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Aurelio, System Admin at Paessler AG

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

  • It can show the value of one defined XML node.
HTTP XML/REST Value SensorHTTP XML/REST Value Sensor

Click here to enlarge: http://media.paessler.com/prtg-screenshots/http_xmlrest_value.png

Remarks

  • Requires .NET 4.0 or higher on the probe system. If the sensor shows the error PE087, please additionally install .NET 3.5 on the probe system.
  • This sensor can monitor only one single node in an XML file and shows the value in one channel. If you need to monitor more than one node of an XML document, please add the sensor for each target node anew.
  • Supports Smart URL Replacement.
  • We recommend Windows 2012 R2 on the probe system for best performance of this sensor.
  • Knowledge Base: HTTP XML/REST Value Sensor: FAQ
  • Knowledge Base: Which HTTP status code leads to which HTTP sensor status?
  • This sensor type does not support Secure Remote Password (SRP) ciphers.
  • This sensor type can have a high impact on the performance of your monitoring system. Please use it with care! We recommend that you use no more than 50 sensors of this sensor type on each probe.

Requirement: .NET Framework

icon-toolsThis sensor type requires the Microsoft .NET Framework to be installed on the computer running the PRTG probe, either on the local system (on every node, if on a cluster probe), or on the system running the remote probe. If the framework is missing, you cannot create this sensor.

Required .NET version (with latest updates): .NET 4.0 (Client Profile is sufficient), .NET 4.5, or .NET 4.6.

icon-book-bulbFor more information, please see this Knowledge Base article: https://kb.paessler.com/en/topic/60543

Limited to 50 Sensor Channels

icon-i-bluePRTG does not support more than 50 sensor channels officially. Depending on the data used with this sensor type, you might exceed the maximum number of supported sensor channels. In this case, PRTG will try to display all sensor channels. However, please be aware that you will experience limited usability and performance.

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 will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

The following settings for this sensor differ in the Add Sensor dialog in comparison to the sensor's settings page.

Sensor Settings

Channel Name

Enter a name for the channel that will display the value at the given URL.

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

icon-i-roundUsually, a sensor connects to the IP Address or DNS Name of the parent device where you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. Please see below for details on available settings.

Basic Sensor Settings

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

Tags

Enter one or more Tags , separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags .

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Sensor Settings

URL

Enter the URL that returns the XML file. It has to be URL encoded ! If you enter an absolute URL, the sensor uses this address independently from the IP Address/DNS Name setting of the device on which you create this sensor.

PRTG uses a smart URL replacement that allows you to use the parent device's IP address/DNS name setting as part of the URL. For more information, please see section Smart URL Replacement below.

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 slash symbol, for example, use myTag/myTagInside as XML node value.

icon-i-roundYou can also check values in JavaScript Object Notation (JSON) notation. Please see Checking JSON section below.
 

icon-i-roundYou can try using 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, please see More section below.

HTTP Username

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

HTTP Password

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

Sensor Value

Define what value this sensor shows. Choose between:

  • Use the value of the selected XML node : Return the value that the sensor finds at the specified XML node. If this is non-numeric, 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. Choose between:

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

Namespaces

Define whether namespaces in the XML document are used or not. Choose between:

  • Use Namespaces : Process the value you enter in the XML Node (and optional property) field including possibly existing 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.

For more information see About Namespaces section below.

Content Type in Header

Define what to include in the header of the request sent to the URL defined above. Choose between:

  • 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 field is only visible when you enable the Custom option above. Enter a custom content type like text/xml or text/html .

HTTP Headers

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

icon-i-blueThe sensor does not accept header field names that include a dash () character. If you want to use such an HTTP header, please leave out the dash of the name. For example, enter ContentType:value instead of Content-Type:value .

Example: From:[email protected]|AcceptLanguage:en-us

icon-i-redEnsure that the HTTP header statement is valid! Otherwise, the sensor request will not be successful.

Characters to Remove

This field is only visible if you enable the Use the value of the selected XML node option 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, a thousands separator from numeric values. Please enter a string or leave the field empty.

Decimal Delimiter

This setting is only visible if you enable the Use the value of the selected XML node option above. If the sensor value of the selected XML node is of the type float , you can define any character here which is 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. Please enter a string or leave the field empty.

SSLv3 Connection

Define if you want to allow SSLv3 only for connections to the URL configured above. Choose between:

  • Use SSLv3 if available
  • Force usage of SSLv3

icon-i-round-redThe force method does not work when the requested URL uses forward secrecy . For details, see this Knowledge Base article: My HTTP sensors could not create an SSL secure channel and are down. What can I do?

If Channel Value Changes

Define what this sensor will do when the sensor value changes. You can choose between:

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

icon-i-round-redThe change notification for this sensor can only be triggered if the returned value is a numerical value. Strings are not supported by this option and cannot trigger a notification.

Unit String

Enter a string that the sensor will add to the retrieved values as a unit description. This is for display purposes only.

Debug Options

Sensor Result

Define what PRTG will do with the sensor results. Choose between:

  • Discard sensor result : Do not store the sensor result.
  • Write sensor result to disk (Filename: "Result of Sensor [ID].txt") : Store the last result received from the sensor to the Logs (Sensor) directory in the PRTG data folder on the probe system the sensor is running on (on the Master node if in a cluster). File names: Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt . This is for debugging purposes. PRTG overrides these files with each scanning interval.
    icon-book-arrowsFor more information on how to find the folder used for storage, see section Data Storage .
     

icon-prtg-on-demandYou cannot access stored logs of sensors that run on the local probe of PRTG on demand.

Sensor Display

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 will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

icon-i-roundYou can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default) : Show an own 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 will generate an easy-to-read graph that visualizes the different components of your total traffic.
    icon-i-roundThis option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be 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 following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings. To change a setting only for this object, disable inheritance by clicking the check mark in front of the corresponding setting name. You will then see the options described below.

Scanning Interval

Scanning Interval

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that a sensor has time reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Down status. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

  • Set sensor to "down" immediately : The sensor will show an error immediately after the first failed request.
  • Set sensor to "warning" for 1 interval, then set to "down" (recommended) : After the first failed request, the sensor will show a yellow warning status. If the following request also fails, the sensor will show an error.
  • Set sensor to "warning" for 2 intervals, then set to "down" : Show an error status only after three continuously failed requests.
  • Set sensor to "warning" for 3 intervals, then set to "down" : Show an error status only after four continuously failed requests.
  • Set sensor to "warning" for 4 intervals, then set to "down" : Show an error status only after five continuously failed requests.
  • Set sensor to "warning" for 5 intervals, then set to "down" : Show an error status only after six continuously failed requests.

icon-i-roundSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to "down" immediately, so the first option will not apply to these sensor types. All other options can apply.

icon-i-roundIf a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.
 

icon-i-roundIf a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundInheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a "maintenance window" period, this object and all child objects will not be monitored. They will be in a paused state instead. Choose between:

  • Not set (monitor continuously) : No maintenance window will be set and monitoring will always be active.
  • Set up a one-time maintenance window : Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

icon-i-roundTo terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

  • Use parent : Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.
  • Select object : Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.
  • Master object for parent : Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be 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 will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

icon-i-roundTesting your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

icon-i-round-redThis setting is not available if you choose this sensor to Use parent or to be the Master object for parent . In this case, please define delays in the parent Device Settings or in the superior Group Settings .

Access Rights

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown: It contains all user groups from your setup. For each user group you can choose from the following access rights:

  • Inherited : Use the access rights settings of the parent object.
  • None : Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
  • Read : Users in this group can see the object and review its monitoring results.
  • Write : Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
  • Full : Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

For more details on access rights, please see the section User Access Rights .

Channel Unit Configuration

Channel Unit Types

For each type of sensor channel, define the unit in which data is displayed. If defined 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

icon-i-roundCustom channel types can be set on sensor level only.

Checking JSON

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

Example

A JSON notated section may 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 will process 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

icon-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.

icon-i-roundIf 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.

Example

A namespace notated section may look like the following:

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

 

If you set this sensor to Use Namespaces (this is the default setting), it will expect the full node name, including the namespace information, in the XML Node (and optional property) field. In the example above, this would be 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 will then expect the node name only in the XML Node (and optional property) field. In the example above, this would be myNode .

Smart URL Replacement

Instead of entering a complete address in the URL field of an HTTP sensor, you can merely enter the protocol followed by colon and three slashes (that means you can enter either http:/// or https:/// or even a simple slash / as equivalent for http:/// ). PRTG will then fill in the parent device's IP address or DNS name in front of the third slash automatically. Whether this results in a valid URL or not, depends on the IP address or DNS name of the device where this HTTP sensor is created on. In combination with cloning devices, the smart URL replacement makes it easy to create many like devices.

For example, if you create a device with DNS name www.example.com and you put an HTTP sensor on it, you can provide values the following ways:

  • Providing the value https:/// in the URL field, PRTG will automatically create the URL https://www.example.com/ from that.
  • Using the value /help in the URL field, PRTG will automatically create and monitor the URL http://www.example.com/help
  • It is also possible to provide a port number in the URL field which will be taken over by the device's DNS name and internally added, for example, http://:8080/

icon-i-round-redSmart URL replacement does not work for sensors running on the Probe Device .

More

Knowledge Base: Which HTTP status code leads to which HTTP sensor status?

Knowledge Base: Is there a tool available that can help me building queries for the XML/Rest Sensor?

Knowledge Base: How do I extract values from XML nodes (with nested tags) using PRTG's XML/Rest Value Sensor?

Knowledge Base: How can I use XPath with PRTG's XML/Rest Value Sensor?

Knowledge Base: HTTP XML/REST Value Sensor shows protocol violation. What can I do?

Knowledge Base: Why does my HTTP XML/REST Value Sensor return a 404 error?

Knowledge Base: My HTTP sensors could not create an SSL secure channel and are down. What can I do?

Knowledge Base: For which sensor types do you recommend Windows Server 2012 R2 and why?

Knowledge Base: Which .NET version does PRTG require?

Edit Sensor Channels

To change display settings, spike filter, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, please see the Sensor Channels Settings section.

Notifications

Click the Notifications tab to change notification triggers. For detailed information, please see the Sensor Notifications Settings section.

Others

For more general information about settings, please see the Object Settings section.

Sensor Settings Overview

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