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.

The sensor can show the following:

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

i_round_blueWhich 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: Contenido HTTP

Remarks

  • 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 medium performance impact.

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.

HTTP Specific

Setting

Description

Value Type

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

  • 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 also displays integer values unless they do not produce a buffer overflow.

i_round_blueThe 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 channel. Each value must be placed between brackets [ ]. Enter the number of bracket-value pairs that the URL returns. Enter an integer value.

i_round_redDo not enter a number that is smaller than the number of values returned. Otherwise you get an error message.

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:

  • httpsensor

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).

HTTP Specific

Setting

Description

Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value, the sensor cancels the request and shows 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 is independent of the IP Address/DNS Name setting of the parent device.

i_round_bluePRTG uses a smart URL replacement that lets you use the parent device's IP Address/DNS Name setting as part of the URL. For more information, see section Smart URL Replacement.

Value Type

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

i_round_blueThis sensor implicitly supports SNI, an extension to the Transport Layer Security (TLS) protocol.

Advanced Sensor Data

Setting

Description

Content Changes

Define what the sensor does if the content of the monitored web page changes:

  • Ignore changes: No action is taken on change.
  • Trigger 'change' notification: The sensor sends 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 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.

Authentication

Setting

Description

Authentication

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

  • No authentication needed
  • Web page needs authentication

User

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

Password

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

Authentication Method

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

  • Basic access authentication (HTTP): Use simple HTTP authentication. We recommend that you use this option.
    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.

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.

Proxy Settings for HTTP Sensors

Click b_inherited_enabled to interrupt the inheritance.

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

i_round_blueThis setting only applies to HTTP sensors and how they monitor. To change the proxy settings for the PRTG core server, see section Core & Probes.

Setting

Description

Name

Enter the IP address or Domain Name System (DNS) name of the proxy server. If you leave this field empty, HTTP sensors do not use a proxy.

Port

Enter the port number of the proxy. The default is 8080. Enter an integer value.

User

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

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.

i_round_redOnly basic authentication is available. Enter a string or leave the field empty.

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.

Example

i_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 channel. The additional description text and HTML tags are not necessary. In this example, they are added in case a human calls the URL.

i_round_blueIf you define the number of channels as 1, the sensor only reads the first value. The second value is ignored. Using 3 as the number of channels results in a sensor error message.

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?

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

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

Sensor Settings Overview

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