PRTG Manual: HTTP XML/REST Value Sensor

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

HTTP XML/REST Value Sensor

HTTP XML/REST Value Sensor

i_square_cyanFor a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

Sensor in Other Languages

  • Dutch: HTTP XML/REST Waarde
  • French: Valeur XML/REST (HTTP)
  • 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

Consider the following remarks and requirements for this sensor:

Remark

Description

Performance impact

This sensor has a high performance impact. We recommend that you use no more than 200 of this sensor on each probe.

.NET 4.7.2 or later

This sensor requires .NET 4.7.2 or later from Microsoft on the probe system. In a cluster, install it on every cluster node. If the sensor shows the error PE087, additionally install .NET 3.5 on the probe system.

i_round_redIf the framework is missing, you cannot create this sensor.

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

Windows Server

We recommend Windows Server 2016 on the probe system for best performance of this sensor.

SRP ciphers

This sensor does not support Secure Remote Password (SRP) ciphers.

Smart URL replacement

This sensor supports smart URL replacement.

IPv6

This sensor supports IPv6.

Single node

This sensor can monitor only one single node in an .xml file and shows the value in one channel. To monitor more than one node of an .xml document, add one sensor for each target node.

Knowledge Base

Add Sensor

Setting

Description

Channel Name

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

i_round_blueYou can change this value later in the channel settings of this sensor.

Basic Sensor Settings

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:

  • ptfsensor

i_square_cyanFor more information about basic sensor settings, see section Sensor Settings.

Sensor Settings

Sensor Settings

Sensor Settings

Setting

Description

URL

Enter the URL that returns the .xml file. If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device.

i_round_redThe URL must be URL encoded.

i_square_cyanPRTG 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.

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 and separate them with 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 more information about XPath, see the Knowledge Base: How can I use XPath with the HTTP XML/REST Value sensor?

HTTP User Name

If the URL requires authentication, enter the user name. 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 XML node. If this is a non-numeric 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 settings below.

Count XML Nodes

This setting is only visible if you select Use the number of occurrences of the selected XML node or its children/siblings 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.

Name Space Handling

Define whether to use namespaces in the .xml document or not:

  • Use name spaces: Process the value you enter in the XML Node (and optional property) field, possibly including namespace information.
  • Remove name spaces: 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

Define what to include in the header of the request that the sensor sends to the URL:

  • Enable (default): 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 select 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_redMake sure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.

Remove Characters

This setting is only visible if you select 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 select Use the value of the selected XML node above.

If the sensor value of the returned XML node is of the type float, you can define any character 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 if the channel value changes:

  • Ignore (default): Do nothing.
  • Trigger 'change' notification: Send an internal message that indicates a change.
    i_round_blueIn combination with a change trigger, you can use this to trigger a notification if a change occurs.

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

Unit String

Enter the unit for the values that this sensor returns. Enter a string.

i_round_bluePRTG uses the unit string for display purposes and shows it in graphs, data tables, and gauges.

i_round_blueYou can change this value later in the channel settings of this sensor.

Debug Options

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 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.

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

i_round_blueIn a cluster, PRTG stores the result in the PRTG data directory of the master node.

Sensor Display

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.

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 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.
    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 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.

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 b_inherited_enabled under the corresponding setting name to disable the inheritance and to display its options.

i_square_cyanFor more information, see section Inheritance of Settings.

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 (and optional property) field, the sensor processes the respective values:

Entry in Sensor's "XML Node (and optional property)" 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 might 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 name spaces (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 name spaces. 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/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.

Channel List

i_round_blueWhich 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

Execution Time

The execution time

[Value]

The value of one defined XML node

i_round_blueThis channel is the primary channel by default.

More

i_square_blueKNOWLEDGE BASE

Where can I find more information about the HTTP XML/REST Value sensor?

Which HTTP status code leads to which HTTP sensor status?

Which .NET version does PRTG require?

What security features does PRTG include?

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

How do I extract values from XML nodes (with nested tags) using 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?