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.
For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.
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- This sensor supports the IPv6 protocol.
- This sensor has a very low performance impact.
- In a cluster, status changes triggered by limits only work on the master node.
- This sensor uses lookups to determine the status values of one or more channels. This means that possible states are defined in a lookup file. You can change the behavior of a channel by editing the lookup file that the channel uses. For details, see section Define Lookups.
- You can define credentials for REST API in settings that are higher in the object hierarchy, for example, in the settings of the parent device.
Requirement |
Description |
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Enabled Beta Sensors experimental feature |
This sensor requires that the Beta Sensors experimental feature of PRTG is enabled.
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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
Setting |
Description |
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Channel #2 - #10 |
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:
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Channel #x JSONPath/XPath |
Enter the JSONPath or XPath that you want to monitor. JSONPath example: $.sensorxref[0].totalsens
XPath example: /bookstore/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.
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Channel #x Custom Unit |
Enter the unit for the value that this sensor monitors. For example, #. |
Channel #x Type |
Select the value type that the channel displays:
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Click the Settings tab of a sensor to change its settings.
Setting |
Description |
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Sensor Name |
Enter a name to identify the sensor. |
Parent Tags |
Shows tags that the sensor inherits from its parent device, parent group, and parent probe.
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Tags |
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.
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 |
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 ( |
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.
Setting |
Description |
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Request URL |
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& XML REST API endpoint URL example: https://mycompany.com/api/table.xml?sortby=year |
Request Method |
Select the HTTP request method that the sensor uses to request the REST API:
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POST Body |
This setting is only visible if you select POST above. Enter the data part for the POST request. |
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.
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Timeout (Sec.) |
Enter a timeout in seconds for the request. Enter an integer value. The maximum timeout value is 900 seconds (15 minutes).
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Content Type |
Select the type of the content that the sensor queries. Choose between:
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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: $..prtg-version XPath example: /bookstore/book[1]/title |
Channel Settings
Setting |
Description |
---|---|
Channel #x JSONPath/XPath |
Enter the JSONPath or XPath that you want to monitor. JSONPath example: $.sensorxref[0].totalsens
XPath example: /bookstore/book[1]/year |
Channel #x Type |
Shows the value type that the channel displays.
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Channel #2 - #10 |
Shows if the channel is enabled or disabled.
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Setting |
Description |
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Primary Channel |
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.
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Graph Type |
Define how different channels are shown for this sensor:
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Stack Unit |
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. |
Setting |
Description |
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Result Handling |
Define what PRTG does with the sensor result:
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By default, all of the following 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.
Click to interrupt the inheritance.
Setting |
Description |
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Scanning Interval |
Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:
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If a Sensor Query Fails |
Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:
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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.
Setting |
Description |
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Schedule |
Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:
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Maintenance Window |
Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:
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Maintenance Begins |
This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the one-time maintenance window. |
Maintenance Ends |
This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window. |
Dependency Type |
Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:
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Dependency |
This setting is only visible if you enable Select a sensor above. Click |
Dependency Delay (Sec.) |
This setting is only visible if you select Select a sensor above. Define a time span in seconds for the dependency delay. After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.
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Click to interrupt the inheritance.
Setting |
Description |
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User Group Access |
Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:
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Click to interrupt the inheritance.
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.
Setting |
Description |
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Channel Unit Types |
For each type of channel, select the unit in which PRTG displays the data. If you define this setting on probe, group, or device level, you can inherit these settings to all sensors underneath. You can set units for the following channel types (if available):
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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.
To demonstrate the practical usage of JSONPath, we use this JSON example that a REST query might have returned as reference in this section. { |
Root |
The dollar sign ($) matches the root element of the JSON data. |
Child |
You can match a child with .<key> or [<key>]
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)"] |
Wildcard |
To match multiple values, you can use the asterisk symbol (*).
This expression matches 35985021 and 40085321 in the example above: $.devices[0].networks.*.rx_bytes |
Recursive Descent |
You can match all subitems of a node with two dots (..).
This expression matches 7229493 and 55294975 and 7229472 in the example above: $..tx_bytes |
Union |
You can match multiple children with [<key1>,<key2>,<...>].
This expression matches 35985021 and 7229493 in the example above: $.devices.0.networks.a["rx_bytes","tx_bytes"] |
Slice |
You can match multiple children of an array with [<begin>:<end>] or [<begin>:<end>:<step>].
This expression matches 63685865 in the example above: $.devices[-1:].networks.a.rx_bytes |
Current |
The @ symbol matches the current element.
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) |
Filter |
You can filter matches with [?<expression>].
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 |
Script |
You can modify matches with (<expression>) and keys with [<expression>].
This expression matches true and false in the example above because only the first device has a beta channel: $.devices[*](@.firmware.channel=="beta") |
Placeholder |
Placeholders give access to values of wildcards in a match. A placeholder #n (where n is a natural number) represents the value of the nth wildcard. You can use this in the keys of JSON arrays.
This expression creates a JSON map from ids to the corresponding firmware channel and matches {"0.7":"beta"} in the example above: {$.devices[#0].id:$.devices[*].channel}
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Constant |
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Operator |
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For more information about JSONPath, see JsonCons JSONPath.
For more information about XPath, see XPath Syntax.
Which channels the sensor actually shows might depend on the monitored 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 in percent. |
HTTP Status |
The HTTP status that the requested URL returns
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[Value] |
The values that a REST API returns in several channels
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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
For more information about sensor settings, see the following sections: