<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: HTTP Content Sensor

The HTTP Content sensor monitors a numerical value returned by an HTTP request. In the returned HTML page, each value must be placed between brackets [ ]. See the example below.

The sensor can show the following:

  • Returned numbers in dedicated channels, one channel for each value

icon-i-roundWhich channels the sensor actually shows might depend on the monitored device and the sensor setup.

HTTP Content Sensor

HTTP Content Sensor

Sensor in Other Languages

Dutch: HTTP (Inhoud), French: HTTP (contenu), German: HTTP (Inhalt), Japanese: HTTP コンテンツ, Portuguese: Conteúdo HTTP, Russian: HTTP: Содержимое, Simplified Chinese: HTTP 内容, Spanish: HTTP Contenido

Remarks

Limited to 50 Sensor Channels

icon-i-bluePRTG does not officially support more than 50 sensor channels. Depending on the data used with this sensor, you might exceed the maximum number of supported sensor channels. In this case, PRTG will try to display all sensor channels. Be aware, however, 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 in the Add Sensor dialog differ in comparison to the sensor's Settings tab.

HTTP Specific

Value Type

Define what kind of values your .html file gives back. Choose between:

  • Integer: An integer is expected as return value.
  • Float: A float is expected as return value, with a dot . between predecimal position and decimal places. The sensor will also display integer values unless they do not produce a buffer overflow.

icon-i-roundThe sensor cannot handle string values.

Number of Channels

Define how many values your .html file gives back. The sensor handles each value in its own sensor channel. Each value must be placed between brackets [ ]. Enter the number of bracket-value pairs that the URL will return. Enter an integer value.

icon-i-redDo not enter a number that is smaller than the number of values returned. Otherwise you will get an error message.

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 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.

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.

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

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.

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

Priority

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

Default Tags

httpsensor

HTTP Specific

Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value, the sensor will cancel the request and will show a corresponding error message. Enter an integer value. The maximum value is 900 seconds (15 minutes).

Script URL

Enter the URL the sensor connects to. It has to be URL encoded! If you enter an absolute URL, this address will be independent of the IP Address/DNS Name setting of the parent device.

icon-i-roundPRTG 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, see section Smart URL Replacement below.

Value Type

Shows the kind of values that the .html file returns. Once you have created a sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, please add the sensor anew.

icon-i-roundThis sensor implicitly supports SNI, an extension to the Transport Layer Security (TLS) protocol.

Advanced Sensor Data

Content Changes

Define what the sensor will do if the content of the monitored web page changes. Choose between:

  • Ignore changes: No action will be taken on change.
  • Trigger 'change' notification: The sensor will send an internal message indicating that the web page content has changed. In combination with a Change Trigger, you can use this mechanism to trigger a notification whenever the web page content changes.

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 (File name: Result of Sensor [ID].txt): Store the last result received from the sensor to the Logs (Sensors) subfolder of the PRTG data directory 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 overwrites these files with each scanning interval. icon-book-arrows
    For more information on how to find the folder used for storage, see section Data Storage.

icon-prtg-on-demandThis option is not available when the sensor runs on the Hosted Probe of a PRTG hosted by Paessler instance.

Authentication

Authentication

Define if authentication is necessary on the web page at the configured URL. Choose between:

  • No authentication needed
  • Web page needs authentication

User

This field is only visible if you enable Web page needs authentication above. Enter a username. Enter a string.

Password

This field is only visible if you enable Web page needs authentication above. Enter a password. Enter a string.

Authentication Method

This field is only visible if you enable Web page needs authentication above. Select the authentication method that the URL is protected with. Choose from:

  • Basic access authentication (HTTP): Use simple HTTP authentication. This is the default setting and is suitable for most cases.
    icon-i-round-redThis authentication method transmits credentials as plain text.
  • Windows NT LAN Manager (NTLM): Use the Microsoft NT LAN Manager (NTLM) protocol for authentication. This is sometimes used in intranets for single sign on (SSO).
  • Digest Access Authentication: Use digest access authentication. This applies a hash function to the password, which is safer than basic access authentication.

We recommend that you use the default value.

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

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

Graph Type

Define how different channels will be 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 will generate a 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 Channel Settings settings).

Stack Unit

This field is only visible if you enable Stack channels on top of each other above. Select 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 of the following settings are inherited from objects that are 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. For more information, see section Inheritance of Settings. To change a setting for this object only, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Proxy Settings for HTTP Sensors

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

The proxy settings determine how a sensor connects to a URL. You can enter data for an HTTP proxy server that sensors will use when connecting via HTTP or HTTPS.

icon-i-roundThis setting only affects monitoring and it determines the behavior of HTTP sensors. To change proxy settings for the core server, see section System Administration—Core & Probes.

icon-i-roundThe SSL Certificate sensor and the SSL Security Check sensor do not support HTTP proxies but you can configure connections via SOCKS proxies in the sensors' settings.

Name

Enter the IP address or Domain Name System (DNS) name of the proxy server. If you leave this field empty, no proxy will be used.

Port

Enter the port number of the proxy. Often, port 8080 is used. Enter an integer value.

User

If the proxy requires authentication, enter the username for the proxy login.

icon-i-round-redOnly basic authentication is available. Enter a string or leave the field empty.

Password

If the proxy requires authentication, enter the password for the proxy login.

icon-i-round-redOnly basic authentication is available. Enter a string or leave the field empty.

Scanning Interval

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours). The scanning interval determines the amount of time that 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 the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor will show a Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose from:

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

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

icon-i-roundIf you define error limits for a sensor's channels, the sensor will immediately show a Down status. No "wait" option will apply.

icon-i-roundIf a channel uses lookup values, the sensor will immediately show a Down status. No "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. 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 or hours) every week.

icon-book-arrowsYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing schedules, 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, the current sensor and all child objects will not be monitored. They will be in a Paused status 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 to a date in the past.

Maintenance Begins

This field 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 maintenance window.

Maintenance Ends

This field 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 maintenance window.

Dependency Type

Define a dependency type. You can use dependencies to pause monitoring for an object depending on the status of another object. You can choose from:

  • Use parent: Use the dependency type of the parent device.
  • Select a sensor: Use the dependency type of the parent device. Additionally, pause the current sensor if another specific sensor is in a Down status or in a Paused status caused by another dependency. Select below.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of its parent device: If the sensor is in a 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 is paused by another dependency.

icon-i-roundTo 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 will 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 you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current sensor will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects will be additionally delayed by the defined time span. This can help avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

icon-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 inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

User Group Access

Define the user groups that will have access to the selected object. 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 but it cannot be accessed.
  • 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 its settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit its 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.

icon-book-arrowsFor more details on access rights, see section User Access Rights.

Example

icon-speechFor example, consider the URL http://www.example.com/status.html that returns a PHP script with the current system status in a simple HTML page as follows:
 

<html>
 <body>
  Description: Script gives back current status of disk free (%) and CPU usage (%).
  [85.5][12.0]
 </body>
</html>

You would configure the HTTP Content sensor using

  • the script URL from above,
  • the value type Float,
  • and the number of channels 2.

The sensor calls the URL with every scanning interval and only regards the two values in brackets [ ] and handles each of them in one sensor channel. The additional description text and HTML tags are not necessary. In this example, they are added in case a human calls the URL.

icon-i-roundIf you define the number of channels as 1, the sensor will only read the first value. The second value will be ignored. Using 3 as the number of channels will result in a sensor error message.

Smart URL Replacement

Instead of entering a complete address in the URL field of an HTTP sensor, you can simply 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 will automatically fill 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, smart URL replacement makes it easy 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 will automatically create the URL https://www.example.com/
  • If you enter /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. It will be taken over by the device's DNS name and will be internally added, for example, http://:8080/

icon-i-round-redSmart URL replacement does not work for sensors that run on the probe device.

More

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

Knowledge Base: How can I monitor internal values of a web application with PRTG?

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

Edit Sensor Channels

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

Notification Triggers

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

Others

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

Sensor Settings Overview

For information about sensor settings, see the following sections:

Keywords: