PRTG Manual: HTTP XML/REST Value Sensor

The HTTP XML/REST Value sensor retrieves an .xml file from a URL and parses it.

The sensor can show the following:

  • Value of one defined XML node
HTTP XML/REST Value Sensor

HTTP XML/REST Value Sensor

Sensor in Other Languages

  • Dutch: HTTP XML/REST Waarde
  • French: Valeur HTTP XML/REST
  • German: HTTP XML-/REST-Wert
  • Japanese: HTTP XML/REST 値
  • Portuguese: Valor HTTP XML/REST
  • Russian: Значение HTTP XML/REST
  • Simplified Chinese: HTTP XML/REST 值
  • Spanish: Valor HTTP XML/REST

Remarks

  • This sensor can have a high impact on the performance of your monitoring system. Use it with care. We recommend that you use no more than 50 sensors of this sensor type on each probe.
  • This sensor requires .NET 4.7.2 or later on the probe system. If the sensor shows the error PE087, additionally install .NET 3.5 on the probe system.
  • This sensor does not officially support more than 50 channels. Depending on the data used with this sensor, you might exceed the maximum number of supported channels. In this case, PRTG tries to display all channels. Be aware, however, that you experience limited usability and performance.
  • This sensor does not support Secure Remote Password (SRP) ciphers.
  • This sensor supports smart URL replacement.
  • This sensor supports the IPv6 protocol.
  • This sensor has a high performance impact.

Detailed Requirements

Requirement

Description

.NET Framework

This sensor requires the Microsoft .NET Framework. .NET 4.7.2 or later must be installed on the probe system (on every cluster node, if on a cluster probe). If the framework is missing, you cannot create this sensor.

i_square_cyanFor more information, see the Knowledge Base: Which .NET version does PRTG require?

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

The following settings in the Add Sensor dialog differ in comparison to the sensor's Settings tab.

Sensor Settings

Setting

Description

Channel Name

Enter a name for the channel that displays the value at the URL.

Basic Sensor Settings

Click the Settings tab of a sensor to change its settings.

i_round_blueUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Setting

Description

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows tags that the sensor inherits from its parent device, parent group, and parent probe. This setting is shown for your information only and cannot be changed here.

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.

i_round_blueIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:

  • ptfsensor

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 (i_priority_1) to the highest priority (i_priority_5).

Sensor Settings

Setting

Description

URL

Enter the URL that returns the .xml file.

i_round_redThe URL must be URL encoded.

If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device. PRTG uses a smart URL replacement that lets you use the parent device's IP address/DNS name setting as part of the URL.

i_square_cyanFor more information, see section Smart URL Replacement.

XML Node (and optional property)

Enter the name of the node that this sensor checks, or enter a node name and a property name to check a property value. To obtain a value from nested tags, enter the tag names separated by a forward slash (/), for example, use myTag/myTagInside as XML node value.

i_round_blueYou can also check values in JavaScript Object Notation (JSON). See section Checking JSON.

i_round_blueYou can try to use XPath syntax here but it does not work in all cases and we do not provide any technical support for XPath issues. For further documentation about XPath, see the Knowledge Base: How can I use XPath with the HTTP XML/REST Value Sensor?

HTTP Username

If the URL requires authentication, enter the username. Enter a string or leave the field empty.

HTTP Password

If the URL requires authentication, enter the password. Enter a string or leave the field empty.

Sensor Value

Define what value the sensor shows:

  • Use the value of the selected XML node: Return the value that the sensor finds at the specified XML node. If this is a non-numerical value, the sensor shows 0.
  • Use the number of occurrences of the selected XML node or its children/siblings: Return the number of occurrences found. Define further below.

Count XML Nodes

This setting is only visible if you enable the return number option above. Define which count the sensor shows:

  • Occurrences of the selected XML node: Return how often the defined XML node occurs at the URL.
  • Child nodes of the selected XML node: Return the number of child nodes that exist below the node at the URL.
  • Sibling nodes of the selected XML node: Return the number of sibling nodes that exist next to the node at the URL.

Namespaces

Define whether namespaces in the .xml document are used or not:

  • Use namespaces: Process the value you enter in the XML Node (and optional property) field, possibly including namespace information.
  • Remove namespaces: Ignore namespace information in the .xml document and process the value you enter in the XML Node (and optional property) field as node names only.

i_square_cyanFor more information see section About Namespaces.

Content Type in Header

Define what to include in the header of the request sent to the URL:

  • Enable (recommended): This works for most web servers and is the recommended setting.
  • Disable: Only very few web servers cannot handle this content type and need this setting. Try this if you get an error message with the enabled option.
  • Custom: You can use a custom content type.

Custom Content Type

This setting is only visible if you enable Custom above. Enter a custom content type like text/xml or text/html.

HTTP Headers

Optionally enter a list of custom HTTP headers with their respective values that you want to transmit to the URL. The syntax of a list with header-value pairs is header1:value1|header2:value2|...|headerx:valuex

i_round_blueThe sensor does not accept header field names that include a dash () character. If you want to use such an HTTP header, leave out the dash in the name. For example, enter ContentType:value instead of Content-Type:value. Example: From:[email protected]|AcceptLanguage:en-us

i_round_redEnsure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.

Characters to Remove

This setting is only visible if you enable Use the value of the selected XML node above. Optionally enter a string that the sensor removes from the returned XML value.

Use this to remove any unwanted characters from the result, for example to remove a thousands separator from numeric values. Enter a string or leave the field empty.

Decimal Delimiter

This setting is only visible if you enable Use the value of the selected XML node above. If the sensor value of the selected XML node is of the type float, you can define any character here, which is then handled as the decimal delimiter. Enter one character or leave the field empty.

Custom Message

Optionally enter a custom sensor message. Use %1 as a placeholder to automatically fill in the returned XML value. Enter a string or leave the field empty.

If Channel Value Changes

Define what the sensor does when the sensor value changes:

  • Ignore changes (default): Take no action on change.
  • Trigger 'change' notification: Send an internal message indicating that the sensor value has changed. In combination with a change trigger, you can use this mechanism to trigger a notification whenever the sensor value changes.

i_round_redThe notification for this sensor can only be triggered if the returned value is a numerical value. This option does not support strings.

Unit String

Enter the unit for the values that this sensor returns. Enter a string. PRTG uses the unit string for display purposes and shows it in graphs, data tables, and gauges.

i_round_blueIf you want to change the unit after sensor creation, you can change it in the sensor's channel settings.

Debug Options

Setting

Description

Sensor Result

Define what PRTG does with the sensor results:

  • Discard sensor result: Do not store the sensor result.
  • Write sensor result to disk (file names: Result of Sensor [ID].*): Store the last result received from the sensor to the \Logs\sensors subfolder of the PRTG data directory on the probe system (master node, if in a cluster). File names: Result of Sensor [ID].* and Result of Sensor [ID].Data.*. This is for debugging purposes. PRTG overwrites these files with each scanning interval.

i_podThis option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.

Sensor Display

Setting

Description

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.

i_round_blueYou can set a different primary channel later by clicking b_channel_primary below a channel gauge on the sensor's Overview tab.

Graph Type

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.
    i_round_redYou 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 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.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should change them centrally in the root group settings if necessary. To change a setting for this object only, click b_inherited_enabled under the corresponding setting name to disable the inheritance. You then see the options described below.

i_square_cyanFor more information, see section Inheritance of Settings.

Scanning Interval

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

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:

  • 30 seconds
  • 60 seconds
  • 5 minutes
  • 10 minutes
  • 15 minutes
  • 30 minutes
  • 1 hour
  • 4 hours
  • 6 hours
  • 12 hours
  • 1 day

i_round_blueYou can change the available intervals in the system administration on PRTG on premises installations.

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:

  • Set sensor to down immediately: Set the sensor to the Down status immediately after the first request fails.
  • Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status.
  • Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails.
  • Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails.
  • Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails.
  • Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails.

i_round_blueSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show the Down status. It is not possible to immediately set a WMI sensor to the Down status, so the first option does not apply to these sensors. All other options can apply.

i_round_blueIf you define error limits for a sensor's channels, the sensor immediately shows the Down status. None of the interval options apply.

i_round_blueIf a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Schedules, Dependencies, and Maintenance Window

i_round_blueYou 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

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:

  • None
  • Saturdays
  • Sundays
  • Weekdays
  • Weekdays Eight-To-Eight (08:00 - 20:00)
  • Weekdays Nights (17:00 - 09:00)
  • Weekdays Nights (20:00 - 08:00)
  • Weekdays Nine-To-Five (09:00 - 17:00)
  • Weekends

i_square_cyanYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Schedules.

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:

  • Not set (monitor continuously): Do not set up a one-time maintenance window. Monitoring is always active.
  • Set up a one-time maintenance window: Set up a one-time maintenance window and pause monitoring. You can define a time span for a the pause below.

i_round_blueTo terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

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:

  • Use parent: Use the dependency type of the parent object.
  • Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in the Down status or in the Paused status because of another dependency.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in the Down status, the device is paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor is paused if the parent group is paused by another dependency.

i_round_blueTo test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This setting is only visible if you enable Select a sensor above. Click b_search_light and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This setting is only visible if you enable 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.

i_round_redThis setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

Access Rights

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

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:

  • Inherited: Inherit the access rights settings of the parent object.
  • No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
  • Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
  • Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
  • Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

i_square_cyanFor more details on access rights, see section Access Rights Management.

Channel Unit Configuration

Click b_inherited_enabled to interrupt the inheritance.

Setting

Description

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, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):

  • Bandwidth
  • Memory
  • Disk
  • File
  • Custom

i_round_blueCustom channel types are only available on sensor level.

Checking JSON

With the XML Node (and optional property) field, you can also check values that are returned in JSON notation under the defined URL.

i_speechExample

A JSON notated section might look like the following:

{
 "test": "Hello World",
 "object": {
   "value": "content",
   "AnotherValue": "AnotherContent"
 },
 "arraytest": [
   "one",
   "two"
 ]
}

Depending on your entries in the XML Node field, the sensor processes the respective values:

Entry in Sensor's "XML Node" Field (from Example Above)

Processed Value (from Example Above)

test

Hello World

object/value

content

object/AnotherValue

AnotherContent

object

contentAnotherContent

arraytest[1]

one

arraytest[2]

two

i_round_redThe sensor converts whitespaces in JSON keys into underscores (_). So, for example, if you look for the node some node in the JSON, you need to enter some_node into the node field. If you count the number of nodes (for example, some_node), both some node and some_node would be counted if they appear in the JSON.

i_round_blueIf a key exists more than once in the JSON, the value of the first appearance is returned (no difference between whitespace and underscore).

About Namespaces

In an .xml document, tags may use namespaces.

i_speechExample

A namespace notated section might look like the following:

<myNamespace:myNode>
 some information
</myNamespace:myNode>

If you set this sensor to Use namespaces (this is the default setting), it expects the full node name, including the namespace information, in the XML Node (and optional property) field. In the example above, this is myNamespace:myNode.

If your node names are unique even without the namespace information, you can simplify the settings by setting this sensor to Remove namespaces. The sensor then expects the node name only in the XML Node (and optional property) field. In the example above, this is myNode.

Smart URL Replacement

Instead of entering a complete address in the URL field of an HTTP 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 or 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 an HTTP sensor to it, you can provide values in the following ways:

  • If you enter https:/// in the URL field, PRTG automatically creates the URL https://www.example.com/
  • If you enter /help in the URL field, PRTG automatically creates and monitor the URL http://www.example.com/help
  • It is also possible to provide a port number in the URL field. It is taken over by the device's DNS name and is internally added, for example, http://:8080/

i_round_redSmart URL replacement does not work for sensors that run on the probe device.

More

i_square_blueKNOWLEDGE BASE

Which HTTP status code leads to which HTTP sensor status?

Is there a tool available that can help me build queries for the HTTP XML/REST Value sensor?

How do I extract values from XML nodes (with nested tags) using the HTTP XML/REST Value Sensor?

How can I use XPath with the HTTP XML/REST Value Sensor?

Why does my HTTP XML/REST Value sensor return a 404 error?

My HTTP sensors don't work. What can I do?

For which sensor types do you recommend Windows Server 2012 R2 or later and why?

Which .NET version does PRTG require?

Sensor Settings Overview

For more information about sensor settings, see the following sections: