PRTG Manual: HTTP Advanced Sensor

Sensor Name

Enter a 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.

If the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?

Parent Tags

The tags that the sensor inherits from its parent device, parent group, and parent probe.

This setting is for your information only. You cannot change it.

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.

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

For performance reasons, it can take some minutes until you can filter for new tags that you added.

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 () to the highest priority ().

Timeout (Sec.)

Enter a timeout in seconds for the request. Enter an integer. The maximum timeout value is 900 seconds (15 minutes).

If the reply takes longer than this value, the sensor cancels the request and shows a corresponding error message.

URL

Enter the URL that the sensor connects to.

If you enter an absolute URL, the sensor uses this address independently of the IP Address/DNS Name setting of the parent device. You can enter the URL of a web page (to measure the loading time of the page's source code), or enter the URL of an image or of a page asset to measure this element's availability and loading time.

The URL must be URL encoded.

If you monitor an image or a page asset, this can create a high amount of memory load. We recommend that the size of the elements that you want to monitor does not exceed 200 MB.

PRTG 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.

Request Method

Select an HTTP request method to determine how the sensor requests the URL:

• GET: Directly request the website.
  We recommend that you use this setting for a simple check of the web page.
• POST: Send post form data to the URL.
  If you select this setting, you must enter the data in the Postdata field below.
  If a POST request is redirected, all further requests are GET requests.
• HEAD: Only request the HTTP header from the server without the actual web page.
  Although this saves bandwidth because it transfers less data, we do not recommended that you use this. This is because the measured request time is not the one that your users experience and you might not be notified of slow results or timeouts.

Postdata

This setting is only visible if you select POST above.

Enter the data part for the POST request.

No Extensible Markup Language (XML) is allowed here.

Content Type

This setting is only visible if you select POST above.

Define the content type of the POST request:

• Default (application/x-www-form-urlencoded): Use the default content type to encode the form data set for submission to the server.
• Custom: Use a custom content type. Enter the content type below.

Custom Content Type

This setting is only visible if you select Custom above.

Define the custom content type, for example, XML, JavaScript Object Notation (JSON), or HTTP.

Server Name Indication

The Server Name Indication (SNI) that the sensor automatically determines from the host address of the parent device or from the target URL of the sensor.
The SNI must be a fully qualified domain name (FQDN). Make sure that it matches the configuration of the target server.

For details, see the Knowledge Base: My HTTP sensors fail to monitor websites which use SNI. What can I do?

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

SNI Inheritance

Define if you want to inherit the SNI from the parent device:

• Inherit SNI from parent device: Determine the SNI from the host address of the parent device.
• Do not inherit SNI from parent device: Determine the SNI from the target URL as defined in the settings of this sensor.

Monitoring Engine

Choose the monitoring engine that the sensor uses:

• Default engine (recommended): Use the default monitoring engine.
• Compatibility engine: Execute an external executable program. Use this method as an alternative for websites that do not work with the default monitoring engine.
  This method needs more resources but it can be helpful in some cases.
  If you select the compatibility mode, the options for the SSL method are different. You can also check for trusted certificates. See below.
  Smart URL Replacement does not work with the compatibility mode, so this sensor does not automatically use the IP Address/DNS Name of the parent device.

SSL/TLS Method

This setting is only visible if you select Compatibility engine above.

Select the SSL/TLS method:

• SSLv3
• TLS 1.0, TLS 1.1, TLS 1.2
• SSLv3, TLS 1.0, TLS 1.1, TLS 1.2 (default)

Check SSL Certificates

This setting is only visible if you select Compatibility engine above.

Specify if the sensor checks the certificate of the URL:

• Do not check certificates (default): Do not check the certificates of the web pages.
• Check if certificates are trusted: Check the certificates of the web pages. If the certificate of the server is not trusted, the sensor shows the Down status and displays a corresponding message.

HTTP Version

Define the HTTP version that the sensor uses when it connects to the target URL:

• HTTP 1.0: Use HTTP version 1.0.
• HTTP 1.1: Use HTTP version 1.1.

User Agent

Choose which user agent string the sensor sends when it connects to the target URL:

• Use the default string: Do not enter a specific user agent and use the default string. Usually, this is Mozilla/5.0 (compatible; PRTG Network Monitor (www.paessler.com); Windows).
• Use a custom string: Use a custom user agent. Define the custom user agent below.

Custom User Agent

This setting is only visible if you select Use a custom string above.

Enter the string that the sensor uses as the user agent when it connects to the target URL.

HTTP Headers

Define if you want to send custom HTTP headers to the target URL:

• Do not use custom HTTP headers: Do not use custom HTTP headers.
• Use custom HTTP headers: Use custom headers. Define below.

Custom HTTP Headers

This setting is only visible if you select Use custom HTTP headers above.

Enter a list of custom HTTP headers and values that you want to transmit to the URL, each pair in one line. The syntax of a header-value pair is header1:value1

The sensor does not support the header field names user-agent, content-length, and host.

Make sure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.

If Content Changes

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

• Ignore (default): Do nothing.

• Trigger 'change' notification: Send an internal message that indicates a change.
  In combination with a change trigger, you can use this to trigger a notification if a change occurs.

Require Keyword

Define if the sensor checks the result at the URL for keywords:

• Do not check for keyword (default): Do not search for keywords in the result.
• Set sensor to warning status if keyword is missing: Check if a keyword exists in the result. If it exists, set the sensor to the Warning status.
• Set sensor to down status if keyword is missing: Check if a keyword exists in the result. If it exists, set the sensor to the Down status.

The content check is only intended for HTML websites and might not work with other target URLs. For example, binary files are not supported.

This sensor loads the source code at the URL. If you set up a content check, only this source code is checked for the keywords. The code is not necessarily identical to the code used to display the page when opening the same URL in a web browser. This is because a reload might be configured or certain information might be inserted after loading, for example, via JavaScript.

PRTG does not follow links to embedded objects nor does it execute scripts. Only the first page at the URL is loaded and checked against the expressions configured.

Response Must Include

This setting is only visible if you select Set sensor to warning status if keyword is missing or Set sensor to down status if keyword is missing above.

Define the search string that must be part of the source code at the URL. You can enter a simple string in plain text or a regular expression (regex).

If the source code does not include the search pattern, the sensor shows the status defined above.

The search string must be case sensitive.

Search Method

Define the method with which you want to provide the search string:

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.
You can also search for HTML tags.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Exclude Keyword

Define if the sensor checks the result at the URL for keywords:

• Do not check for keyword (default): Do not search for keywords in the result.
• Set sensor to warning status if keyword is found: Check if a keyword exists in the result. If it exists, set the sensor to the Warning status.
• Set sensor to down status if keyword is found: Check if a keyword exists in the result. If it exists, set the sensor to the Warning status.

The content check is only intended for HTML websites and might not work with other target URLs. For example, binary files are not supported.

Response Must Not Include

This setting is only visible if you select Set sensor to warning status if keyword is found or Set sensor to down status if keyword is found above.

Define the search string that must not be part of the source code at the specified URL. You can enter a simple string in plain text or a regular expression.

The search string must be case sensitive.

If the data does include this string, the sensor shows the status defined above.

Search Method

Define the method with which you want to provide the search string:

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.
You can also search for HTML tags.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Download Limit (KB)

Enter the maximum amount of data (in kilobytes) that is transferred per request.

If you set content checks, be aware that they might be incomplete because only the content downloaded up to this limit is checked for search expressions.

Result Handling

Define what the sensor does with the data loaded at the URL:

• Discard result: Do not store the sensor result.

• Store result: Store the last result of the requested data in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file names are Result of Sensor [ID].txt, Result of Sensor [ID]-A.txt, and Result of Sensor [ID].Data.txt. This setting is for debugging purposes, especially in combination with content checks. PRTG overwrites these files with each scanning interval.

For debugging, select Store result to write the source code file to disk and to look up what exactly PRTG gets when it calls the URL. If the URL does not point to a web page but to a binary file, for example, to an image, you usually do not check for content.

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

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

Authentication

Define if authentication is necessary on the web page:

• Web page does not need authentication
• Web page needs authentication

User Name

This setting is only visible if you select Web page needs authentication above.

If the proxy requires authentication, enter the user name for the proxy login. Enter a string.

Password

This setting is only visible if you select Web page needs authentication above.

Enter a password.

Authentication Method

This setting is only visible if you select Web page needs authentication above.

Select the authentication method that the URL uses:

• HTTP authentication: Use simple HTTP authentication.
  This authentication method transmits credentials as plain text.
• NT LAN Manager authentication: Use the Microsoft NT LAN Manager (NTLM) protocol for authentication.
• Digest access authentication: Use digest access authentication. This applies a hash function to the password, which is safer than HTTP authentication.

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.

You can set a different primary channel later by clicking 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.
  You 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. 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.

Bytes Received

The number of bytes received

Download Bandwidth

The download speed

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

Loading Time

The loading time

This channel is the primary channel by default.

Time To First Byte

The time to the first byte