.
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Debug Options
Debug Options
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Result Handling
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Define what PRTG does with the sensor result:
- Discard result: Do not store the sensor result.
- Store result: Store the last sensor result in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This setting is for debugging purposes. PRTG overwrites these files with each scanning interval.
This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.
In a cluster, PRTG stores the result in the PRTG data directory of the master node.
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Inherited Settings
By default, all of these settings are inherited from objects that are higher in the hierarchy. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance and to display its options.
For more information, see section Inheritance of Settings.
Scanning Interval
Scanning Interval
For more information, see section Root Group Settings, section Scanning Interval.
Schedules, Dependencies, and Maintenance Window
You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.
Schedules, Dependencies, and Maintenance Window
For more information, see section Root Group Settings, section Schedules, Dependencies, and Maintenance Window.
Access Rights
Access Rights
For more information, see section Root Group Settings, section Access Rights.
Channel Unit Configuration
Which channel units are available depends on the sensor type and the available parameters. If no configurable channels are available, this field shows No configurable channels.
Channel Unit Configuration
For more information, see section Root Group Settings, section Channel Unit Configuration.
JSONPath
The REST Custom v2 sensor uses JSONPath to assign values from the returned JSON to channels. With JSONPath, you provide the path to the value in the JSON source that you want to monitor in a channel.
The JSONPath implementation that PRTG uses for the REST Custom v2 sensor might differ from other JSONPath implementations. To test simple JSONPath expressions and calculations, you can use JSONPath Online Evaluator, for example. Note that this tool might not work properly with complex JSONPath expressions that PRTG supports.
Example
To demonstrate the practical usage of JSONPath, we use this JSON example that a REST query might have returned as reference in this section.
{
"devices":[
{
"firmware":{
"id":"0.7",
"date":"2017-05-18T17:11:43.7049944Z",
"channel": "beta"
},
"networks": {
"a": {
"rx_bytes": 35985021,
"rx_packets": 176791,
"rx_errors": 0,
"rx_dropped": 476,
"tx_bytes": 7229493,
"tx_packets": 35518,
"tx_errors": 0,
"tx_dropped": 1
},
"b": {
"rx_bytes": 40085321,
"tx_bytes": 55294975
}
}
},
{
"networks": {
"a": {
"rx_bytes": 63685865,
"tx_bytes": 7229472
}
}
}
]
}
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Root
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The dollar sign ($) matches the root element of the JSON data.
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Child
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You can match a child with .<key> or [<key>]
- .<key> must only contain letters, numbers, and underscore (_). Hyphens (-) are not supported.
- [<key>] must only contain a number or a quoted string.
Example
This expression matches 35985021 in the example above:
$.devices.0.networks.a.rx_bytes
You get the same result with this expression:
$["devices"][0]["networks"]["a"]["rx_bytes"]
If an element contains a hyphen (-), the .<key> notation does not work. Use the [<key>] notation in this case:
$["data"][0]["system-stats"]["temps"]["Board (CPU)"]
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Wildcard
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To match multiple values, you can use the asterisk symbol (*).
Example
This expression matches 35985021 and 40085321 in the example above:
$.devices[0].networks.*.rx_bytes
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Recursive Descent
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You can match all subitems of a node with two dots (..).
Example
This expression matches 7229493 and 55294975 and 7229472 in the example above:
$..tx_bytes
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Union
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You can match multiple children with [<key1>,<key2>,<...>].
Example
This expression matches 35985021 and 7229493 in the example above:
$.devices.0.networks.a["rx_bytes","tx_bytes"]
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Slice
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You can match multiple children of an array with [<begin>:<end>] or [<begin>:<end>:<step>].
- By default, begin, end, and step are either integers or empty.
- The default approach is to go step by step from the first array element to the last element.
- Step can also be a negative integer to go through the array in reversed order.
Example
This expression matches 63685865 in the example above:
$.devices[-1:].networks.a.rx_bytes
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Current
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The @ symbol matches the current element.
Example
This expression matches 40.085321 and 55.294975 in the example above and can be used to receive a percentage value:
$.devices[1].networks.a.["rx_bytes","tx_bytes"](@/100000000*100)
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Filter
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You can filter matches with [?<expression>].
Example
This expression matches 35985021 in the example above because the first device is the only one with a beta channel:
$.devices[?(@.firmware.channel=="beta")].networks.a.rx_bytes
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Script
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You can modify matches with (<expression>) and keys with [<expression>].
Example
This expression matches true and false in the example above because only the first device has a beta channel:
$.devices[*](@.firmware.channel=="beta")
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Placeholder
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Placeholders give access to values of wildcards in a match. A placeholder #n (where n is a natural number) represents the value of the nth wildcard. You can use this in the keys of JSON arrays.
Example
This expression creates a JSON map from ids to the corresponding firmware channel and matches {"0.7":"beta"} in the example above:
{$.devices[#0].id:$.devices[*].channel}
This is an extension of the official JSONPath.
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Constant
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- Numeric constants as 64-bit floating point: 12345.678
- String constants with double quotes: "switch"
- Boolean constants: true and false
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Operator
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- Parentheses control the order of evaluation: (<expression>)
- Arrays with brackets: [<expression>, <expression>, ...]
- Objects: {<expression>:<expression>, <expression>:<expression>, ...}
- Conditionals: <condition> ? <expression> : <expression>
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For more information about JSONPath, see JsonCons JSONPath.
REST Custom v2 Sensor: XPath
For more information about XPath, see XPath Syntax.
Channel List
Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.
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Downtime
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In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status in percent.
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HTTP Status
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The HTTP status that the requested URL returns
This channel is the primary channel by default.
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[Value]
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The values that a REST API returns in several channels
For details about the return value format, see section Custom Sensors.
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More
PRTG MANUAL
Knowledge Base
What are beta sensors and how can I use them?
What security features does PRTG include?
Can I create a sensor to monitor the number of paused or unknown sensors?
MISCELLANEOUS
Paessler JSONPath
Paessler Gval
JSONPath Online Evaluator