<%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.
The sensor can show the following:
- Returned numbers in dedicated channels, one channel for each value
Which channels the sensor actually shows might depend on the monitored device and the sensor setup.
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 Channels
PRTG does not officially support more than 50 channels per sensor. 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.
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.
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Value Type
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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.
The sensor cannot handle string values.
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Number of Channels
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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.
Do not enter a number that is smaller than the number of values returned. Otherwise you get an error message.
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Sensor Settings
Click the Settings tab of a sensor to change its settings.
Usually, 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.
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Sensor Name
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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.
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Parent Tags
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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.
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Tags
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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.
It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).
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Priority
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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).
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Default Tags
httpsensor
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Timeout (Sec.)
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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).
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Script URL
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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.
PRTG 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.
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Value Type
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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.
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This sensor implicitly supports SNI, an extension to the Transport Layer Security (TLS) protocol.
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Content Changes
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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.
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Sensor Result
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Define what PRTG does with the sensor results:
- 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 (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.
This option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.
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Authentication
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Define if authentication is necessary on the web page at the configured URL:
- No authentication needed
- Web page needs authentication
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User
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This field is only visible if you enable Web page needs authentication above. Enter a username. Enter a string.
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Password
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This field is only visible if you enable Web page needs authentication above. Enter a password. Enter a string.
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Authentication Method
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This field 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. This is the default setting and is suitable for most cases.
This 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.
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Primary Channel
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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.
You can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.
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Graph Type
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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.
This option cannot be used in combination with manual Vertical Axis Scaling (available in the channel settings).
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Stack Unit
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This field 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.
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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 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 then see the options described below.
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Click to interrupt the inheritance. See section Inheritance of Settings for more information.
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The proxy settings determine how a sensor connects to a URL. You can enter data for an HTTP proxy server that sensors use when connecting via HTTP or HTTPS.
This setting only affects monitoring and it determines the behavior of HTTP sensors. To change proxy settings for the PRTG core server, see section System Administration—Core & Probes
The 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.
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Name
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Enter the IP address or Domain Name System (DNS) name of the proxy server. If you leave this field empty, no proxy is used.
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Port
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Enter the port number of the proxy. Often, port 8080 is used. Enter an integer value.
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User
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If the proxy requires authentication, enter the username for the proxy login.
Only basic authentication is available. Enter a string or leave the field empty.
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Password
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If the proxy requires authentication, enter the password for the proxy login.
Only basic authentication is available. Enter a string or leave the field empty.
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Click to interrupt the inheritance. See section Inheritance of Settings for more information.
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Scanning Interval
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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.
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If a Sensor Query Fails
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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 shows 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 shows 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 shows 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.
Sensors 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 does not apply to these sensors. All other options can apply.
If you define error limits for a sensor's channels, the sensor immediately shows a Down status. No "wait" option applies.
If a channel uses lookup values, the sensor immediately shows a Down status. No "wait" options apply.
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You 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 settings here. They are active at the same time as the parent objects' settings.
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Schedule
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Select a schedule from the list. Schedules can be used to monitor for a certain time span (days or hours) every week.
You can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.
Schedules are generally inherited. New schedules are added to schedules that you already set up, so all schedules are active at the same time.
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Maintenance Window
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Specify if you want to set up a one-time maintenance window. During a maintenance window, the selected object and all child objects are not monitored. They are in a Paused status instead. Choose between:
- Not set (monitor continuously): No maintenance window is set and monitoring is always 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 an active maintenance window.
To terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.
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Maintenance Begins
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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.
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Maintenance Ends
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This field 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 maintenance window.
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Dependency Type
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Define 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 a Down status or in a Paused status caused by 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 a 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.
To 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.
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Dependency
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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 object will depend.
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Dependency Delay (Sec.)
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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 is additionally delayed by the defined time span. This can prevent false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.
This 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.
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Click to interrupt the inheritance. See section Inheritance of Settings for more information.
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User Group Access
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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.
For more details on access rights, see section Access Rights Management.
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Example
For 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.
If 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/
Smart 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?
How can I monitor internal values of a web application with PRTG?
My HTTP sensors don't work. What can I do?
Edit 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: