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 are still subject to change. Do not expect that all functions work properly, or that this sensor works as expected at all.
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 Aangepast v2
French: REST personnalisé v2
German: REST (Benutzerdefiniert) v2
Japanese: REST カスタム v2
Portuguese: REST (customizado) v2
Russian: Специальные настройки REST v2
Simplified Chinese: REST 自定义 v2
Spanish: REST (personalizado) v2
Remarks
Consider the following remarks and requirements for this sensor:
You can add this sensor to a multi-platform probe.
Known Issues
When you add more channels to the sensor, the fields Channel #x Unit and Channel #x Custom Unit remain visible regardless of what you select as Channel #x Value Type. You can ignore these fields if you select Status (string) or Lookup as Channel #x Value Type.
Limitations
Strings that contain angled brackets (< and >) cannot be mapped manually. This affects the following settings: Channel #x Strings mapped to the 'Up' status, Channel #x Strings mapped to the 'Warning' status, and Channel #x Strings mapped to the 'Down' status. We are already working on a solution.
Add Sensor
Setting
Description
Channel #2 - #10
You can define up to 10 channels. You must define at least one channel, so you see all available settings for Channel #1. Specify how to handle all other possible channels:
It is not possible to enable or disable channels after sensor creation.
Channel #x JSONPath/XPath
Enter the JSONPath or XPath of the JSON or XML result that you want to monitor.
JSONPath example:
$.store.book[0].year
XPath example:
/store/book[1]/year
Channel #x Name
Enter a name for the channel. Enter a string. For example, Total.
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?
Channel #x Unit
Enter the unit for the value that this sensor monitors. For example, #.
You can change this value later in the channel settings of this sensor.
Basic Sensor Settings
Basic Sensor Settings
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
rest
For more information about basic sensor settings, see section Sensor Settings.
REST Specific
REST Specific
Setting
Description
Request URL
Enter the URL of the JSON or XML REST API endpoint that you want to request.
You can use the following placeholders in this field: %restusername, %restpassword, %restbearertoken, %restplaceholder1, %restplaceholder2, %restplaceholder3, %restplaceholder4, and %restplaceholder5. You can define these placeholders in the credentials for REST API in settings that are higher in the object hierarchy.
PRTG uses a smart URL replacement with which you can use the parent device's IP address or Domain Name System (DNS) name setting as part of the URL. For more information, see section Smart URL Replacement.
If you enter 127.0.0.1 as IP address of the parent device, PRTG requests the following URL:
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.
POST Body
This setting is only visible if you select POST above.
Enter the data part for the POST request.
You can use the following placeholders in this field: %restusername, %restpassword, %restbearertoken, %restplaceholder1, %restplaceholder2, %restplaceholder3, %restplaceholder4, and %restplaceholder5. You can define these placeholders in the credentials for REST API in settings that are higher in the object hierarchy.
Custom Headers
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.
You can use the following placeholders in this field: %restusername, %restpassword, %restbearertoken, %restplaceholder1, %restplaceholder2, %restplaceholder3, %restplaceholder4, and %restplaceholder5. You can define these placeholders in the credentials for REST API in settings that are higher in the object hierarchy.
Timeout (Sec.)
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.
Content Type
Select the type of the content that the sensor queries:
JSON (default)
XML
Custom Sensor Message
Enter the JSONPath or XPath from which you want to receive a string that the sensor shows as the permanent sensor message.
JSONPath example:
$.store.book[0].title
XPath example:
/store/book[1]/title
Channel Settings
Channel Settings
Setting
Description
Channel #x JSONPath/XPath
Enter the JSONPath or XPath of the JSON or XML result that you want to monitor.
JSONPath example:
$.store.book[0].year
XPath example:
/store/book[1]/year
Channel #x Name
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?
Channel #x Value Type
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. If you select Absolute (float), the sensor automatically shows all decimal places of the received value in the channel. You can define how many decimal places of the channel's data that you want to display in graphs and tables in the channel settings.
Delta (counter): Counter values. The sensor calculates the difference between the last and the current value. Enter an integer. The sensor 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.
Status (string): The sensor shows a status depending on how you map the returned strings and shows the returned strings as sensor message.
Lookup: The sensors shows a status depending on how you define values in a custom lookup file.
Absolute (integer) and Absolute (float) support the extraction of numerical values from a received string. The sensor parses the numerical value from the beginning of the string until it encounters the first element that is not part of a numerical value, for example a letter. The sensor ignores whitespace characters.
You cannot change this value after sensor creation.
Channel #x Unit
This setting is only visible if you select Absolute (integer), Absolute (float), or Delta (counter) as Channel #x Value Type.
Select the unit that the channel displays:
Custom (default)
Percent
Percent (CPU)
Temperature (celsius)
Time (milliseconds)
Time (hours)
Time (seconds)
Bytes (memory)
Bytes (disk)
Bytes (file)
Bytes (bandwidth)
Bytes per second (disk)
Bytes per second (network)
You cannot change this value after sensor creation.
Channel #x Custom Unit
This setting is only visible if you select Custom (default) as Channel #x Unit.
Enter the custom unit of the value of this channel. Enter a string.
Channel #x Strings mapped to the 'Up' status
This setting is only visible if you select Status (string) as Channel #x Value Type.
Enter the strings that the sensor maps to the Up status in a comma-separated list.
If a string contains a comma, you must put the string in quotation marks. For example, to map the string Friday,2nd enter "Friday,2nd". If a string contains quotation marks, you must escape the quotation marks using a backslash (\) and put the string in quotation marks. For example, to map the string Friday "2nd" enter "Friday \"2nd\"".
Channel #x Strings mapped to the 'Warning' status
This setting is only visible if you select Status (string) as Channel #x Value Type.
Enter the strings that the sensor maps to the Warning status in a comma-separated list.
If a string contains a comma, you must put the string in quotation marks. For example, to map the string Friday,2nd enter "Friday,2nd". If a string contains quotation marks, you must escape the quotation marks using a backslash (\) and put the string in quotation marks. For example, to map the string Friday "2nd" enter "Friday \"2nd\"".
Channel #x Strings mapped to the 'Down' status
This setting is only visible if you select Status (string) as Channel #x Value Type.
Enter the strings that the sensor maps to the Down status in a comma-separated list.
If a string contains a comma, you must put the string in quotation marks. For example, to map the string Friday,2nd enter "Friday,2nd". If a string contains quotation marks, you must escape the quotation marks using a backslash (\) and put the string in quotation marks. For example, to map the string Friday "2nd" enter "Friday \"2nd\"".
Channel #x Handling of Unknown Strings
This setting is only visible if you select Status (string) as Channel #x Value Type.
Select the status to which the sensor maps all unknown strings in the returned result that are not manually mapped to the Up, the Warning, or the Down status:
'Up' status: Map all unknown strings to the Up status.
'Warning' status: Map all unknown strings to the Warning status.
'Down' status (default): Map all unknown strings to the Down status.
Channel #x Lookup ID
This setting is only visible if you select Lookup as Channel #x Value Type.
Enter the ID of the lookup you wish to use. You can find the ID in the ValueLookup parameter in the lookup file.
You cannot change this value after sensor creation.
Channel #2 - #10
You can define up to 10 channels. You must define at least one 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.
Sensor Display
Sensor Display
Setting
Description
Primary Channel
Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel 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.
Graph Type
Define how this sensor shows different channels:
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).
Stack Unit
This setting is only visible if you select Stack channels on top of each other above.
Select a unit from the list. PRTG stacks all channels with this unit 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.
Debug Options
Debug Options
Setting
Description
Result Handling
Define what PRTG does with the sensor result:
Discard result (default): 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 name is Result of Sensor [ID].log. This setting is for debugging purposes. PRTG overwrites this file 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.
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.
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 - jsonpath.com, 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.
Division of two integers. The expected result is an integer
2
2
/root/one div /root/two
eval($.root.one / $.root.two)
Division of two integers, the expected result is a floating-point number
0.5
0
n/a
eval($.root.one / $.root.two * 1.0)
Division of two integers with a floating point number as result
n/a
0.5
/root/one div /root/two_point5
eval($.root.one / $root.two_point5)
Division of a float and an integer
0.4
0.4
/root/one = /root/two
eval($.root.one == $.root.two)
If entries are equal
0 (false)
0 (false)
Smart URL Replacement
Instead of entering a complete address in the Request URL field of the REST Custom v2 sensor, you can only enter the protocol followed by a colon and three forward slashes (this means that you can enter either http:/// or https:///, or even a simple forward slash / as the equivalent for http:///). PRTG automatically fills in the parent device's IP Address/DNS Name in front of the third forward slash.
Whether this results in a valid URL or not depends on the IP address or Domain Name System (DNS) name of the parent device. In combination with cloning devices, you can use smart URL replacement to create many similar devices.
For example, if you create a device with the DNS name www.example.com and you add a REST Custom v2 sensor to it, you can provide values in the following ways:
If you enter https:/// in the Request URL field, PRTG automatically creates the URL https://www.example.com/
If you enter /help in the Request URL field, PRTG automatically creates the URL http://www.example.com/help
It is also possible to provide a port number in the Request URL field. It is taken over by the device's DNS name and is internally added, for example, https://:1616/
Smart URL replacement does not work for sensors that run on the probe device.
Channel List
Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.
Channel
Description
Downtime
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
HTTP Status
The HTTP status that the requested URL returns
Up status: Continue, Switching Protocols, Processing, OK, Created, Accepted, Non-Authoritative Information, No Content, Reset Content, Partial Content, Multi-Status, Already Reported, IM Used
Warning status: Multiple Choices, Moved Permanently, Found, See Other, Not Modified, Use Proxy, Switch Proxy (deprecated), Temporary Redirect, Permanent Redirect,
Down status: Bad Request, Unauthorized, Payment Required, Forbidden, Not Found, Method Not Allowed, Not Acceptable, Proxy Authentication Required, Request Time-out, Conflict, Gone, Length Required, Precondition Failed, Request Entity Too Large, Request URL Too Long, Unsupported Media Type, Requested Range Not Satisfiable, Expectation Failed, I'm a teapot, Policy Not Fulfilled, There are too many connections from your internet address, Unprocessable Entity, Locked, Failed Dependency, Unordered Collection, Upgrade Required, Precondition Required, Too Many Requests, Request Header Fields Too Large, No Response, The request should be retried after doing the appropriate action, Unavailable For Legal Reasons, Internal Server Error, Not Implemented, Bad Gateway, Service Unavailable, Gateway Time-out, HTTP Version not supported, Variant Also Negotiates[13], Insufficient Storage, Loop Detected, Bandwidth Limit Exceeded, Not Extended
Unknown status: Unknown
This channel is the primary channel by default.
[Value]
The values that a REST API returns in several channels